Hazardous source list

[alisaffari]

Hi Dear experts
At first , i apologize for my English language.
I review a document about hazardous source list.recycle gas compressor (hydrogen gas) has been considered in zone 2 at this document.
is there any idea for this consideration?
is it correct?

 

[JLSeagull]

CAS No. 1333-74-0
The zone has to to with the likelyhood of the hazardous vapor and the group pertains to the type of gas. NFPA 497 lists hydrogen as Class I "Zone" Group IIC.

Within the traditional US NEC "Division" groups hydrogen is group B.