Page 54 - Occupational Health & Safety, July/August 2019

PROTECTIVE APPAREL
Chemical Barrier Tests
NFPA 1991
NFPA 1994 Class 1
NFPA 1994 Class 2 and 2R
NFPA 1994 Class 3 and 3R
Test Method
Permeation
Permeation(4)
Permeation(4)
Permeation(4)
Total Chemicals
26
(24 TIC(5) + 2 CWA(6))
11
(9 TIC + 2 CWA)
6
(4 TIC + 2 CWA)
6
(4 TIC + 2 CWA)
Liquids
20
5
2
2
Liquid Test Concentration
>95% (50% NaOH)
>95%
>95%
>95%
Liquid Test Area/ Coverage
FULL (>100 g/m2)
PARTIAL 20 g/m2
LIGHT 10 g/m2
LIGHT 10 g/m2
Gases
6
6
4
4
Gas Test Concentration
>99% (pure)
1% (10,000 ppm)
0.035% (350 ppm)
0.004% (40 ppm)
Chemical Exposure Time
60 min
60 min
60 min
60 min
TIC Requirement (cumulative mass)
<6 ug/cm2
<6 ug/cm2
<6 ug/cm2
<6 ug/cm2
Table 2: Permeation Tests Used to Qualify NFPA 1991 and NFPA 1994 Suit Materials
Notes: (4) Sulfuric acid for NFPA 1994 is only tested using penetration test, not using a permeation test. (5) TIC = Toxic Industrial Chemical (6) CWA = Chemical Warfare Agent
tion for these standards are different. For example, NFPA 1994 section 1.3.3 notes (underlines added) that Class 3 protective ensembles are “designed to provide limited protection to emergency first responder per- sonnel at hazardous materials or terrorism incidents involving low levels of vapor or liquid chemical hazards, where the concen- trations are below immediately dangerous to life and health (IDLH), permitting the use of air-purifying respirators (APR).”
A Closer Look at Required NFPA Chemical Barrier Testing
There are also differences in how chemical barrier protection is measured. Table 1 lists relative chemical protection levels. NFPA 1992 assesses chemical barrier properties versus 10 liquid chemicals using the ASTM F903 penetration test method. Because NFPA 1994 Class 4 suits are designed only for particulate hazard protection, neither permeation nor penetration material tests are used. There are six NFPA options that do use permeation testing to assess chemi- cal barrier, but there are differences in how stringent that testing is. Table 2 shows details of permeation testing required for NFPA 1991 and NFPA 1994 Classes 1, 2, and 3.
At first glance, it may appear that per- meation testing is comparable since the test duration (60 minutes) and the pass/fail re- quirement (≤6 ug/cm2) are the same. That is not the case. How permeation testing is conducted varies significantly among these standards because of the different scopes and intended performance levels of the suits. First, note the number of chemicals included in the test battery—NFPA 1991 uses 26 chemicals and NFPA 1994 Class 1, Class 2, and Class 3 use 11, 6, and 6 chemi- cals, respectively. Additionally, note that NFPA 1994 only requires sulfuric acid to be tested using a penetration test, while NFPA 1991 uses the permeation test for all 26 chemicals, including sulfuric acid.
The next difference is that NFPA 1991 uses more liquid challenge chemicals (20) and the liquid volume in contact with the material is the highest. For NFPA 1991, the liquid must fully cover the test specimen for the full duration of the test. For 1994 Class 1, droplets amounting to 20 g/m2 are applied to the material, which only partially covers the sample. For NFPA 1994 Classes 2 and 3, the liquid droplet coverage is lim- ited to just 10 g/m2.
How does gas permeation testing com-
your hazard protection needs and is also third-party certified, then certification of the CPC will add extra value.
Comparing NFPA 1991,
1992, and 1994
For CPC used in the USA, several certifica- tion standards are published by the NFPA. There are currently three main NFPA stan- dards covering hazmat PPE. These stan- dards are NFPA 1991,1 1992,2 and 1994.3 NFPA 1994 offers seven unique classes within the standard, so in all there are nine possible varieties of NFPA-certified suits for hazmat PPE. The “R” designation after NFPA 1994 Classes 2, 3, and 4 is used to denote a “ruggedized” version of each; they have higher physical strength requirements but use the same chemical barrier require- ments as the non-ruggedized versions.
Each NFPA hazmat clothing standard
covers a different scope or purpose and therefore uses different tests and require- ments. When deciding whether a CPC item certified to a NFPA standard is appropriate for your chemical exposure, it is helpful to understand how certified suits were evalu- ated. Table 1 provides a high-level overview of the nine options available from NFPA 1991, 1992, and 1994 standards, along with some key performance levels.
While many of the same tests are used in these NFPA standards, the performance limits vary significantly because of the dif- ferent scopes and expected performance levels of the suits. For example, all but two of the options require a “shower test” to evaluate liquid tight integrity of the suit/en- semble. But as noted in Table 1, the length of exposure to the shower test varies from 60 minutes to just 4 minutes. This is not surprising since the scope and/or applica-
48 Occupational Health & Safety | JULY/AUGUST 2019
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