FIT TESTING FAILS TO INDICATE ADEQUACY OF FIT FOR INDIVIDUAL WEARERS

Transcription

1 FIT TESTING FAILS TO INDICATE ADEQUACY OF FIT FOR INDIVIDUAL WEARERS Robin Howie Robin Howie Associates Edinburgh Scotland ISRP Conference, Prague, 2014

2 WHAT IS FACEPIECE FIT TESTING? Fit tests are used to help select a specific respirator for a person. If a person passes the test, they are assumed to have a respirator that fits. It is assumed that subsequent respirator use will provide a level of protection equal or greater than the assigned protection factor. Nelson & Mullins, JSIRP, 2004

3 WHAT IS FACEPIECE FIT TESTING? Fitting tests identify gross misfits only and do not guarantee adequacy of fit. BS 4275:1997

4 WHAT IS FACEPIECE FIT TESTING? Fit tests help select a specific respirator for a person Fit testing identifies gross misfits only Which is correct, or is neither correct?

5 ERROR IN FIT TEST DATA Before assessing the Fit Test and WPF literature it is essential to address a critical factor in both Fit Test and WPF studies.

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7 IN-MASK SAMPLING With a face seal leakage of nominally 6.5%, (i.e. a FF of 15) calculated FF of between 6 and 100 were obtained depending on the position of the probe and the site of the leakage path. Bostock (1988)

8 IN-MASK SAMPLING Bostock (1988) led to adoption of a large diameter deep probe in all relevant European Standards.

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10 EFFECT OF PROBE TYPE ON FFP3 FF DEVICES Note that with a Liu probe on the inside surface of a filtering facepiece device during inhalation the probe measures only filter penetration and during exhalation measures that proportion of the inhaled aerosol that has not deposited in the body.

11 EFFECT OF PROBE TYPE ON FFP3 FF Howie (2002) Leak Large Dia Liu Liu Pos n Deep Surface Deep Temple Chin Neck

12 EFFECT OF PROBE TYPE: CONCLUSION Non-Bostock in-mask probing can introduce underestimates of in-mask contaminant levels by up to a factor of 20 and can therefore overestimate QnFF by the same factor.

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14 EFFECT OF PROBE TYPE- POSITION: CONCLUSION Most WPF and QnFF data from the USA are derived from non- Bostock in-mask probing and are therefore likely to overestimate WPF or QnFF.

15 LITERATURE SEARCH The WPF literature was searched for papers which provided data which permitted the relationship between QnFF and WPF to be determined or in which the author(s) comment on analysis of such.

16 COMMENTS IN THE LITERATURE Quantitative fit testing cannot be used to quantitatively predict workplace performance of respirators for an individual. Dixon & Nelson (1984)

17 COMMENTS IN THE LITERATURE The lack of a demonstrated association between quantitative fit factors obtained by these PAPRs and the level of protection they provide in the workplace brings into question the appropriateness of using quantitative fit factors as presently determined as the original basis for the PAPR classification of of Myers et al (1984)

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20 ANALYSIS OF MYERS et al (1984) DATA Analysis demonstrated that there was neither a useful correlation nor a useful ranking relationship between QnFF and WPF.

21 COMMENTS IN THE LITERATURE No relationship was found between the Quantitative Fit Factors measured by the Portacount and the WPF obtained for dual cartridge half-mask negative pressure respirators. Gaboury and Burd (1989)

22 COMMENTS IN THE LITERATURE The quantitative fit factors that were obtained did not predict which workers would have the highest or lowest WPF. Although the data were limited, it appears there was no correlation between WPF and the quantitative fit factor. Colton, Johnston, Mullins et al (1989)

23 COMMENTS IN THE LITERATURE No significant correlation between the WPF values and the quantitative fit testing data were found in this study. Myers, Zhuang, Nelson et al (19??)

24 COMMENT What caused Tom Nelson and Haskel Mullins to change their minds??

25 COMMENTS IN THE LITERATURE FF was shown to be a meaningful indicator of respirator performance in actual workplace environments. Zhuang et al (2003)

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27 ANALYSIS OF ZHUANG et al (2003) data Analysis of the raw data demonstrate that QnFF and WPF <100 were highly correlated. For QnFF >100 the the data were poorly correlated.

28 ANALYSIS OF ZHUANG et al (2003) data Repeatability of QnFF data: Wearer 3 19, 18, 13, 10 Wearer 6 246, 70, 62, 11 Wearer , 126, 15 Wearer , 228, 76, 15 Wearer , 587, 80

29 ANALYSIS OF ZHUANG et al (2003) data The repeatability of QnFT results is poor. It would therefore be prudent to re-test at least once every subject who gives a result below about a factor of 20 above the criterion.

30 ANALYSIS OF HOWIE et al (1996) data In a WPF study of PAPR during asbestos removal operations investigators undertook the standard CEN leakage test to identify suitable PAPR and the WPF for the investigators were also measured.

31 ANALYSIS OF HOWIE et al (1996) data All but one of the investigators achieved QnFF>50,000 for all 4 of their study respirators as measured for the same individual respirators using the same 20 mm dia deep in-mask probes as used during the field study.

32 ANALYSIS OF HOWIE et al (1996) data One investigator, J, a female with fine features, was able to achieve an adequate laboratory fit (FF>10,000) with one mask type only. She wore only this mask during the study.

33 ANALYSIS OF HOWIE et al (1996) data Investigator WPF Investigator n WPF range H >2k J >2k T >2k W >2k

34 ANALYSIS OF HOWIE et al (1996) data Investigator 75 th percentiles* H 276 J 231 W 130 * Data were too sparse to permit estimation of >75 th percentiles

35 ANALYSIS OF HOWIE et al (1996) data Statistically, both the investigators, who had had QnFT, and the workmen, who had not had QnFT, achieved 95%ile WPF of ~40.

36 ANALYSIS OF HOWIE et al (1996) data Given that all investigators had achieved QnFF >10,000, the finding of a 95 th percentile WPF of ~40 demonstrates that QnFF failed to indicate real-world WPF in this study.

37 SUMMARY Only one published study claims to have demonstrated a useful relationship between QnFF and WPF.

38 CONCLUSION On the available data QnFT cannot be used to identify that a given facepiece fits a given individual. However, it may be able to identify gross misfits.

39 SO WHAT? If an individual is given an impression that his RPE provides a good fit he may put himself at risk by failing to minimise contaminant emissions and/or may enter areas he would otherwise avoid.

40 SO WHAT? Fit Testing may therefore put the wearer at avoidable risk.

41 HOWEVER Fit testing is an excellent indoctrination and training aid and mandatory provision of Fit Testing at least ensures that each individual worker has received training.