The 70E states that HC4 PPE is "Arc-rated FR shirt and pants or FR coverall, and arc flash suit selected so that the system arc rating meets the required minimum" (Table 130.7(C)(11)). Since I normally wear HC2 clothes anyway, I never really put much thought into this. But in looking at it closer, do you think it is acceptable to wear HC0 clothing under a flash suit that is rated for 40 cal/cm2? This "system" meets the required minimum but does not include the FR Shirt and pants called out in the description. Comments?

TxEngr

I've wonder the same question. The code clearly states that its purpose is to limit skin exposure to 1.2 cals. FR clothing is tested to limit internal exposure to 1.2 cal (but only at 50% probability). I talked with an Oberon exec once who told me you could be in your underwear as long as the clothing met the IE level.

The arguement could be made for which method you choose, IEEE or Table. If you do the analysis, the obligation is for the clothing to meet or exceed the IE, and that could be with just the one outer layer. If you conform to the Table method, then the arguement could be made that the additional layers are specified in the HRC definition so they are required.