Post on 19-Jan-2016
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ASSIGNED PROTECTION FACTORS AND ISO
PROTECTION LEVELS
Robin Howie
Robin Howie Associates
ISRP, York, April 2013
There are known knowns.These are things we know we know.There are known unknowns.That is to say, these are things we know we don’t know.But there are also unknown unknowns.These are things we don’t know we don’t know.
Donald Rumsfeldt
THE ISO DTS 16973 CLASSIFICATION REGIMEN
Determine max Lab TIL;
Compare max TIL with Table 2 and assign to relevant TIL Level;
Apply the “Safety Factor” relevant to the TIL Level;
Determine the Protection Level (PL) Class.
TABLE 18: Protection level classes
TIL max (%)
Safety Factor
Protection Level
Class
0.001 10 10,000 PL6
0.01 5 2,000 PL5
0.1 4 250 PL4
1 3.3 30 PL3
5 2 10 PL2
20 1.25 4 PL1
OBSERVATION
From personal experience most “high” performance devices give
much lower Lab TIL than the maxima specified in the EN.
So, Lab PF may be higher than the relevant EN NPF for such devices.
OBSERVATION
PL5 is effectively equivalent to current TM3 and full-face –ve
pressure P3.
A more stringent assessment of the data would set the APF for these devices at somewhere around 20.
OBSERVATION
PL5 effectively sets the “NPF” for these devices at 2000 whereas
BS4275 set the APF at 40.
OBSERVATION
The draft ISO classification takes no account of the nature of the device
and therefore fails to address factors that could affect performance in the
workplace, e.g. sweating during heavy work and/or in hot conditions is likely to be more deleterious with ½-mask -ve performance than with
ff-ve or PAPR.
OBSERVATION
Consider the case where YOU may be exposed to, say, 50 fibres/ml of amosite, and you are offered 3 devices fitted with P3 filters,
all meeting ISO PL5:
a ½-mask -ve pressure device; a full-mask -ve pressure device;
and, a full-mask TM3.
QUESTION
How many would choose the
½-mask -ve pressure device?
QUESTION
How many would choose the
full-mask -ve pressure device?
QUESTION
How many would choose the
full-mask TM3?
OBSERVATION
Consider a full-mask PAPR that gave a max TIL of 0.003%: i.e. a Lab PF of 33,000;
The device would be assigned to an ISO TIL class of 0.01%, i.e. a PF of 10,000;
The ISO Safety Factor would be 5, so giving an ISO “NPF” of 2,000.
OBSERVATION
But a known known is that WPF measured for such devices using suitable in-mask sampling probes give 95%iles in the
region of 20-100.
OBSERVATION
The current ISO draft would therefore take us back 20 years to effectively selecting RPE on the basis of NPF.
WPF DATAThere is a fundamental error in how data are presented
for WPF studies that involve continuous in-mask sampling. For the inhale part of the sample duration
in-mask contaminant is collected. For the exhale part only the non-body deposited contaminant is collected. If all of the contaminant deposits in the
body the true WPF is half of the reported WPF. For continuous flow powered or air-fed devices any
exhaled contaminant will be diluted by the incoming air; and the true WPF will be about half
of the reported WPF.
WPF DATA
It would be prudent to half all WPF results from studies with continuous in-mask sampling; including the data from
Howie et al (1996).
WPF DATA
I proposed such correction when drafting of BS4275 but, as such correction would have “rolled down” into setting very low APF for FFR and ½-mask devices, the proposal was
rejected.
WPF DATA
The then available WPF data were evaluated when setting the APF for
BS4275: copies of these data should be available in the BSI archives. If not
available from BSI the relevant references were cited in BS4275.
Further WPF data are now available.
WPF DATA
A major problem, addressed in BS4275, is that most WPF studies carried out in the USA use/used in-mask probes that are
likely to have significantly under-measured in-mask concentrations and therefore caused WPF to be significantly over-
estimated.
POSSIBLE PROBE EFFECTS
PAPR FF-veP3
UK 14-130
Howie et al (1996)
16-50
Tannahill (1991)
US 728
Colton et al (1990)
95
Colton et al (1989)
WPF DATA
WPF derived from US studies must therefore be assessed with care.
A KNOWN KNOWN
“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 quantitative fit factor.” Colton et al (1989).
8.8.1 “Fitting tests only identify gross misfits and do not guarantee adequacy of fit.” BS4275: 1997
A KNOWN KNOWN
The Zhuang et al (2003) and Han (2002) studies reported correlation between WPF and QnFF.
Zhuang et al studied the correlation over a short period and did not address long-term effects.
Han’s r^2 values for FF <100, the normal “pass” criterion for such devices, was 0.31 and for FF
>100 was 0.02.
A KNOWN KNOWN
The Zhuang et al (2003) and Han (2002) studies reported correlation between WPF
and QnFF. Zhuang et al’s data exhibit declining
correlation as FF increases above 100.
Han’s r^2 values for FF <100, the normal “pass” criterion for such devices, is 0.31
and for FF >100 is 0.02.
ASSUMPTION
Where QnFF are available but Lab PF data are not, it will be assumed that QnFF can used as an indicator of likely
Lab PF.
CALCULATION BASIS
“Required Safety Factors” below will be based on ISO TIL class/95th%ile WPF
AVAILABLE WPF DATA
Howie et al (1996)
4 x TM3 devices
Large diameter deep probe
No Fit Testing for workmen.
All investigators achieved QnFF >10,000
Howie et al (1996)
Work men Invest’r
Device R1 (62) R2 (65) R3 (33) All (177) All (62)
Lab PF >10000 >10000 >10000 >10000 >10000
QnFF na na na na >10000
ISO PF 10000 10000 10000 10000 10000
ISO SF 5 5 5 5 5
ISO PL 2000 2000 2000 2000 2000
95% WPF 40 130 14 40 40
Req’d SF 250 80 670 250 250
AVAILABLE WPF DATA
Riala & Riipinen (1998)6 x PAPR, P3, assumed TM3
Small diameter probe, depth not defined.No Fit testing
-----------------------------------------------------Colton et al (1989), PAPR
Liu probe effectively flush with inner surface of inner cupAll QnFF >1000
Riala & Riipinen, Colton et al (1990)
R&R Colton et al
Device PAPR (31) PAPR (20)
Lab PF >2000 na
QnFF na >1000
ISO PF 1000 1000
ISO SF 4 4
ISO PL 250 250
95% WPF 5 >700
Req’d SF 200 -
AVAILABLE WPF DATA Tannahill (1990, 1991)
3 x Full-mask –ve AP with P3 filtersSampling in visor area
No Fit Testing--------------------------------------------
Colton et al (1989)Full-face –ve
Liu probe effectively flush with inner surface of inner cup
All QnFF >500
Tannahill, Colton et al (1989)
Device A (33) B (28) All (67) _ve
Lab PF >10000 >10000 >10000 na
QnFF na na na >500
ISO PF 10000 10000 1000 100
ISO SF 5 5 5 3.3
ISO PL 2000 2000 2000 30
95% WPF 16 50 20 95
Req’d SF 600 200 500 -
Source Tannahill Colton
AVAILABLE WPF DATA
Myers et al (1984)
2 x loose-fitting AP PHR
Probe on inside surface of vizor opposite mouth
Minimum QnFF >1000
Myers et al (1984)
Device AH3 (22) W-344 (23) Both (45)
Lab PF na na na
QnFF >2000 1200 1200
ISO PF 1000 1000 1000
ISO SF 4 4 4
ISO PL 250 250 250
95% WPF 37 20 30
Req’d SF 30 50 30
AVAILABLE WPF DATA Zhuang et al (2003)
2 x ½masks -ve with P100 filtersProbably shallow Liu probe
ZZ very kindly supplied raw dataStudy deliberately included wearers with
QnFF <100Only data for wearers with QnFF >100
analysed herein
Zhuang et al (2003)
Device 3M 6000
(23)
MSA Comfo ll
(20)
Both
(43)
Lab PF na na na
QnFF >100 >200 >100
ISO PF 100 100 100
ISO SF 3.3 3.3 3.3
ISO PL 30 30 30
95% WPF c20 c50 c50
Req’d SF 5 2 2
AVAILABLE WPF DATA
Myers & Zhuang (1998)
3 x ½ mask DFM, 2 x FFR DM, 8-11 subjects per mask type
Probe probably on inside surface of mask
All QnFF >100.
Myers & Zhuang (1998)
Device Gerson & MSA (20)
All (54)
Lab PF na na
QnFF >100 >100
ISO PF 100 100
ISO SF 3.3 3.3
ISO PL 30 30
95% WPF c20 45
Req’d SF 5 2
AVAILABLE WPF DATA
Hery et al (1993)
2 x FFP2, 3 x ½-mask P2,
1 x ½-mask P3
Flush probe
No Fit Testing
Hery et al (1993)
Device FFP2
(29)
FFP2
(30)
½+P2
(29)
½+P2
(29)
½+P2
(30)
½+P3
(30)Lab PF 37 20 125 17 13 200QnFF na na na na na naISO PF 20 20 100 5 5 100ISO SF 2 2 3.3 1.25 1.25 3.3ISO PL 10 10 30 4 4 3095% WPF 2 2 2 2 2 2Req’d SF 10 10 50 2 2 50
AVAILABLE WPF DATA
Liu et al (2006)
2 x ½ mask OV
Probe on inner surface of mask
QnFF with pass level of 100, FF for 3M device ranged 155-15000
FF for Survivair device ranged
219-76000
Liu et al (2006)
Device 3M SurvivairLab PF na naQnFF 155 212ISO PF 100 100ISO SF 3.3 3.3ISO PL 30 3095% WPF rank 47 9Req’d SF 2 10
AVAILABLE WPF DATAHan (2002)
3 x N95 FFR
Probe probably on inner surface of mask
QnFF 10-200
Han (2002)
Device 3M 8511 MSA FR200 Wilson 10FLLab PF na na naQnFF 20 5 10ISO PF 20 5 5ISO SF 2 1.25 1.25ISO PL 10 4 495% WPF 6 2 3Req’d SF 3 2 2
Summary
The known knowns.
TM3, FF-ve AP
Device TM3 TM3 FF-ve
LabPF/QnFF >10000 >2000 >10000
ISO SF 5 4 5
WPF based SF
80-670 200 200-600
Source Howie ea Riala & Riipinen
Tannahill
PHR, ½-mask, FFR
Device PHR ½
P100
½-veP3
½-veP2 FFP2
LabPF/ QnFF
>1200 >100 200 13-125 20-37
ISO SF 4 3.3 3.3 1.25-3.3
2
WPF based SF
30-50 2-5 50 2-50 10
Source Myers ea
Zhuang
ea
Hery
FFR, ½-mask -ve AP
Device Gerson & MSA
All OV OV N95
LabPF/ QnFF
>100 >100 155 212 >40
ISO SF 3.3 3.3 3.3 3.3 2-3.3
WPF based SF
5 2 2 10 5-10
Source Myers & Zhuang Liu et al Han
Known unknowns
What are the effects of higher then moderate work rates on TIL?
(See TNO data on Gas Masks and consider the sweating of wearers working hard; particularly when wearing impervious clothing.)
CONCLUSION
The current draft ISO classification regimen fails to address the WPF data base and is
therefore highly likely to put RPE wearers at unnecessary, avoidable, and thus negligent, risk: particularly for the
nominally “high” performance AP devices.