1 3MJobHealthHighlights Vol.�5.No.4 June�007

JobHealth HighlightsTechnical Information for Occupational Health and Safety Professionals

IntroductionOn August 24, 2006, the Occupational Safety and Health Administration (OSHA)

completed the revision of its respiratory protection regulation, 29 CFR 1910.134,

by issuing a fi nal rule specifying respirator Assigned Protection Factors (APFs).1

The APF values and their use were the subject of an earlier 3M publication.2 In

the preamble to the fi nal rule, OSHA describes its reasoning for setting each of

the APFs. This article will focus on the two APF values that were most discussed

during the rulemaking: the APF of 10 for all half facepieces, and the “qualifi ed”

APF of 1000 for hoods and helmets.

DiscussionWhen OSHA proposes any regulation, it is bound by law to use “. . . the latest

scientifi c data in the fi eld” and “(w)henever practicable, the standard promulgated

shall be expressed in terms of objective criteria and of the performance desired.”3

This is exactly what OSHA did in developing the APF table. The rulemaking was

based on a comprehensive review of the available literature and data on respirator

performance. Careful consideration was given to data generated in simulated

workplace protection factor (SWPF) and particularly, workplace protection factor

(WPF) studies. Both types of study simultaneously measure the concentration

of an air contaminant outside and inside respirators worn by people performing

either simulated or actual work activities. SWPF studies use artifi cially generated

contaminants and are done under carefully controlled laboratory conditions. WPF

studies are performed in real workplaces, using contaminants generated by the

work process, i.e., the contaminants for which the respirators are selected to provide

protection.

ASSIGNEDPROTECTIONFACTORS:KEYELEMENTSOFTHEFINALRULE

Figure1.Aloosefittingfacepiecewithheadprotection.

LarryJanssen,C.I.H.LarryJanssenisaCertifiedIndustrialHygienistwiththe3MOH&ESDLaboratory.

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� 3MJobHealthHighlights Vol.�5No.4 June�007

Figure�.Ahelmet-stylerespiratoryinletcoveringwithaweldingvisor.

Half Facepiece RespiratorsFor half facepiece respirators, OSHA concluded that WPF data “. . . is a better

measure of the protection provided by half mask respirators than data collected

only from SWPF studies or other highly controlled studies.”1 The half facepiece

WPF database OSHA analyzed ultimately consisted of 1339 data points. Data from

elastomeric and filtering facepiece respirators were examined separately. In addition

to OSHA’s own analysis, four statisticians were consulted to analyze the data to

determine the level of protection provided by each type of half facepiece respirator.

The data were also carefully evaluated to determine if both types of half facepieces

should be given an assigned the protection factor of 10, which OSHA had proposed.4

The result of OSHA’s analysis is shown in Table I.

Elastomeric Half Facepieces Filtering Facepieces

Number of Data Points 579 760

Percentage of WPFs less than 10 4.5 1.6

5th percentile WPF 1� 18

TableI.SummaryofAnalysisofWPFDataforHalfFacepieces

OSHA chose the lower 5th percentile point estimate of the WPF distribution to

establish APFs. This value represents the level of protection that 95% of respirator

users are expected to exceed. Conversely, 5% of WPFs are expected to be lower

than the 5th percentile estimate. As shown in Table I, the WPF data OSHA

analyzed agree well with this expectation. From the extensive data analyses, OSHA

concluded that an APF of 10 was appropriate for both elastomeric and filtering half

facepiece respirators.

It is also important to note that while substantial data were presented and analyzed

to support the APF of 10 for all half facepieces, no data were presented to suggest

the APF for either elastomeric or filtering half facepieces should be a value other

than 10. For instance, while some participants in the rulemaking argued for an APF

of 5 for filtering facepieces, their arguments were based on assumptions or opinions

rather than objective data. OSHA made numerous requests for supporting data

during the entire rulemaking, but none were provided. OSHA’s comment regarding

criticism of its own data analysis illustrates this point: “In all cases, concerns raised

by commenters about the composition of the dataset used in the metaanalysis, or the

statistical methods used to conduct the analyses, were unsubstantiated by evidence

submitted to the record despite repeated requests by OSHA for either specific

examples or additional evidence.”1 Thus, OSHA’s decision to use an APF of 10 for

all half facepieces fulfills its legal obligation as well as being the only technically

defensible decision it could make.

WPFdatawasgivenprecedenceoverSWPFdata.

3 3MJobHealthHighlights Vol.�5.No.4 June�007

Hoods and HelmetsOSHA proposed a “qualifi ed” APF of 1000 for hood and helmet powered air

purifying respirators (PAPR) and supplied air respirators (SAR).4 That is, OSHA

included an alternative APF of 25 for hoods and helmets unless it could be shown

that a particular device maintained positive pressure during use. There are

basically two reasons that OSHA included this caveat:

1) The National Institute for Occupational Safety and Health (NIOSH) had

recommended an APF of 25 for hoods and helmets since 1987.5 It is interesting to

note that 25 was based on WPF studies of PAPR with loose-fi tting facepieces, which

have been recognized as a different type of respiratory inlet covering for many

years6 (see Figures 1 and 2).

2) While several WPF studies and one SWPF study7 of PAPR and SAR indicated

the APF of 1000 was appropriate, the SWPF study also reported on one hooded

SAR whose performance was far less than a SWPF of 1000.

OSHA believed that maintenance of positive pressure inside the hood or helmet

during use would assure adequate protection.

A number of problems with the “positive pressure” criterion were presented during

the subsequent stages of the rulemaking. For example, OSHA did not specify a

test procedure to determine compliance with the criterion. That lacking, the test

conditions could have been selected such that all devices would pass or all devices

would fail. In either case, the test results would have been meaningless. Secondly,

all the devices that were shown to perform very well in the SWPF study OSHA cited

as the basis for the APF of 10007 had two or more negative pressure occurrences

during their testing. This indicates that maintenance of positive pressure is not the

only factor that determines the protection a device will provide.

For these reasons, OSHA maintained the dual APFs of 1000 or 25 for hoods and

helmets but changed the criterion for “earning” the APF of 1000. The caveat now

reads: “The employer must have evidence provided by the respirator manufacturer

that testing of these respirators demonstrates performance at a level of protection of

1000 or greater to receive an APF of 1000. This level of performance

can best be demonstrated by performing a WPF or SWPF study or

equivalent testing. Absent such testing, all other PAPRs and SARs

with helmets/hoods are to be treated as loose-fi tting facepiece

respirators, and receive an APF of 25.”

The revised caveat is much more reasonable than was proposed,

because it is based on the measured performance of each device.

However, it is still vague in that, as OSHA acknowledged, SWPF

and WPF yield different performance values and must be interpreted

differently. In addition, it is not known what test results might be

the protection

positive pressureMaintenance of

is not the only factorthat determines

a device will provide

Pleaserecycle.©3M�007.Allrightsreserved.

Occupational Health and Environmental Safety Division3MCenter,Building�35-�E-91St.Paul,MN55144-1000U.S.A.1-800-�43-4630www.3M.com/OccSafety

“equivalent” to either SWPF or WPF. (3M has WPF or SWPF data for all of its

hood and helmet style products. See Technical Data Bulletin #175 for details).8

ConclusionOSHA’s final APFs, including those for half facepieces and hood/helmet style

respirators are based on the best available information and data. OSHA was bound

by law to use this procedure. The qualified APF for hoods and helmets is intended

to account for uncertainty about the performance of specific designs. Since

performance data will likely be collected on many hoods and helmets, the dual APF

may someday become unnecessary.

References1. “Assigned Protection Factors; Final Rule,” Federal Register 71:164 (24 August 2006)

pp. 50122-50192.

2. 3MOccupationalHealthandEnvironmentalSafetyDivision:“Assigned Protection Factors” 3M Regulations Update # 26 (November 2006).

3. Occupational Safety and Health Act of 1970. Public Law 91-596 (online) Available at http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=OSHACT&p_id=2743. Accessed May 3, 2007.

4. “Assigned Protection Factors; Proposed Rule,” Federal Register 68:109 (6 June 2003) pp. 34036-34119.

5. NationalInstituteforOccupationalSafetyandHealth(NIOSH): Respirator Decision Logic (DHHS/NIOSH Pub. No. 87-108). Washington, DC: U.S. Department of Health and Human Services/NIOSH, 1987.

6. AmericanNationalStandardsInstitute:American National Standard for Respiratory Protection (ANSI Z88.2). New York: American National Standards Institute, 1992.

7. CohenH.J.,Hecker,L.H.,Matthies,D.K.,Johnson.J.S.,Bierman,A.H.,Foote,K.L.: Simulated workplace protection factor study of powered air-purifying and supplied air respirators AIHAJ 62(5):595-604 (2001).

8. 3MOccupationalHealthandEnvironmentalSafetyDivision:“Assigned Protection Factors (APF) for 3M™ Hoods and Helmets” 3M Technical Data Bulletin # 175 (October 2006).

For more information, please contact Health and Safety ServicesTechnicalAssistance:1-800-�43-4630Fax-on-Demand:1-800-646-1655Internetsites:www.3M.com/OccSafetywww.respexam.com

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