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Chemical Indicator (chemical monitor, steri l izer c ontrol, chemical control
device, steri l izat ion-process monitoring device ): A steri l izat ion-process
monitoring device designed to respond with a characterist ic and visible
chemical or physical change to one or more parameters of a steri l izat ion
process.
Chemical Integrator: Chemical indicator that reacts to a variety of
steri l izat ion parameters.
Chemosteri l izer (chemical steri lant): Chemical used for the purpose of
destroying all forms of microbiological l i fe, including bacterial spores. The
same chemical used for shorter exposure periods and/or at a lower
concentrat ion may be used for disinfect ion.
P.957
Cleaning: Removal of foreign material from an item.
Contamination : State of actually or potential ly having been in contact with
microorganisms.
Crit ical I tem: Item that penetrates the skin or mucous membranes or is in
contact with normally steri le areas of the body.
Decontamination : A process that renders contaminated inanimate items safe
for handling by personnel who are not wearing protect ive att ire ( i.e.,
reasonably free of the probabil i ty of transmitt ing infect ion) (2,3,4).
Decontamination can range from simple cleaning to s teri l izat ion.
Disinfectant: Chemical germicide formulated to be used on inanimate objects.
Disinfection: Process capable of destroying most microorganisms but, as
ordinari ly used, not bacterial spores. A disinfectant is usually a c hemical
agent, but some processes (such as pasteurizat ion) are disinfect ing. The
Centers for Disease Control and Prevention (CDC) has adopted a
classif icat ion that includes three levels of disinfect ion.
High-level Disinfect ion : A procedure that ki l ls all organisms with the
exception of bacterial spores and certain species, such as the Creutzfeldt-
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Jakob prion. Most high-level disinfectants can produce steri l izat ion with
suff icient contact t ime.
Intermediate-level Disinfect ion: A procedure that ki l ls v egetat ive bacteria,
including Mycobacterium tuberculosis, most fungi, and viruses but not
bacterial spores (5).
Low-level Disinfect ion : A procedure that ki l ls most vegetat ive bacteria (but
not M. tuberculosis), some fungi, and viruses but no spores (5).
Disposable: Intended for use on one patient during a single procedure.
Fungicide: An agent or process that ki l ls fungi.
Germicide: An agent that destroys microorganisms.
Mechanical Monitor(physical moni to r, ph ysical ind ic ato r): Steri l izer
component that gauges and records time, temperature, humidity, or pressure
during a steri l izat ion cycle.
Noncrit ical I tem: An i tem that does not ordinari ly touch the patient or only
touches intact skin but not mucous membranes (5).
Nosocomial: Pertaining to a health care facil i ty. A nosocomial infect ion is
one acquired in a health care fac il i ty.
Permissible Exposure Limit (PEL): The time-weighted average maximum
concentration of an air contaminant to which a worker can be exposed
according to Occupational Safety and Health Administration (OSHA)
standards.
Prions : Proteinaceous infect ious agents with no associated nucleic acids.
Processing: All of the steps performed to make a contaminated device ready
for patient use.
Pseudoinfection : A posit ive culture without cl inical infect ion.
Pyrogens : Substances that can produce fever.
Reprocessing: Decontamination and repackaging of a device that h as been
used for its intended purpose and is labeled for single use (6).
Resteri l izat ion: Steri l izat ion of an unopened ( i.e., inner wrap st i l l intact,
and therefore, the device is presumably unused) steri le device or an
unused wrapped steri le device that is past the expirat ion date.
Reusable : Intended for repeated use either on the same or different patients,
with appropriate reprocessing between uses.
Sanit izat ion: Process of reducing the number of microbial contaminants to a
relat ively safe level. In general, sanitat ion is used for noncrit ical surfaces or
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for applicat ions in which stronger microbial agents may cause device
materials to deteriorate (4).
Sanitizer: A l ow-level disinfectant.
Semicrit ical I tem: A device that is intended to come in contact with mucous
membranes or in tact skin but wil l no t normally come into contact with steri le
t issues.
Short-term Exposure Limit(STEL): A 15-minute t ime-weighted average
exposure that should not be exceeded at any time during a work day.
Spore: The normal rest ing stage in the l i fe cycle of ce rtain bacteria.
Sporicide: An agent that ki l ls spores.
Standard Precautions : Policies promulgated by the Centers f or Disease
Control and Prevention (CDC) in 1996 that include universal precautions,
airborne precautions, droplet precautions, and contact precautions. Standard
precautions apply to all pat ients, regardless of their diagnosis or known or
presumed infection status.
Steri lant/Disinfectant: Term applied by the Environmental Protect ion Agency
(EPA) to a germicide that is c apable of steri l izat ion or high-level disinfect ion.
Steri le/Steri l i ty: State of being free from all l iving microorganisms. In
pract ice, steri l i ty is usually described in terms of the steri l i ty assurance
level.
Steri l i ty Assurance Level(SAL): Probabil i ty that microorganisms wil l survive
after a terminal steri l izat ion process. Before a manufacturer can label a
product as steri le, i t must have a steri l i ty assurance level of 10 - 6, which
means that the possibil i ty that microorganisms have survived on the item
exists but is no greater than 1 10- 6
or 1 in 1,000,000.
Steri l izat ion: Process capable of removing or destroying all viable forms of
microbial l i fe, including bacterial spores, to an acceptable steri l i ty assurance
level.
P.958
Terminal Steri l izat ion : Steri l izat ion process that is carried out after an item
has been placed in i ts f inal packaging.
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Threshold Limit Value Ceil ing: Concentrat ion of an air c ontaminant to which
it is believed that nearly all workers may be repeatedly exposed day after
day without adverse effect.
Time-weighted Average (TWA): Integrat ion of all the concentrat ions of a
chemical to which a worker has been exposed during a sampling period,
reported as an average.
Transmission-based Precautions: Recommendations by the CDC for patients
with known or suspected infect ion or colonization with highly transmissible or
epidemiologically important pathogens that can be transmitted by airborne or
droplet transmission or by contact with dry ski n or contaminated surfaces.
Tuberculocide : An agent or process that ki l ls tubercle bacil l i .
Universal Precautions : Recommendations made by the CDC that health care
workers consider blood and certain body f luids to be po tential ly infect ious for
bloodborne pathogens and use protective barriers and workplace practices to
reduce the risk of exposure. In 1996, universal precautions were
incorporated into standard p recautions, which expanded the coverage to any
body f luid that may contain contagious microorganisms.
Vegetative : Active growth phase of a microorganism.
Virucide: Agent that inact ivates viruses.
Virus : Submicroscopic, noncellular part icle composed of a protein shell and a
nucleic acid core, and, in c omplex types, a surrounding envelope. In broad
terms, viruses are either l ipophil ic (enveloped) or hydrophil ic (naked) (7).
Role of the Federal Government and Professional
Associations
The EPA registers and regulates chemical germicides (8,9). I t requires
manufacturers to test formulat ions of chemical germicides for microbicidal potency
(eff icacy), stabil i ty, and toxicity. I t also a pproves s teri l izat ion devices.
The Food and Drug Administrat ion (FDA) regulates medical devices and considers
liquid chemical germicides used to reprocess medical instruments as accessories to
medical devices. The FDA requires that the manufacturer of a device marketed as
reusable provide the user with adequate instruct ions for cleaning and disinfect ing
or steri l izing the item.
In 1993, the FDA and EPA signed a memorandum of understanding that states that
the agencies wil l divide the premarket clearance of germicides so that the FDA
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would clear liquid chemical sterilants and the EPA would register general-purpose
disinfectants before marketing (9A).
OSHA regulates occupational exposure to chemical disinfectants and steri l izers.
The CDC does not approve, regulate, or test germicides or s teri l izers. Rather, i t
recommends broad strategies to prevent transmission of infect ions in the health
care environment.
Practices and procedures to reprocess reusable devices have been published by
several professional organizations, including the American Society of
Anesthes iolog is ts (ASA), the Ame ric an As sociati on of Nurs e Anesthetis ts (AANA ),
and the Associat ion of Operating Room Nurses (AORN) (2,10 ,11).
Resistance of Microorganisms to Disinfection andSterilization
Microorganisms can be categorized into groups according to their innate resistance
to a s pectrum of physical processes o r chemical germicidal agents. Figure 34.1
shows a general descending order of microbial resistance levels. Resistance to
disinfect ion and steri l izat ion is not equivalent to resistance to antibiot ics. For
example, antibiot ic-resistant strains of staphylococci do not appear to be more
resistant to chemical germicides than nonresistant bacteria (8).
Cleaning
The f irst and most important step in decontamination is thorough cleaning
(12,13,14). In s ome cases, cleaning may be suff icient to render an i tem suitable for
reuse. I f an art icle is not c lean, retained salts and organic soil could inactivate
chemical germicides or protect microorganisms during the disinfect ion or
steri l izat ion process. Even if the item is rendered steri le, residues may interfere
with the device's function or cause a reaction in a patient.
I t is important to prevent blood or other body f luids from drying on devices.
Enzymatic foam sprays that prevent drying, break down blood and protein, and
inhibit bacterial growth are available. Flushing lumens with enzymatic cleaner wil l
break up debris. I tems that can be immersed should be soaked in water plus an
enzyme presoak with or without detergent for at least 3 minutes (15 ). Stainless
steel or other metal devices should not be soaked in saline or s odium hypochlorite
solut ions, because the chloride ions in these two s ubstances wil l cause the metal to
corrode (13). A c losed container should be used to move contaminated devices to
the decontamination area.
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P.959
View Figure
Figure 34.1Descending order of resistance of organisms.
Cleaning should be performed in a designated location that is separate from other
parts of the facil i ty to minimize inadvertent personnel exposure or exposure of
other items to contaminants. The area sh ould be restricted to authorized personnel
as much as possible. I t should be away from traff ic, pat ients, and clean-item
storage. The f loors, walls, ceil ing, and work surface should be made of non-porous
materials that wil l not s upport the growth of mold. These surfaces should be
washed frequently. The area should have adequate lighting with no shadowed or
dark areas. The f loor should be designed to prevent sl ipping but be easy to clean.
Horizontal work surfaces should be cleaned and disinfected daily. Fluid spil ls
should be cleaned up quickly to prevent sl ips and falls. I f the spil led material was
contaminated with blood, the spil l area should be treated after it has been cleaned
up with a tuberculocidal germicide.
The heating, venti lat ion, and air-condit ioning systems should be designed to
minimize spreading contaminants to adjacent spaces. The air pressure within the
decontamination space should be negative relat ive to the surrounding spaces so
that air does not f low out of the area. There should be a minimum of 6 to 10 total
air exchanges each hour with 100% fresh air. Air from this area should be
exhausted to the outside without recirculat ion or to a f i l tered part ial recirculat ing
system.
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The area should be divided into dirty and clean areas. Signs showing where dirty
equipment is to be placed should be prominently displayed. Sinks should be big
enough to contain large instruments, and there should be enough sinks to
accommodate concurrent soaking, washing, and rinsing. Sinks should have
attached c ounters or adjacent work surfaces on which to place soiled and clean
items separately. Hand-washing facil i t ies s hould be conveniently located in or near
the decontamination area. Personnel should wear a full complement of protective
attire (hair covering, fluid-resistant mask, eyewear, waterproof gown or apron,
appropriate gloves, and waterproof shoes or boots with n onskid soles) (13 ,16 ).
Personnel should be careful not to injure themselves with contaminated
instruments.
Each device manufacturer's instruct ions should be c onsulted to determine the
appropriate cleaning methods and agents to remove soil without damaging the
device. Tape should be removed and adhesive residue dissolved by using an
appropriate solvent.
P.960
The next step is disassembly (if not done at the source). An init ial water r inse or
soaking with a specialized product (e.g., a protein-dissolving solut ion) can prevent
blood coagulat ion on the device and remove gross debris. The water temperature
should not exceed 45C, because higher temperatures cause proteinaceous soil to
coagulate (17). An alternative is to use a spray-on precleaner to help dissolve the
soil (12).
Af ter the equipm ent has soa ked long eno ugh to loosen orga nic matte r, i t should be
thoroughly sc rubbed inside and out. Part icular attention should be paid to lumens,
crevices, corners, grooves, and knurled or textured surfaces. I t is important to have
a variety of brushes (18 ). Brushes and other cleaning implements should be
disposable or should be cleaned and steri l ized or undergo high-level disinfect ion at
least daily.
Immersible devices cleaned under water to prevent aerosolizat ion of
microorganisms. A cloth soaked i n detergent and water can be used to clean items
that cannot be immersed. Detergents should be low s udsing and rinse off without
leaving a residue. Detergent residues can lead to staining and may interfere with
the act ion of some chemical disinfectants (13).
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Cleaning may be accomplished manually, mechanically, or by a combination of
both. Using mechanical equipment may increase productivity, improve cleaning
effect iveness, and offer greater protect ion for the worker.
A varie ty of wa shing machines are avai la ble (12,19 ). They are highly automated,
usually with microprocessor control. Washer-steri l izers are designed to wash, r inse,
and then steam steri l ize items (4,13). Washer-decontaminators/disinfectors use hot
water in the range of 60C to 95C. They are designed to wash, r inse, and dry the
same items as a washer-steri l izer but can process items that would be deteriorated
by the high temperature used in steam s teri l ization.
Some equipment that has joints, c revices, lumens, and other hard-to-reach areas
can be treated in an ultrasonic cleaning system after gross soil has been removed.
In an u ltrasonic cleaner, high-frequency sound waves passing through a solvent
produce submicroscopic bubbles. These bubbles collapse on themselves,
generating t iny s hock waves that knock debris off surfaces. A detergent is often
added to the ultrasonic l iquid. The water may be heated. Ultrasonic cleaning tanks
are available in a variety of si zes and configurat ions. The equipment to be cleaned
is placed in a basket or tray and into the ultrasonic tank for a preset period of
t imeusually 3 to 6 minutes. Ultrasonic cleaning monitors are available (20 ). Some
manufacturers of delicate instruments, including laryngoscopes, recommend that
they not be subjected to ultrasonic cleaning because the process may loosen f ine
screws and adversely affect alignment (21).
Af ter c lea ni ng , ri ns ing shou ld be perf ormed to remove soil an d re sidual de terg en t
and to keep i t from resett l ing on the equipment. Lumens and channels should be
well f lushed during each rinse. Inadequate rinsing can cause irr itat ion and burns in
patients (22 ). Some items (such as those undergoing plasma sterilization) should
be rinsed with alcohol or dist i l led or demineralized water.
The cleaned item should be thoroughly dried. Even if an item is to undergo no
further processing, drying is important because a humid environment may
encourage the growth of certain organisms. I f a l iquid chemical agent is to be used,
water on the equipment will dilute the agent and make it less effective. If water
droplets remain on equipment that is to be gas steri l ized, ethylene oxide (EO) wil l
dissolve in the water and form ethylene glycol, which is both toxic and dif f icult to
remove. Most items may be towel- or air-dried. Air-drying cabinets and hot-air
ovens are available (Fig. 34.2). If an item is to undergo EO sterilization, unheated
air should be used.
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Af ter c lea ni ng , each i tem shou ld be in spec te d to verif y c lean li ness and te ste d fo r
functionality (23). All accessible surfaces should be examined under normal
l ight ing. Swab tests for detect ing residual protein on surfaces are available.
Disassembled devices must be reassembled to perform functionality testing. After
functionality is verif ied, some devices must again be disassembled to ensure that
the steri lant can contact all the surfaces.
Disinfection and Sterilization Methods
Pas t e u r i z a t i o n
With pasteurization (hot water disinfection), the equipment is immersed in water at
an elevated temperature (but below 100C) for a specified time. The time and
temperature va ry. A typical sequence is 30 minutes at a temperature of 70C.
Contact time is inversely related to temperature, that is, for equivalent microbial
ki l l , a longer exposure t ime is required when the temperature is reduced. CDC
guidelines refer to p asteurizat ion as a high-level disinfect ion process, although
some feel i t is intermediate-level (13,24 ).
Pasteurizing machines come in dif ferent sizes ( Fig. 34.3). Many also wash the
equipment. They are simple to load and operate. Special dryers that a re equipped
with f i l ters are available.
Pasteurization has been used for breathing tubes, reservoir bags, tracheal tubes,
face masks, airways, laryngoscope blades, stylets, bi te blocks, Y-pieces, elbows,
adaptors, and venti lator bellows.
A ma jor advan tage of pas teurizat ion is that the lowe r te mp era tu re is les s damagi ng
to equipment than the higher temperatures employed during autoclaving. There are
no toxic fumes or residues. I t is simple,
P.961
inexpensive, and reliable. This technology may result in considerable savingscompared with throwing equipment away. The main disadvantage is that the treated
equipment is wet and must st i l l be dried and packaged, during which t ime it may
again become contaminated. The heat may damage some materials.
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View Figure
Figure 34.2Forced-air drying cabin for equipment. (Picturecourtesy of Olympic Medical.)
S t eam St e r i l i z a t i o n
Steam steri l izat ion (autoclaving) ut i l izes saturated steam under pressure
(19,25,26,27 ,28 ,29). I t is the most widely used and inexpensive of the steri l izat ion
techniques.
At sea le vel , wa ter boils at 100C . Whe n it is boi led wi thin a clo sed vessel at
increased pressure, the temperature at which it boils and that of the steam it forms
will exceed 100C. The increase in temperature depends on the pressure within the
chamber. Pressure per se has l i t t le or no steri l izing effect. I t is the moist heat at a
suitable temperature, as regulated by the pressure in the c hamber, that b rings
about steri l izat ion.
Increasing the temperature dramatically reduces the t ime needed to achieve
steri l izat ion. The minimum t ime for steri l izat ion by steam at 121C is 15 minutes. I f
the temperature is 126C, the t ime is reduced to 10 minutes.
P.962
It is 3.5 minutes at 134C and only a few seconds at 150C.
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View Figure
Figure 34.3Pasteurization machine. (Picture courtesy ofOlympic Medical.)
Increasing the temperature dramatically reduces the t ime needed to achieve
steri l izat ion. The minimum t ime for steri l izat ion by steam at 121C is 15 min. I f the
temperature is 126C, the time is reduced to 10 min. It is 3.5 min at 134C and only
a few s econds at 150C.
Autoc lav in g is ef fecti ve because the s te am tra nsfers he at to ma te rials ra pi dl y on
contact. Microbial destruct ion wil l be most effect ive at locations where saturated
steam can contact the microorganisms. At locations inaccessible to steam
penetrat ion (as might occur with complex devices, improperly packaged items or
incorrect load configurat ions), some microbial destruct ion may occur, but dry heat
is not as eff icient at steri l izing as saturated steam.
Equipment to be steri l ized is cleaned, and then may be packaged in a material
easily penetrated by steam. After steri l i zat ion, the packaging material prevents
recontamination during subsequent handling and storage.
P.963
Autoclave Design
A ste am ste ri l ize r can ran ge f ro m a sma l l , manually-operate d table to p s te ri l ize r to a
large, computer-controlled, f loo r-loading model (26 ,28,29 ,30 ,31). Steri l izers are
described by the method of air removal, temperature and the time the chamber is
held at the specif ied temperature (e.g., vacuum, 130C, 4 minutes) (28 ).
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The chamber (pressure vessel) is where materials to be steri l ized are placed and
through which steam is circulated. I t must be c onstructed to withstand the high
pressures required to bring the steam up to the temperatures required and f it ted
with a safety valve to prevent development of excessive pressure. Chamber size
varies from less than 1.5 cubic feet in small tabletop steri l izers to more than 70
cubic feet in large f loor-loading models (28 ). The jacket is the port ion surrounding
the chamber. It functions to maintain the temperature in the chamber.
The steri l izer may be equipped with one or two doors. Doors may be hinged or
sliding and are opened and closed manually or by power (electric, pneumatic or
hydraulic). I tems are placed on a shelf in the chamber, and the door closed and
secured.
Ai r must be dis placed f ro m th e chamber. Thi s is called th e cond iti oning or hea t- up
phase (Figure 34.4). I ts length varies, depending on the load. In the gravity-
displacement type of s teri l izer the incoming steam displaces the air through a port
or drain in or near the bottom of the chamber. The steri l izer chamber drain remains
open unti l the temperature in the drain is the same as the t emperature of the steam
entering the chamber, indicating that the air has been removed. The pre-vacuum
steri l izer depends on one or more pressure and v acuum excursions to remove air.
The steam-flush pressure-pulse steri l izer uses a repeated sequence of a steam
flush and a pressure pulse. No vacuum is required. A pre-vacuum or steam-flush
pressure-pulse steri l izer results in shorter cycles because air is removed more
rapidly.
In the gravity-displacement type of steri l izer, the incoming steam displaces the air
through a port or drain in or near the bottom of the chamber. The steri l izer
P.964
chamber drain remains open unti l the temperature in the drain is the same as the
temperature of the steam entering the chamber, indicat ing that the air has been
removed. The pre-vacuum steri l izer depends on one or more pressure and vacuum
excursions to remove air. The steam-flush pressure-pulse steri l izer uses a repeated
sequence of a steam f lush and a pressure pulse (Fig. 34.4). No vacuum is required.
A prevac uum or s team-flus h pres sure-p ulse s te ri l izer re sul ts in shorter cycles
because the air is removed more rapidly.
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View Figure
Figure 34.4Typical steam sterilization cycle. Conditioningphase (A); sterilization phase (B); exhaust phase (C); dryphase (D). (Redrawn from a figure inYoung JH. Steam sterilization: scientific principles. In:Reichert M, Young JH, eds. Sterilization Technology forthe Health Care Facility. 2nd ed. Gaithersburg, MD: Aspen
Publishers, Inc., 1997:124133.)
As steam ente rs the chamber, i t en te rs the load to be ste ri l ize d an d gi ves up i ts
latent heat. Once the intended temperature is reached, the sterilization time is set.
This is called the exposure o r steri l izat ion phase . By convention, steri l izat ion
cycles in health care sett ings have been s tandardized at a few temperature-t ime
relat ionships (29 ). The lowest temperature for a steri l izer is 121C (250F). Cycles
may also be programmed at 132C (270F), 134C (275F), or 145C (285F),
depending on the steri l izer. In general, wrapped items should be steri l ized for 30
minutes and unwrapped items for 20 minutes at 121C ( 32).
Af ter the s te ri l iza t ion phas e, i tems mus t be dried bef ore being remov ed from the
steri l izer. This is called the pos texposure (exha us t, dry) phase and consists of
exhausting the chamber to atmosphere followed by circulat ing f i l tered air through
the chamber or by drawing a deep vacuum (27). Some tabletop autoclaves require
that the door be c racked, but newer models may allow closed-door drying (33,34 ).
Flash steri l izat ion allows items to be s team steri l ized for immediate use (35 ,36 ).
The items to be processed are usually unwrapped. The time and temperature will
depend on the steri l izer and the configurat ion of the load. The processed items are
transferred immediately from the autoclave to the point of use, usually the steri le
f ield in an ongoing surgical procedure.
Problems with Steam Sterilization
P r o b l em s w i t h t h e St e am
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Steam quality or saturation refers to the percentage of liquid in steam. Current
standards call for a steam quality greater than 97% (less than 3% liquid water).
Variations in steam pressure may affect the time needed to attain the proper
temperature and temperature uniformity within the chamber. Clogged f i l ters, poorly
engineered piping, or excessive demands on the steam supply may cause pressure
variat ions. Steam is saturated when it has the proper balance of pressure and
temperature. I f the pressure is too high, the steam wil l change to l iquid, c ausing
packs to become wet; i f the pressure is too low, the s team wil l be superheated.
Superheated steam is less able to transfer its heat e nergy to the cooler items being
steri l ized than saturated steam and wil l interfere with achieving a uniform
temperature in the chamber.
A i r i n t h e A u t o c l a v e Ch amb e r
The presence of air in the chamber wil l impair steri l izat ion. Air conducts heat poorly
and retards steam penetration. The autoclave evacuates much of the air at the
beginning of the cycle (Fig. 34.4). All of the air does not have to be removed, but
all surfaces requiring steri l izat ion must be exposed to adequate moisture (27 ).
Improper steri l izer loading and incorrect ly prepared individual packages can affect
the abil i ty of the steri l izer to remove air from the load (37 ).
Many autoclaves have a built- in vacuum leak test ( 37 ). Such steri l izers are c apable
of running a special c ycle that pauses when the maximum vacuum is achieved. For
others, the eff icacy of the air removal process can be tested by a Bowie-Dick test.
This is run with a s ingle test pack in the chamber. This should be run each day
before the f irst steri l izat ion cycle (20 ,38). Air detection devices may be added to
the steri l izer plumbing and c ontrol system.
E q u i pm e n t M a lf u n c t i o n
Examples of equipment malfunction include out-of-calibration temperature or
pressure gauges and controllers, incorrect steam supply pressure, faulty or
maladjusted control valves, leaks, clogged vent l ines or drain screens, faulty
vacuum pumps, defect ive steam traps, and malfunctioning cycle sequence
controllers.
Per s o n n e l E r r o r s
Personnel errors include inadequate cleaning, incorrect pack preparation o r
packaging methods, and poor loading techniques (39). I tems in the steri l izer must
be posit ioned so that air c annot be trapped. I tems should not be crowded or stuffed
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into the autoclave. Crowding may interfere with both air el imination and drying. I f
the shape of an item would allow water to collect in any part, that item should be
posit ioned on its side or upside down so that the water can run out. I f water can
pool, then air could be trapped against the surface.
Steam Sterilization Monitoring
Steri l izat ion validat ion is achieved by using a c ombination of mechanical, chemical,
and biological indicators (19 ,40). Using these in concert wil l g ive the greatest
possible confidence that items are s teri le.
Me c h a n i c a l I n d i c a t o r s
Mechanical monitors indicate time, temperature, and pressure (37 ). Most
autoclaves provide a permanent record of these parameters. The temperature in a
f loor-loading steri l izer is typically measured in the chamber drain piping. In small
tabletop steri l izers where the s team is generated within the chamber, the
temperature is usually measured in the chamber. Some tabletop steri l izers do not
have a recorder. With
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these, it is important to monitor physical condit ions during the cycle (39 ).
View Figure
Figure 34.5Autoclave tape is an example of an externalprocess indicator. The exposed tape is at top.
Ch em i c a l I n d i c a t o r s
Chemical indicators are divided into f ive classes (41 ,42,43,44). The higher the
class, the more sensit ive the indicator.
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Class 1 i ndicators are i nternal and external process indicators. These inform the
user that the item has been exposed to the steri l izat ion process. The most common
example of an external process indicator is autoclave tape (Fig. 34.5). Most tapes
do not respond to al l the parameters of steri l izat ion but do offer visual proof that
the pack has been through the process. Internal process indicators usually exhibit a
color change from white to black. Like autoclave tape, they have l imi ted sensit ivity
to the parameters of steri l izat ion but do i ndicate exposure to steam.
Class 2 i ndicators relate to the Bowie-Dick test for vacuum steam steri l izers. They
do not determine if the steri l izat ion parameters have been met but only assess
vacuum pump efficiency and detect the presence of air leaks and/or gases in the
steam. The indicator is placed in a pack of towels (handmade or purchased) on the
front bottom shelf over the drain and a 3.5- to 4 -minute cycle is run. Many new
steri l izers are equipped with leak test c ycles, so these indicators do not need to be
used.
Class 3 i ndicators are si ngle parameter. An example is the temperature tube that
contains a chemical that melts and sometimes changes color when the appropriate
temperature is attained. These indicators are helpful in determining if the
appropriate temperature was achieved in the center of large packs. False-positive
results have been reported (43).
Class 4 i ndicators respond to one or more steri l izat ion parameters. They contain an
ink that changes color when exposed to the correct combination of s teri l izat ion
parameters.
Class 5 i ndicators are also known as integrat ing indicators or integrators. They
respond to all parameters of steri l izat ion over a specif ied range of temperatures.
False-posit ive and false-negative results have been reported (41 ).
Chemical indicators can detect fai lures or errors in packaging, pack density,
loading, insufficient humidification, inadequate exposure time at the selected
temperature, or sterilizer malfunction. An important advantage is that they can be
read as soon as the packs have been opened. Another advantage is that they are
so inexpensive that one can be used in every pack.
The CDC and a ll major U.S. o rganizations that issue steri l izat ion-related standards
or guidelines advocate that a chemical indicator be attached to every package that
goes through a steri l izat ion cycle and within e ach package to be steri l ized in what
is expected to be the most dif f icult-to-steri l ize location.
There are both U.S. (45,46 ,47 ) and international (48 ,49,50,51,52,53) standards for
chemical indicators.
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B i o l o g i c a l In d i c a t o r s
Biological indicators are standardized preparations of spores (typically str ips or
ampoules) that are placed in the most dif f icult-to-steri l ize location(s) in the load
(37,43). Alternatively, a biological indicator that is enclosed in a commercial test
pack can be used. The indicators are exposed to the steri l izat ion cycle, retr ieved,
incubated, and examined for microbial growth. A posit ive b iological indicator is
indicat ive of a possible steri l izat ion process failure. Commercial mail- in biological
monitoring services eliminate the need for on-site incubation.
One type of b iological indicator contains a rapid detect ion system that is based on
the interact ion of an enzyme in the bacterial spore with a substrate in the growth
medium. Fluorescence occurs when the viable biological indicator is exposed toultraviolet light. This type of indicator can be read in 3 hours with a wrapped item
or in 1 hour with an unwrapped item. It may be particularly useful in the operating
or ambulatory sett ing where products are often steri l ized unwrapped in a gravity
displacement steri l izer (43 ,54).
The main problem with biological indicators is the t ime needed for incubation.
Biological monitors should be used at least once a week but preferably daily a nd
after major repairs to the steri l izer ( 37,43 ).
There are both U.S. (55,56 ,57 ,58,59 ) and international (60,61,62,63) standards for
biological indicators.
Advantages and Disadvantages of Autoclaving
Steam autoclaving can kil l al l bacteria, viruses, and spores. Advantages include
speed, good penetrat ion, economy, ease of use, absence of toxic products or
residues, and reliabil i ty. The material can be prepackaged and kept steri le unti l
used. I t poses no harm to
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the environment. A major advantage is that at least one autoclave is available in
every modern operating theater.
The principal disadvantage of autoclaving is t hat many pieces of equipment are
damaged if subjected to steam. Autoclaving can cause blunted cutting edges, metal
surface corrosion, and shortened l i fe of electronic components. Fiber-optic
laryngoscope blades show a decrease in l ight transmission with repeated
autoclaving (64 ).
Dry Hea t St e r i l i z a t i o n
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Dry heat is used for items that might be damaged by moist heat ( 65 ,66 ,67 ). While
slow, this technique penetrates well and does not corrode metal and sharp
instruments (68 ). I t is useful for nonaqueous l iquids or semisolids such as talc,
glycerin, oils, petroleum jell y, waxes, and powders.
Times and temperatures frequently used for dry heat steri l izat ion are 170C for 60
minutes, 160C for 120 minutes, and 150C for 150 minutes (32 ,68). Some of the
newer dry heat steri l izers can attain temperatures up to 210C (65). Convection hot
air steri l izers improve heat transfer by using forced air. These units have
comparatively fast cycle t imes.
There are both U.S. and international standards for biological indicators for dry
heat steri l izat ion processes (69).
Chem i c a l D i s i n f e c t i o n and S t e r i l i z at i o n
Chemical (cold) disinfect ion/steri l ization involves immersing an item in a solut ion
that contains a disinfectant (3). This method is especially useful for heat-sensit ive
equipment. I t can be accomplished by automated equipment, which typically
provides a cycle of cleaning, r insing, disinfect ion, r insing, and sometimes drying.
Regulation and Labeling
The EPA regulates formulat ions and labeling of c hemical germicides (70). The
labeling must p rovide c ertain information, including precautionary statements,
directions for use, the required contact time, recommended use temperature, use
pattern, use l i fe, and shelf l i fe. The EPA also requires that the label show the
abil i ty of the chemical agent to destroy certain organisms such as M. tuberculosis.
I t is imperative that the user str ict ly fol lows the direct ions provided by the
manufacturer.
The FDA clears l iquid chemical steri lants. The current l ist ing of cleared l iquid
chemical steri lants and the t ime-temperature claims for steri l izat ion and high-level
disinfect ion can be accessed at http://www.fda.gov/cdrh/ode/germlab.html .
Factors Influencing Chemical Disinfection
Co n c e n t r at i o n o f t h e Ch em i c a l
In general, higher concentrat ions of the ac t ive ingredients increase the
disinfectant 's bactericidal abil i ty. An exception is the alcohols. However, extremely
high concentrat ions increase the potential for damage both to inanimate objects
and to the sk in and mucous membranes of p ersonnel. For best results, products
should be used according to the manufacturer's recommendations.
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Water left on equipment wil l di lute the chemical and render it less effect ive. Dilut ion
can become signif icant with frequent reuse and can reduce the concentration to a
level that is too low to be effect ive. For this reason, equipment should be dried
before undergoing chemical disinfect ion or s teri l izat ion. In some cases, the
technique (manual or automatic) may determine how fast the co ncentrat ion falls
(71).
Tempe r a t u r e
Higher temperatures usually increase the effect iveness of chemical agents. Special
devices are available for heating some chemical solut ions. Too high a temperature
may cause the act ive ingredients to evaporate or degrade. The label should tell
which temperature should be used.
E v a p o r a t i o n a n d L i g h t D e ac t i v a t i o n
I f the solut ion is in an uncovered container, evaporation can occur. Usually,
evaporation is not as serious as dilut ion. However, i f the chemical agent is more
volat i le than the diluent, loss by evaporation can be very important. Chlorine
products are especially susceptible to evaporation and deactivat ion from exposure
to l ight.
B i o b u r d e n
In general, the higher the level of microbial contamination, the longer the exposure
to the chemical germicide necessary before the entire microbial populat ion is ki l led.
Thus, items should be scrupulously cleaned. Liquid agents vary widely in their
effect iveness against various types of microorganisms. Table 34.1shows the
capabil i t ies of s ome commonly used agents.
p H
The relat ive acidity or alkalinity of disinfectants can inf luence the biocidal act ivity.
An inc reas e in pH tends to decre as e the eff icac y of ph eno ls, iod ine , and
hypochlorites. In contrast, i t wil l improve the antimicrobial act ivity of glutaraldehyde
and quaternary ammonium compounds. Soluble c alcium or magnesium in the water
supply can react with detergents to form insoluble precipitates, which tend to
neutralize some disin-fectants (4).
Ch a r a c t er i s t i c s o f t h e It em t o B e D is i n f e c t e d
A dis inf ecta nt so lu ti on wi l l be effec ti ve on ly if i t can con tac t al l surfa ces (inn er an d
outer) of the item to be disinfected (72 ). Uneven or porous surfaces resist chemical
disinfect ion. Air
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entrapment can prevent contact between the liquid and parts of the device.
TABLE 34.1 Capabilities of Disinfecting Agentsa,b
Disinfectant Gram-
Positive
Bacteria
Gram-
Negative
Bacteria
Tubercle
Bacillus
SooresVirususFungi
Quaternary ammonium
compounds
+ 0 0
Alcohols + + + 0
Glutaraldehydes + + + + +
Hydrogen peroxide-based compounds
+ + + + +
Formaldehyde andother agents
+ + + - + +
Phenolic compounds + + 0
Chlorine + + + - + +
aFrom Chatbum RL. Decontamination of respiratory care equipment what can be
done, what should be done. Respir Care 1989:34:98; and Berry AJ. Infection control in
anesthesia. Anesth Clin North AM 1989;7:967981.
b+, good; , fair, 0, little or none.
Use Pa t t e r n , U s e L i f e , an d S t o r a g e L i f e
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The product label should be examined for information on the use pattern, use l i fe,
and storage l i fe. Use pattern refers to how many t imes the solut ion can be used.
Use l i fe commonly applies but is not l imited to disinfectant products that applies,
but is not l imited to, require mixing of two ingredients for act ivat ion. Once a
disinfectant solut ion is mixed, there wil l be a l imited period of t ime during which the
activated solut ion may be used. The container should be marked with the date the
solut ion was prepared and the date it expires. The storage l i fe is the t ime period
after which the u nused and/or unactivated product is no l onger deemed effect ive.
T im e
The t ime required for dif ferent chemical agents to function effect ively varies from
seconds to hours and wil l depend on the factors just mentioned. Somemicroorganisms are killed faster than others. Contact time may make the difference
between steri l izat ion and high-level disinfect ion. For high-level disinfect ion, a
minimum contact t ime of 20 to 30 minutes is recommended (3). A lower level of
disinfect ion can be achieved in less t ime. Leaving devices in the disinfectant too
long can make it harder to r inse off the chemical (22 ).
Safe Practices
Designated areas for chemical disinfect ion s hould be strongly encouraged
(2,5 ,73 ,74,75,76,77,78,79,80,81 ). Ideally, the area used for cleaning should beseparate from the space where the chemical is used. Both of these spaces should
be separate from patient p rocedure and personnel support areas. Traff ic should b e
limited to trained personnel.
Chemical disinfectants should be used in an area that is large enough to ensure
adequate vapor dilution with an air exchange rate not less than 10/hour. The fresh
air inlet should be p laced across the room from the local exhaust venti lat ion.
Local exhaust venti lat ion (either a ductless system or a ducted fume hood) should
be installed to capture chemical vapors. A ducted fume hood should be connected
to a non-recirculat ing exhaust system that goes to the outside atmosphere at a
location away from people and air in take ducts. Self-contained (ductless) fume
hoods (Fig. 34.6) encapsulate the soaking container and have a blower that draws
fumes away from the operator and delivers them to a s ystem that chemically
inactivates the germicide and returns clean f i l tered air to t he room. This eliminates
the need to install a duct.
The employer should provide training to each employee who handles germicides
and verify that each employee has received and understood the required training.
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Automated processing equ ip ment can reduce ex posure to ge rm icides. Hoods
designed for automatic washing machines are available.
Personnel should wear appropriate protective equipment designed to protect the
skin, eyes (goggles or ful l face shields), and clothing from splashes when using
chemical germicide solut ions. Impervious gloves and gowns should be worn. T he
user should double glove and/or change single gloves frequently. Protect ive
clothing should be removed quickly if i t becomes saturated and should be
laundered before reuse. There should be ready access to means to decontaminate
the eyes and skin in the event of contact with the solut ion.
During preparation and act ivat ion of germicide solut ions, every effort should be
made to minimize splashing, spil l ing, and personnel exposure. The chemical should
be kept in a closed container with a t ight-f i t t ing l id. Agitat ion and splashing should
be avoided when the solut ion is poured. Safety nozzles can be used to
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reduce the exposure to v apors created when pouring solut ions.
View Figure
Figure 34.6Glutaraldehyde user station. Fumes are drawnaway from the operator and into a filter, where they areneutralized.
I f i t is necessary to transport an act ivated solut ion, a method of transportat ion that
wil l minimize the potential for spil ls and the possibil i ty of personnel exposure to the
solut ion or vapor should be selected. Transport ing solut ions in containers such as
trays or buckets should be av oided.
The disinfectant solut ion should be stored in a t ight ly closed container in a well-
ventilated area. Containers that minimize the surface area should be used. The lid
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should be kept on the c ontainer at a ll t imes except when items are placed i nto or
removed from the solut ion.
Items should be immersed in the chemical solut ion gently, taking care to disturb
and agitate the surface as l i t t le as possible. When the solut ion must be manually
irr igated or f lushed through internal channels or lumens, care should be taken to
avoid splashing. The syringe should be carefully f i l led with the solut ion and
securely attached to the channel opening or all-channel irr igator and the solut ion
pushed slowly.
Items should be gently removed from the solution and rinsed thoroughly in clean or
steri le water. Rinse water should be discarded promptly, not reused. Semicrit ical
items should be rinsed with steri le water to prevent organisms that may be in tap
water from contaminating them. Alternately, the items may be rinsed f irst with tap
water and then with alcohol.
Discarding a chemical solut ion involves high risk of employee exposure. The
solut ion should be discarded, along with copious amounts of c old water into a drain
connected to a sanitary se wer. Chemical germicide solut ions should not be
discarded into septic s ystems.
A spi ll conta inment re spon se team shou ld be created and be res po ns ible for
developing and executing procedures for chemical spil ls. I f there is a chemical that
can be used to neutralize the germicide and reduce ambient vapor levels in spil l
situat ions, it should be readily available.
Small spil ls and droplets can be absorbed and neutralized by using special mats
that are highly absorbent and treated with the neutralizing chemical. Alternately,
they can be wiped up quickly with a sponge, towel, or mop that has been
neutralized with an appropriate chemical agent and then wiped up. The sponge,
towel, or mop should be thoroughly r insed with large amounts of water and the
water discarded through the drain.
Larger spil ls are best treated by using chemical spil l kits that include an approved
deactivator/neutralizer to pour over the spil l . Personnel should wear suitable
protect ive att ire. The spil l should be contained and neutralized or co ntained and
collected for disposal. After the solut ion is removed, the area where the solut ion
was collected should be thoroughly r insed. The cleanup tools should be rinsed with
a large amount of water and the water discarded down the drain.
To ensure a safe work environment and establish compliance with recommended
limits and guidelines on occupational exposure to germicides, several air sampling
and monitoring techniques can be used. Sampling should be conducted in all areas
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where workers might be exposed to vapor. Monitoring should be conducted during
normal use and whenever there is a major change in protocol, workplace
venti lat ion, case load, or major repair to washers or other automated equipment.
Special attention should be given to periods of time when airborne concentrations
of vapor might be particularly high (e.g., when the worker is pouring the spent
solut ion down the drain or pouring fresh solut ion into a container). Monitoring
should be documented and records maintained.
Exposure can be determined by using a sampling pump to pull a known quantity of
air through a tube containing an absorbent medium. This is analyzed later by
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an industrial laboratory. A passive monitoring badge can be worn by personnel. The
germicide vapor is converted into a s table derivat ive and analyzed.
Monitoring Chemical Disinfection
Standard biological preparations are available only for steri l izat ion processes and
cannot be applied to disinfect ion. The only way to assess the lethality of
disinfect ion is to use the direct-assay steri l i ty test of the f inished product (4). This
test is dif f icul t and t ime consuming, renders the tested object unusable unti l i t is
subsequently recleaned and decontaminated, and is relat ively insensit ive in its
abil i ty to detect low-level contamination.
Because disinfect ion procedures cannot be effect ively monitored biologically, they
must be monitored physically. Records indicat ing exposure t ime, temperature, and
pressure (if applicable) should be maintained.
Agents
No chemical germicide is suitable for all purposes. A number of factors should be
considered in select ing one, including the degree of microbial death needed; the
nature and composit ion of the item being treated; whether the i tem is crit ical,
semicrit ical, or noncrit ical; and the cost, safety, and ease of use. Antiseptics are
not appropriate for disinfect ing inanimate surfaces or objects.
G l u t a r a l d e h y d e
Glutaraldehyde-based solut ions have been widely used because of their excellent
germicidal propert ies, act ivity in the presence of organic matter, noncorrosiveness
with most equipment, and lack of coagulation with proteinaceous material
(3,5 ,8,68 ,70 ,82,83 ,84). Glutaraldehyde has an ex tensive shelf l i fe. I t may be us ed
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as long as 30 days after act ivat ion, provided in-use dilut ion and organic stress are
properly controlled.
Glutaraldehyde is effect ive against bacteria, fungi, and vi ruses at room
temperature. High-level disinfect ion requires 20 to 30 minutes ( 85 ,86,87 ,88 ). I t is
also sporicidal, provided adequate t ime is allotted. Three to 10 hours are required
for steri l izat ion. Elevating the temperature can shorten these t imes (89 ). The
manufacturer's instruct ions should a lways be c onsulted.
Dilut ion often occurs during use, and it is important to ensure that equipment is
disinfected with an acceptable concentration of agent. Glutaraldehyde
concentrat ion test s tr ips that are dipped into the solut ion to determine the act ive
concentrat ion are available. Problems with these str ips have been reported (90). It
is generally recommended that 1% t o 1.5% glutaraldehyde be the minimum
concentrat ion for high-level disinfect ion ( 88). Solut ion concentrat ion should be
monitored at least once every day and a log kept of each test (81).
A wide vari ety of bra nd -name products is av ai la ble . Th ey d if fe r pri ma rily in the
concentrat ion of glutaraldehyde and addit ives. Most aqueous solut ions are acidic
and must be ac t ivated (made alkaline) to become sporicidal (Fig. 34.7). Acid
glutaraldehydes are available and do not require act ivat ion, but some studies have
shown them to have less microbiocidal act ivity than alkaline preparations (88). The
pH needs to be between 7.5 and 8.5 to be sporicidal (5).
View Figure
Figure 34.7Glutaraldehyde. The small container containsthe activator, which must be added to the contents of thelarge container.
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Glutaraldehyde solut ions ev aporate at room temperature. Exposure to
glutaraldehyde can result in a va riety of reactions in health care workers, including
headaches; skin, eye, and mucous membrane irr itat ion; and asthmalike symptoms
(91,92,93,94 ). Salivary gland enlargement attributed to oropharyngeal airways
inadequately r insed after exposure to glutaraldehyde has been reported (95 ). These
symptoms are usually temporary and subside when the individual leaves the area of
exposure but may be exacerbated with repeated contact. If it contacts the eyes,
there may be corneal injury. Unfortunately, so me inst itut ions have used
glutaraldehyde inappropriately to disinfect f loors, walls, and l inen (96).
Ductless fume hoods are av ailable for glutaraldehyde (Fig. 34.6). A neutralizer
should be added to the solut ion when it is t ime for disposal. This wil l el iminate
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the vapors that are c reated when disposing of the solut ion. In some localit ies, i t is
i l legal to put un-neutralized glutaraldehyde into the sewage s ystem.
Glutaraldehyde-neutralizing absorbent mats can be placed under and around baths
and washers to absorb and neutralize spil ls.
O r t h o p h t h a l a l d e h y d e
Orthophthalaldehyde (OPA or Cidex OPA) can achieve high-level disinfect ion at
room temperature after a 12-minute exposure and after a shorter t ime at an
elevated temperature (30,97 ,98 ,99). I t is sporicidal with prolonged exposure (10 0).
I t is often used in an automatic endoscope processing system, which reduces the
processing t ime to 5 minutes (30). I t is noncorrosive. Test str ips to measure the
minimum effect ive c oncentration are available and should be employed prior to
each use. Some localit ies require that OPA be neutralized before disposal.
Neutralizers that change color with deactivat ion are available.
OPA has a number of advantages compared with glutaraldehyde. These include
faster disinfection, minimal odor, no need for activation or mixing, and no OSHA
vapor l imit. I t c an be discarded through the drain. I t is effect ive in the presence of
organic soil. While signif icantly more expensive per gallon than glutaraldehyde, it
may be more economical at high-volume centers (10 1).
While side effects and hazards are l ess with OPA than with glutaraldehyde, eye
contact may cause st inging, excess tearing, and redness. I t stains proteins
(including unprotected skin), and repeated contact may cause dermatit is. Lesions of
the skin, l ips, mouth, and esophagus have been reported following prolonged use of
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a transesophageal echocardiograph probe that may have been improperly
processed with this agent (102 ).
Q u at er n ar y A mm o n i u m C om p o u n d s
Quaternary ammonium compounds (quats) are low-level disinfectants (5). They are
bactericidal, fungicidal, and v irucidal at room temperature within 10 minutes but
have not demonstrated sporicidal effects. I f a spore is coated with a quaternary
ammonium compound, it wil l not develop into a vegetat ive cell as long as the
germicide remains, but if the coating is removed, the spore can germinate. These
compounds are more effect ive against gram-posit ive than gram-negative bacteria.
Quats inactivate the human immunodeficiency v irus (HIV) but some do not
inactivate the hepatit is virus. They are ineffect ive against M. tuberculosis o rhydrophil ic viruses (2,87).
Early generation quats were affected by factors such as hard water, soap, anionic
residues, and proteinaceous soils. They were inactivated by organic materials (e.g.,
cork, cotton, and gauze pads). Some, either used in insuff icient concentrat ions or
in solut ions deteriorated by age or deactivated by the presence of organic soil , not
only fai led to k i l l some microbes but actually supported their growth (8). Newer
ones are mixed with various substances to p roduce synergist ic antimicrobial and
detergent activit ies while maintaining the hard water, protein, and anionic tolerance
necessary in environmental disinfectants. They are quick ac t ing, relat ively nontoxic,
and noncaustic and do not produce noxious fumes. They are useful for c leaning as
well as disinfect ion.
P h e n o l ic C om p o u n d s
Phenolic compounds (phenolics, phenols) are derived from carbolic acid (phenol),
one of the oldest germicides (2,5,8,87 ). They are sometimes combined with
detergents to form detergent germicides. They are good bactericides and a re act ive
against fungi. They are act ive in the presence of organic matter and soap. Phenols
are very s table and remain act ive after mild heating and prolonged drying. When
moisture is applied to a surface that has been previously treated with a phenolic
compound, it can redissolve the chemical so that it again becomes bactericidal.
Phenolics remain act ive in contact with organic soil and for this reason are often
the disinfectants of choice when dealing with gross organic contamination in
general housekeeping.
Most phenolics have a bad odor and are irr i tat ing to skin. They are absorbed by
rubber and may damage the skin or mucous membranes that they contact. They are
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diff icult to r inse from most materials, and residual disinfectant may cause t issue
irr itat ion or hyperbil irubinemia in neonates.
Phenols are considered i ntermediate- to low-level disinfectants. Most phenolic
detergents are tuberculocidal, fungicidal, and bactericidal when used as directed.
Certain viruses, including those associated with widespread common respiratory
il lnesses, are resistant to these compounds. The phenolics are not s poricidal
except at or above 100C. They are used mainly on environmental surfaces and for
noncrit ical devices.
A l c o h o l s
Within health care facil i t ies, alcohol usually refers to either ethyl or isopropyl
alcohol, both of which are water-soluble compounds that are intermediate- or low-level disinfectants (3). The alcohols are best us ed at concentrat ions of 70% to 90%
by volume. Both are effect ive against most viruses, including those for hepatit is B
(HBV) and AIDS (or HIV). The CDC recommends exposure to 70% ethanol for 15
minutes to inactivate HBV, but 1 minute should be adequate for HIV. Alcohols
display high ac t ivity against gram-negative bacteria, fungi, and M. tuberculosis but
cannot inactivate bacterial spores. Isopropyl alcohol cannot ki l l certain hydrophil ic
viruses.
Alcohols hav e a clea ns in g act ion , bu t wi ping a surface wi th an al coho l solu tion ma y
not maintain a 1-minute contact t ime between the surface to be disinfected and the
solut ion (11). They are inactivated by protein but not by soap. I t is not necessary to
rinse items soaked in alcohol, because it evaporates rapidly. For this reason, an
alcohol f lush cycle is used in some automatic processing
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machines. The f lush cycle may be useful to disinfect the channels of f lexible f iber-
optic endoscopes. After high-level disinfection with a chemical germicide and a tap
water r inse, alcohol can remove minor water contaminants. I ts speed of evaporation
promotes rapid drying in the channels. Alcohols are often used to clean the external
surfaces of f iberoptic cables and scopes.
An important us e of a lc oho l is in ha nd rubs (103 ). These reduce the bacteria count
on hands more rapidly than antimicrobial soaps o r detergents. The Associat ion for
Professionals in Infection Control and Epidemiology (APIC) guidelines urge use of
an alcohol-based rub before and after patient contact and after any possible
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contact with body f luids and substances, mucous membranes, broken skin, or
contaminated objects.
Alcohol an d age nts con ta ining alcohol mus t not be a ll owed to ge t into an es thesia
gas sampling l ines, as this can lead to incorrect results when measuring anesthetic
agents (10 4). Alcohols can damage the lens mounts on instruments and tend to
swell and harden rubber and certain plast ics with repeated use (2). Alcohols are
flammable, so care must be taken not to use them in the presence of a heat source
that could ignite the vapor. Alcohol solut ions should be s tored in special f lammable-
materials cabinets (Fig. 34.12).
Io d i n e C omp o u n d s
An iodopho r is a combinati on of iodine and a sol ubil izing agent or carr ier wi th theresult ing complex providing a s ustained-release reservoir of iodine and releasing
free iodine in a queous solut ion (2,3,5,8). Iodophors are bactericidal, virucidal, and
tuberculocidal but may require prolonged contact t ime to ki l l certain fungi and
bacterial spores. Some iodophors do not ki l l M. tuberculosis ( 87 ).
Iodophors a re used principally as antiseptics but are capable of intermediate- and
low-level disinfect ion. Iodophors formulated as antiseptics are not suitable for
disinfect ing medical instruments or environmental surfaces ( 8). Some iodophors are
unstable in the presence of hard water, heat, and organic soil, but most are reliable
general-purpose disinfectants if used in concentrat ions recommended by the
manufacturer. Some metall ic instruments may become corroded if they are routinely
disinfected with iodophors; nonmetall ic items are seldom damaged but may be
stained or discolored.
Per a c et i c A c i d
Peracetic (peroxyacetic) acid is bac tericidal, fungicidal, virucidal, and sporicidal at
low temperatures (3 ,5 ,68 ,105,106,10 7,10 8,109 ,110 ). I t remains effect ive in the
presence of organic material. I t may be effect ive against prions (111). An important
advantage is that its decomposit ion products (acetic acid, water, oxygen, and
hydrogen peroxide) are not harmful. I t ca n corrode copper, brass, bronze, plain
steel, and galvanized iron, but these effects can be reduced by addit ives and pH
modif icat ions (88 ). A concentrated solut ion can cause eye and skin damage, but i t
has no OSHA exposure l imit.
Steris 20 is a patented product that has been developed specif ically for Steris
processors. The act ive ingredient is a concentrate of 35% peracetic acid plus
corrosion and degradation inhibitors that are contained in a sealed, single-use
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container. I t should be used only i n a Steris processing system. I t is not intended
for open-pan techniques.
A Ste ri s sys tem is sho wn in Figure 34.8. Equipment to be steri l ized must be c lean
but need not be dry. The equipment is placed in a special tray, which is then
P.972
placed in the processor. The steri l izer has a variety of trays, containers, and
adaptors to accommodate various medical devices. Each tray has holes for f luid
entry and drainage and is designed so that there is a continuous f low of steri lant on
exposed surfaces and through internal channels of i nstruments.
View Figure
Figure 34.8The Steris system A:Items to be sterilized arecleaned, then placed in a tray. The tray is then placed in the
sterilizer. B:After the lid is closed and the processing cycleis started, the processor automatically opens the sterilant
concentrate and mixes it with filtered water. The usedilution of the sterilant enters the tray, covering the
instruments, and is circulated for 12 minutes. It is thendrained from the chamber, and the chamber and tray are
rinsed four times with sterile water. Next, sterile air ispumped into the chamber to displace the rinse water. A
printout is provided, confirming that the sterilizationparameters were met.
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View Figure
Figure 34.9The sealed package of sterilant is placed in theprocessor, and the lid is punctured before the lid is closed.
Af ter the tra y is pos iti on ed in the Ste ris proc essor, a seal ed package of s te ri la nt
concentrate is placed in the steri l izer (Fig. 34.9). The l id is closed and the
processing cycle started. During the cycle, the l id is sealed. The processor
automatically opens the steri lant concentrate and mixes it with a controlled volume
of filtered sterile water heated to between 50C and 56C. The diluted sterilant
enters the tray, covering the instruments, and is ci rculated for 12 minutes. I t is then
drained from the chamber, and the instruments and chamber are rinsed four times
with steri le water. Then, steri le air i s pumped into the chamber to displace the rinse
water. The cycle takes from 20 to 45 minutes, depending on the init ial temperature
of the water and how extensively the local water supply must be f i l tered. After the
cycle is complete, the unit f lushes the diluted steri lant and rinse water direct ly into
a drain. The tray can be transported direct ly to a s teri le f ield.
The Steris processor monitors and maintains the parameters necessary to ensure
steri le processing. I t wil l stop the cycle if a process error is detected. At the end of
each cycle, a p rintout confirming that the steri l izat ion parameters were met is
provided. Spore str ips can be used as biological monitors. These go through the
steri l izer and are then retrieved for culturing.
The Steris system provides a quick method of dis infect ing a wide variety of heat-
sensit ive immersible instruments, including f iberscopes (112,11 3) (Fig. 34.10). The
Steris system has been found to be effect ive in s teri l izing the lumens of
endoscopes when organic soil and salt were present (114).
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View Figure
Figure 34.10Endoscope in Steris processor. Note thetubings that are connected to the channels.
The Steris system is less damaging to delicate instruments than steam steri l izat ion
and is compatible with a wide variety of materials, including plast ics, rubber, and
most heat-sensitive items. It is important that the absence of long-term effects on
the devices being steri l ized by the Steris system are confirmed with the instrument
manufacturer. Polymers, glasses, coatings, adhesives, and sealants that are
typically used in medical devices are compatible with the p rocess. Untreated metals
such as copper, brass, si lver, aluminum, and iron are subject to oxidation.
Alum inum anod ize d coa t ing can bec ome du ll .
The Steris system is especially useful f or items requiring a quick turnaround t ime. I t
is faster than s teri l izat ion with EO or glutaraldehyde and can be used on wet or dry
items. No steri lant dilut ion is necessary, and personnel are not exposed to a ny
toxic chemicals. Consequently, i t can be located in the operating room suite. The
site requirements are a tap water supply, a drain, and electricity. I t l eaves no
residue. Wrapping is not necessary.
This system does have s ome disadvantages. Unlike some automated processors,
the Steris machine has no cleaning cycle. Costs per cycle are greater than if
glutaraldehyde is used (11 5). Only i tems that c an be totally immersed can be
steri l ized, and only a small number of instruments can be processed in a cycle. The
trays cannot be used for extended storage, so processing must be consistent with
just-in-t ime delivery.
Ch l o r i n e C omp o u n d s
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Several chlorine compounds are available for use as disinfectants, including
sodium and calcium hypochlorite (household bleach), chlorine dioxide, and
chloramine T (3,5,11 6). The hypochlorites are
P.973
the most widely used. They are inexpensive and fast act ing. They are available in
both l iquid (sodium hypochlorite) and solid (calcium hypochlorite) form. Relat ively
low concentrat ions of sodium hypochlorite (50 ppm) exhibit rapid act ivity against
vegetat ive bacteria. One hundred ppm is effect ive against most fungi. Many vi ruses
are inactivated at concentrat ions of 200 ppm, with HIV being susceptible at
concentrat ions as low as 50 ppm. HBV exhibits marked inactivat ion at 500 ppm.
Concentrat ions of 1,000 ppm are considered adequate to achieve high-level
disinfect ion. A 1:5 to 1:10 di lut ion wil l destroy the agent of Creutzfeldt-Jakob
disease (CJD) after an exposure time of 1 hour (11 7).
TABLE 34.2 Preparation of Household Bleach for Disinfectionaa
Desir ed Chlor ine Concentration 5,000 ppm1,000 ppm 500 ppm 100 ppm
Dilution for use within 24 hours 1:10 1:50 1:100 1:500
Dilution for use for 1 to 30 days 1:5 1:25 1:50 1:250
aStarting with 5.25% NaOCl, which contains 50,000 ppm of free chlorine.
Table 34.2shows the dilut ion of 5.25% NaOCl (household bleach) needed to
achieve the desired chlorine concentrat ion. Solut ions that wil l b e used for extended
periods (1 to 30 days) should have an init ial concentrat ion twice as high as actually
desired and should be stored in an opaque container.
Chlorine solut ions are not often used for instrument disinfect ion but have been
used widely in environmental disinfection. Current OSHA regulations consider
dilut ions of 1:10 to 1:100 chlorine to be acceptable for use with b lood spil ls. Other
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uses include spot disinfect ion of countertops and f loors and decontamination of
resuscitat ion manikins.
Highchlorine compound concentrat ions are corrosive as well as irr i tat ing to
personnel, and their use should be l imited to si tuat ions in which there are unusually
high concentrat ions of microorganisms (8). Their use is l imited by their
corrosiveness, inact ivat ion by organic matter, and relat ive instabil i ty. They may
leave a residue and are irr i tat ing to the skin, eyes, and respiratory tract.
Chlorine dioxide is used in a gaseous phase (11 8). I t is not stored but is generated
at the point of use. Advantages are that it leaves l i t t le residue and is nonozone
deplet ing. Disadvantages involve material incompatibil i ty.
Hy d r o g e n P er o x i d eHydrogen peroxide is an effect ive bactericide, fungicide, virucide, and s poricide
(2,3 ,5,11 9,120). I t is commercially available in sev eral dif ferent concentrat ions. I t is
not inact ivated by organic matter. There are no restrict ions on disposal. I t rapidly
loses effect iveness when exposed to heat and l ight and requires careful s torage. I t
can damage rubber and plast ic and may corrode copper, zinc, and brass. I t is an
irr itant to the skin and eyes. A 7.5% solut ion achieves high-level disinfect ion in 30
minutes. An effect ive low-level disinfectant, 3% hydrogen peroxide is useful for
work surfaces. Hydrogen peroxide is used for plasma sterilization (see below).
Ozo n e
Ozone steri l izers use oxygen, water, and electricity to produce ozone
(121 ,122,123). The gas is humidif ied and dispersed into a steri l izat ion chamber. A
steri l izat ion cycle includes three stages: air evacuation, fol lowed by air and ozone
mixture admission; an exposure stage; and a stage of v acuum-drying and ozone
removal. After the cycle, the ozone passes through a catalyt ic converter that
changes it back to ox ygen.
Ozone steri l izat ion is good for most goods that need low-temperature steri l izat ion.
It is not approved for f lexible scopes and reactive metals such as copper and brass.
It is compatible with most anodized aluminum steri l izat ion containers and all plast ic
containers. I t is unsuitable for devices that contain natural gum rubber products,
some plast ics, and some metals such as brass and copper.
Accordin g to the ma nu fac tu rer, ozo ne can steri l ize s in gle s tai nl es s s te el lumens
with an inside diameter of 2 mm and no longer than 250 mm, lumens with an inside
diameter of 3 mm or larger and no longer than 470 mm, and those with an inside
diameter of 4 mm and no longer than 600 mm (121,122 ).
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The process is environmentally fr iendly and produces no toxic residuals. I t requires
no vent or drain and uses only oxygen, electricity, and a l i t t le water. The steri l izer
can be transported easily. No exhaust gas venti lat ion duct is required in a room
that is adequately venti lated. The treated objects are dry. No rinsing or degassing
is required. While signif icantly slower than gas plasma, this process is less
expensive.
F o rma l d e h y d e
Formaldehyde is a highly toxic and f lammable gas that has been used as a
disinfectant and a steri lant in both a water-based solut ion (formalin) and the
gaseous state (5). I t is noncorrosive and is not inact ivated by organic matter.
P.974
Al though formali n is a high -lev el dis in fe cta nt , i ts uses are l im ite d by its pu ng en t
odor and fumes, which irr i tate the skin, eyes, and respiratory tract. I ts toxicity
requires that disinfected materials be thoroughly rinsed before use. NIOSH has
indicated that formaldehyde should be handled as a potent sensit izer and probable
carcinogen. Kits are available to absorb and neutralize formaldehyde spil ls.
Steri l izat ion with low-temperature steam and formaldehyde is used in some
countries (5 ,124).
Advantages and Disadvantages of Chemical Disinfection
and Sterilization
Adv an ta ges of l iquid chem ic al disinf ec ti on inc lu de econom y, speed, and simpl ic ity.
This is es pecially important in busy endoscopy suites because it enables equipment
to be used several t imes a day. I t is useful for equipment that does not require
steri l izat ion but does require high-level disinfect ion.
Chemical disinfect ion cannot be used for all types of equipment. Many devicescannot be soaked. Prepackaging is not possible, and the equipment wil l be wet.
There is a r isk of recontamination during subsequent r insing, drying, or wrapping.
With most agents, steri l i ty cannot be guaranteed. I t is more expensive, less
effective, and more prone to human error than steam sterilization. Hinged
instruments must be opened and those with sl iding or mult iple parts disassembled.
Some solut ions are irr i tat ing to t issues and have unpleasant odors. Personnel who
handle them must take precautions to avoid prolonged skin contact or vapor
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inhalat ion (92 ). The chemicals may be absorbed onto the treated items, causing
harm to the patient.
A sign if icant di sadvan tage of cold s te ri l izati on is the lack of a good method for
validat ion. The eff icacy can be monitored only indirect ly, through surveying patient
outcomes, to identify s ubsequent infect ions that can be attr ibuted to exposure to
the reusable device (125 ). Most health care inst itut ions have an act ive surveil lance
program in which infect ion control pract it ioners seek to identify nosocomial
infect ions.
Gas St e r i l i z a t i o n
Characteristics of Ethylene Oxide
Ethylene oxide (EtO, EO) is a colorless, poisonous gas with a sweet odor
(126 ,127,128,129 ,130,13 1,132 ,133 ,134). I t is available in high-pressure tanks and
unit-dose ampules and cartr idges. I t is f lammable in concentrat ions of 3% or
greater. Manufacturers have dealt with this hazard in two ways. EO may be mixed
with carbon dioxide or hydrochlorof luorocarbons (HCFs). Mixtures containing up to
12% EO in these inert di luents are nonflammable but retain their steri l izing abil i ty.
A mix ture of EO and chlo ro f lu oro carbo n (CFC ) was us ed in the pas t, but the us e of
CFCs was banned because of damage to the ozone layer. HCFs are s imilar to CFCs
but are less damaging to the ozone layer (127,13 5). Their use wil l be eliminated in
the United States by 2030.
EO is supplied mostly as 100% in small c ylinders, cartr idges (Fig. 34.11), or
ampules. Equipment is designed for gas containment and to minimize the risk of
f ire or explosion (12 6,127,13 6). A cartr idge is punctured only after it is secured in a
sealed and locked steri l izat ion chamber. An ampule is broken only after it is placed
in a bag with the medical device to be steri l ized. Explosion-proof cabinets should
be used for storing cartr idges of 100% EO (Fig. 34.12).
EO kil ls bacteria, spores, fungi, and v iruses. I t penetrates into crevices and through
permeable bags. I t is not degraded by organic soil but wil l not penetrate dried
protein material.
Preparation for Ethylene Oxide Sterilization
I t is important to verify that a device is suitable for steri l izat ion using EO. The
manufacturer's instruct ions should be c onsulted. Some devices need to be
steri l ized at a lower temperature.
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Before packaging, items must b e disassembled, cleaned, dried, and wrapped.
Disassembly is important to remove barriers to free movement of gas. Caps, plugs,
valves, and/or stylets must be removed. Hollow-bore
P.975
products such as needles and tubes must be open at both ends. The wrapping must
be permeable to EO gas and water vapor and allow proper aeration ( 13 7).
View Figure
Figure 34.11Cartridge of EO. The cartridge is puncturedonly after the sterilizer door is closed and locked and properconditions are met. There are no external tanks, hoses, or
gas source hookups, which are major sources of potentialoperator exposure to EO.
View Figure
Figure 34.12Explosion-proof cabinet for flammablematerials.
Blood and other proteinaceous materials can act as a barrier to EO. I f salt and
protein are present in a narrow lumen, steri l izat ion wil l not be achieved consistently
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(114 ). Therefore, equipment must be thoroughly cleansed and rinsed before
steri l izat ion.
Items for gas steri l izat ion must be free of water droplets. They should be allowed to
dry in ambient air or towel dried. The use of h eated air should be avoided because
EO steri l izat ion depends on the presence of adequate (but not excessive) moisture.
A re lat ive humidity between 35% and 70% an d a te mpera ture be tween 18C and
22C throughout the processing and s torage facil i ty are recommended (23 ,128).
Devices should be s orted according to the steri l izat ion t ime and recommended
temperature. I tems to b e steri l ized are placed in wire baskets, metal steri l izer carts,
or other carriers that do not absorb EO. The steri l izer manufacturer's instruct ions
for loading should be carefully fol lowed. I tems should be loaded loosely to allow
gas to penetrate throughout the load. I tems should be loaded in such a fashion that
packages will not contact the chamber walls or the operator's hands when the load
is transferred to the aerator. Some instruments are steri l ized in r igid containers that
have f i l ters on the l id and bottom to allow dif fusion of steri lant gas. There may also
be an addit ional l id attached to the upper l id.
The Sterilization Process
P r o c e s s i n g P a r am e t er s a f f e c t i n g E t h y l e n e O x i d e
S t e r i l i z a t i o n
Gas Concentration
As th e EO concentr at io n inc reases at a g iv en temp era tu re an d rel ati ve hu mi di ty,
the microbial inact ivat ion rate increases up to a certain range when it begins to
plateau (12 6). EO concentrat ions between 450 and 750 mg/L are commonly used in
processing medical products. The solubil i ty of EO in the product and the dif fusion
rate through the product wil l inf luence the steri lant concentrat ion. The operating
pressure of the EO cycle wil l greatly inf luence the gas dif fusion rate. Packaging
may also be cri t ical. Devices that perform continuous EO monitoring in the
steri l izat ion chamber are av ailable.
Temperature
Increasing the temperature can decrease the necessary exposure time. Many
steri l izers provide a select ion of temperatures. In health care, processing cycles
are commonly performed between 38C and 60C. Some conduct sterilization at
room temperature. This is equally eff icacious if other factors (exposure t ime and
concentrat ion) are adjusted.
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Relative Humidity
Moisture hydrates microbes, making them more susceptible to destruct ion by EO.
Therefore, humidity must be controlled in the storage and cleaning/processing area
and in the steri l izer itself . Most EO chambers are held between 40% and 80%
relat ive humidity. Desired humidity levels are usually accomplished by low-
temperature steam inject ion. For tabletop monitors, i t is necessary to add water to
the steri l izer.
Exposure Time
The necessary steri l izat ion t ime wil l depend on the factors mentioned previously.
The t ime generally ranges between 1.5 and 6 hours in automatic steri l izers. Up to
12 hours may be required.
S t e r i l i z e r s
EO steri l izers range in s ize from small tabletop to large f loor-loading models (126 ).
The basic design includes a p ressure-rated vessel with a p ort for admitt ing air, a
vacuum pump to evacuate the chamber gas contents, a jacket to heat the vessel, a
steam source to humidify the chamber and its contents, and a means to inject the
sterilant. A recent change has been to integrate computers, microprocessors, and
software into the control, monitoring, and documentation of s teri l izat ion processing.
Anc il lary equipm en t such as recirc ul ati on blowe rs to equ il ibrate the chamber
environment, exhaust systems to minimize release of steri lant into the work
environment on door opening, an