There are two apparatus groups for gas/vapour environments:
Group I covers the use of equipment in underground mining environments where methane is present.
Group II covers all other environments
Group II is further divided into subgroup IIA, IIB or IIC:
- IIA - propane (least incendiary)
- IIB - ethylene (more incendiary)
- IIC - hydrogen and acetylene (most incendiary)
Apparatus Groups are sometimes referred to, erroneously, as ‘Gas Groups’.