Please help: Motor Constructionction NEMA Vs IEC

[etgbccc2003]

Dear Sir,

In IEC, there's a Ex 'n' and Ex 'e' construction. However, in NEMA, what's the equivalent?

If we need to use a motor in class 1 division 2 area with possibility of hydrogen (Group B). How can we specify for a NEMA frame-size motor?

Thanks.

Regards
etgbccc