In NEFPA 70E Table 130.7 (C) (10) footnote, a cat 3 rating can be obtained by using 2 sets of fr coveralls with the inner rated at 4 and the outer rated at 5 over non melting or untreated natural fiber clothing. There is no explanation for allowing this in the article. In order to meet the cat 3 level table 130.7 (C) (11) requires a fr coverall with a rating of 25.
Since a fr 4 and fr 5 do not equal 25, there must be some additional protection by layering clothing, but the code article does not explaian what it is.
Can anyone explain the formula that the author of the tables are using in footnote 9?
If I would wear a fr 8 rated coverall over a fr 8 shirt and fr 8 pants, would I be able to meet the same protection stated in footnote 9?
Since a fr 4 and fr 5 do not equal 25, there must be some additional protection by layering clothing, but the code article does not explaian what it is.
Can anyone explain the formula that the author of the tables are using in footnote 9?
If I would wear a fr 8 rated coverall over a fr 8 shirt and fr 8 pants, would I be able to meet the same protection stated in footnote 9?