camfil farr - appendix j technical-bulletin

7/28/2019 Camfil Farr - Appendix J Technical-Bulletin

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Thefilter shall have a Minimum Efficiency Reporting Value Thefilter shall have a Minimum Ef ficiency Reporting Valueofof MERV (X) when evaluated under the guidelines ofMERV (X) when evaluated under the guidelines of ASHRAE Standard 52.2-2007. It shall also have a MERV-AASHRAE Standard 52.2-2007. It shall also have a MERV-Aof (XA) when tested per Appendix J of the same standard.of (XA) when tested per Appendix J of the same standard.

(X - Substitute required value per application recommendations)(X - Substitute required value per application recommendations)

TECHNICALBULLETINASHRAE 52.2Appendix J

High efficiency air filters are usedto remove sub-micron particlesincluding contaminants such asbacteria, fungi, manmade particlesuch as dust and fibers, and morecritical airborne infectious agentstransferred from person to personsuch as rhinovirus (common cold)and flu. They also remove dropletnuclei, produced through sneezing,coughs and conversation whichcarry various infectious agents fromperson to person.

Critical Particle Sizes

Sub-micron particles are themost critical size of considerationbecause 99% of all airborneparticles are under 1-micronin size. They are capable ofpenetrating deep into thehuman lung. Larger particles aretypically removed from the airby prefilters or gravitational andother natural forces. The humanbody’s respiratory system hasmechanisms in place that removethese larger particles before theyenter the alveoli of the lungs wherethey cause the most damage.

Particle Capture Mechanisms

Air filter manufacturers usedifferent particle capturetechnologies to provide cleanair. For commercial filters, theprimary capture mechanisms aremechanical and electrostatic.

In 1999, ASHRAE introducedStandard 52.2, Method of Testing

General Ventilation Air- Cleaning Devices for Removal Ef ficiency by Particle Size. MERV, or minimumefficiency reporting value, wasestablished to allow users a way toevaluate one filter versus another.

The higher the MERV, the moreefficient the air filter. Users couldalso evaluate a filter’s effectivenessin removing contaminants byparticle size, either through thebroad spectrum of the singlenumber MERV or by reviewingthe complete particle-size-versus-efficiency curves that are a part ofthe standards reporting process.

Other design handbooks andstandard materials for HVACsystem design adjusted their filterefficiency recommendations basedupon their specific contaminantsof concern, and recommendedthe proper MERV filtration. Asan example, all cognizant designauthorities recommend MERV 14for the final filter in medical facilityHVAC systems. A MERV 14 filterhas an efficiency of 48% at 0.3

micron particle size. The standardfilter selection for office buildings isa MERV 13, which has an efficiencyof 31% at 0.3 micron particle size.Both of these filters have excellentsub-micron particle captureefficiency.Fine fibers (left), manufactured from micro glass, capture particles through

diffusion and interception. Sub-micron particles are held in place by Van De Waalsforce. Ef ficiency is consistent throughout the life of the filter. The coase fibers of electret media (right) require a charge to attract and holdparticles. Once the fibers become insulated with contamiinant, or lose their charge,thefilter ef ficiency drops. Filter fiber size is always an ef ficiency consideration.



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Fine Fiber Mechanical Filtration

Mechanical filters use straining,diffusion and interception andhave removal efficiencies up to98% on particles 0.3 micronin size (one three-hundredththe diameter of a humanhair). Mechanical filters willalso maintain their publishedefficiency over time. A filterthat has an initial efficiency ofMERV 13 will maintain MERV 13efficiency throughout the life ofthe filter.

When considering high efficiencymechanical filters (MERV 11 toMERV 16), the primary principles

of particle removal for 1-micronand smaller are diffusion andinterception. These principlesrequire the application of finemedia fibers, 0.6 to 2 micronin size, to attract and hold sub-micron particles. The higher theefficiency of the filter for sub-micron particles, the smaller thediameter of the filter fiber. Smallerfibers, such as microfine glass, aremore difficult to produce from thenatural materials used for fine fiberair filters, so manufacturing costsincrease alongside the cost of thefilter.

Coarse Fiber Electret Filtration

Coarse fiber filters incorporatemechanical principles and alsouse an electrostatic charge toenhance particle capture efficiencyto obtain a MERV of 11-15 whentested per ASHRAE Standard 52.2.Coarse fibers are much larger, inthe 2 to 20 micron range, so thefilter fiber’s size in relationshipto sub-micron particles, limitsits mechanical ability to capturethese contaminants. The primarymechanical principle used isstraning. This principle removeslarger particles from the airstream.

Media manufacturers impart acharge on the media, or design themedia so that a charge is inducedthrough airflow friction. Thisincreases the filter’s efficiency inthe sub-micron particle range usingthe capture force of electrostaticattraction.

It also produces the desired MERV,at least temporaily, when tested

per ASHRAE Standard 52.2. Thislarger media fiber size costs lessto manufacture than fine fibermedia and is the primary drivingforce behind air filter manufacturerofferings.

Independent research by cognizantauthorities and doctoral programshave looked at the performanceof coarse fiber filter products(electrostatic) over time and haveconcluded that these products

experience a drop in efficiency asthe filters load with particulate, oras the charge naturally dissipates.A coarse fiber filter may operate ata MERV 13 at installation and maydecrease in efficiency to a MERV9 over a relatively short period oftime.

Development of Appendix J

The ASHRAE 52.2 StandardCommittee has beendebating the issue of filtersthat drop in efficiencysince the first version ofthe Standard in 1999. TheStandard Committee iscomprised of a congressof filter and filter mediamanufacturers who wereunable to develop aconsensus of how to bestaddress this problem inthe body of the Standard.The division was clearlyalong the lines of each

manufacturer’s interests.Although Committeequorums were in favor

of addressing the issue in theStandard, full consensus ispreferred and agreement could notbe reached.

An alternative solution suggestedplacing an optional test methodoutside the body of the Standardas an Appendix. In that manner,manufacturers and users who want

confirmed assurance that theirfilters will perform as expectedthrough their entire life in thesystem would have an authority-defined method of determiningwhether a specific filter woulddrop in efficiency. Defined as a‘conditioning step’, the procedurewas included with Standard 52.2 asan informative appendix.

Appendix J is titled Optional Methodof Conditioning a Filter Using FineKCL Particles to DemonstrateEf ficiency Loss That Might beRealized in Field Applications. TheCommittee incorporated ASHRAE-funded research, independentpapers and the knowledge frommembers of the Committee toauthor the Appendix.

TECHNICAL BULLETIN

ASHRAE 52.2 - Appendix J

All Camfil Farr 5-Star products incorporate fine fibertechnology to ensure that those products maintain theirpublished efficiency throughout the life of the filter. Our

R&D department reviewsfiber size and evaluates mediaalternatives on a continous performance assurance program.



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Appendix J Testing Aerosol

The most critical component of theprocedure was the selection of theaerosol to simulate field loading ofa filter. Potassium chloride aerosol(KCl) was selected to reproducethe fall-off in efficiency that electretfilters may experience in real-lifeapplication. The selection wasbased upon extensive research andwithin the Appendix, the Committeestates “The ‘conditioning step’described herein is representativeof the best available knowledgeof real-life filter efficiencydegradation at the time of thepublication of this procedure.”

The procedure spans eight pagesand mirrors most of the proceduresprescribed in the Standard, with theexception of a ‘conditioning step’where the KCl is aerosolized usinga strict protocol and introduced tothe filter in a standard ASHRAE testduct.

Particle counts are taken upstreamand downstream of the test filter,with the ‘conditioning step’being repeated until the filter

shows no further signs ofsignificant drop in efficiencyor the filter reaches finalresistance because of dustloading. The correspondingparticle ranges for the‘conditioning step’ are thesame as the particle rangeslisted in the main body ofthe Standard and the samemathematics are applied toobtain a value defined asMERV-A.

Recommendation

Camfil Farr recommendsthat all filter users requestthis optional testing stepto ensure that they arereceiving the particleremoval efficiency they areexpecting throughout the

life of the filter. Use the followingstatement in a request for a quoteor new construction specificationto ensure the efficiency of particleremoval required:

The filter shall have a MinimumEfficiency Reporting Value of MERV(X) when evaluated under theguidelines of ASHRAE Standard52.2-2007. It shall also have aMERV-A of (XA) when tested perAppendix J of the same standard.(X - Substitute required value perapplication recommendations).

Industry statements

Every air filter probably has anapplication wherein it may excel,but some salespeople may makestatements that are misleading orconfusing in their zeal to promotetheir products.

Camfil Farr has summarized someof these statements and providedadditional points of condideration.Please contact Camfil Farr withyour specific concerns if they arenot addressed herein.

Electrostatic filters will drop inef ficiency and as the dirt loads, thedirt becomes part of the filter andthe filter ef ficiency increases.

The statement is misleadingat best. As filters load withcontaminant, the capturedcontaminant becomes part ofthe filter and the dirt acts as astraining mechanism to removelarger particles. Studies show thatthe filters do not increase or re-gain efficiency in the critical sub-micron particle size range whichconstitutes 99% of all airborneparticles.

Coarse fiber air filters have a lower

resistance to air flow than fine fiber filters.

Sometimes true. But not aconsistent statement whenconsidering that coarse fiber filterstypically rise in pressure drop fasterthan do fine fiber filters.

Filter pressure drop involves manyfactors; the two most critical factorsare amount of media area and filter

configuration. There isa wide variance across

all available filters andone manufacturer mayhave a lower resistanceto airflow than another,whether they are usingcoarse or fine fibers toobtain the same MERV.

Literature, withsupporting test reports,from the manufacturershould always bereviewed to ensure the

best value.There are studies thatshow that a coarsefiber filter increases inresistance to airflowfaster than a fine fiberproduct, but that is onlytrue of some products,not all.

TECHNICAL BULLETIN


With multiple air filter testing laboratories around the world, CamfilFarr evaluates our products and competitive products on a daily basis. Tests are performed on virtually every type of air filter, from low-levelarrestance type HVAC gradefilters to the ULPA filters used in thehighest level of cleanrooms. Flat sheet testing and discharge, dustcollection cartridges and media, and carbon products may be evaluatedin other Camfil Farr testing rigs.



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TECHNICAL BULLETIN


References

ASHRAE Standard 52.2, Method of

Testing General Ventilation Air-Cleaning

Devices for Removal Ef ficiency by

Particle Size

ASHRAE Test Guide, Camfil Farr

The best avenue for users todetermine the best value is to seeklife-cycle cost data based uponactual filter installations.

Fine fiber filters shed and coarsefibers do not, thus fine fibers create ahealth hazard.

Studies have shown that bothtypes of filters shed, but this isprimarily during the initial days ofinstallation as the filter clears itselfof manufacturing dusts.

Certain manufacturers have raisedconcern that the glass fibersof the fine fiber media may becarcinogenic. This was based on

a single study over 20-years agowhere glass fibers were implantedinto a rat and the rat developedcancer. The amount of fibers thatwas implanted was the equivalentof implanting a basketball into ahuman being. Also, airborne fibersare not implanted; they are inhaledand typically removed by thebody’s natural protection systems.

Also, glass fibers have proven tobe soluble, again, by the body’snormal means of protection.

As a result of that single study,glass has been one of the moststudied items in relation to itssafety than virtually any otherproduct. Not one study hasreached the conclusion that glass isa carcinogen. The same may not beclaimed for the coarse or syntheticfibers used in electret media filters,not even the solubility of the fibercomponents.

The test does not have repeatability

from one testing laboratory toanother test laboratory.

At least eight manufacturers orregional location laboratories wereround-robin tested to ensure therepeatability of the procedure.

One laboratory showed inconsistent

results in relation to the results atthe other facilities. Upon committeemember review, there wereinconsistent design discrepanciesat the non-conforming facility when

compared to the other laboratories.

Additional concerns have beenvoiced with regard to environmentalconditions. Environmentalconditions were eliminated as aconcern because testing mustnow be done within controlledtemperature and humidity ranges.

There would be a cost or costsassociated with manufacturers being required to perform this optional test.

Airfi

lter manufacturers have onething to sell: clean air. Reputablemanufacturers have testinglaboratories to ensure theirproducts perform as advertised,and most manufacturers also haveASHRAE 52.2 test ducts.

The expense to thesemanufacturers is minimal becausethe optional testing requirestime, not more equipment. TheAppendix J option uses the sameequipment as the standard MERV

test. Camfil Farr has tested everyone of our products, and most ofour competitors’ filters, for MERV-Aperformance.

Some of our laboratories run24-hours per day. We consider it asmall expense to provide what theend user requires: clean air.

The only proof to ensureperformance is testing per both thestandard and optional appendix.

It has also been stated thatsome products would requirere-design or modification; this isonly an expense if the filter is notperforming to published values inthe first place.

Statements about literature

changes or updates as an expense;hardly a factor in today’s digitaldocument producing world.

The true expense is poor filterperformance in a user’s applicationwhere they are expecting astandard of performance andproduct manufacturing care.

As an Appendix, the MERV-A optionhas not been subject to peer review.

In order to obtain AmericanNational Standards Institute(ANSI) status, a document has tobe presented to industry expertsfor peer review. Most, if not all ofthose experts are on the ASHRAE

Committee that developed theAppendix.

Peer review is an ANSI processthat was introduced to ASHRAEdocuments in the late 90’s toconsolidate efforts in cross-overstandard writing organizations.

Only items that are within thestandard body itself are subject tothe peer review process. The mostimportant reviewer of this processat this point is the end user.

After inspection of the text andlogic, we find most users areaccepting the option and requiringit in their request for quotes andin specifications for their newconstruction projects.

camfil farr - appendix j technical-bulletin

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