Group B

Atmospheres containing hydrogen or gases or vapors of equivalent hazard such as manufactured gas

acrolein (inhibited) (2)
arsine
butadiene (1)
ethylene oxide (2)
hydrogen
manufactured gases containing more than 30% hydrogen (by volume)
propylene oxide (2)
propylnitrate

(1) Group D equipment shall be permitted for this atmosphere if such equipment is isolated in accordance with Section 501-5(a) of National Electric Code by sealing all conduit 1/2 inch size or larger.

(2) Group C equipment shall be permitted for this atmosphere if such equipment is isolated in accordance with Section 501-5(a) of National Electric Code by sealing all conduit 1/2-inch size or larger.