Every hazardous site has areas where explosive gas is always present, sometimes present or almost never present. That frequency defines the zone — and the protection level every electrical product must meet.
Three zones. Three levels of exposure.
Zone 2Unlikely and brief
Zone 1Likely in normal operation
Zone 0Continuous
Zone 0
Explosive atmosphere is present continuously or for long periods — for example, inside storage tanks and reactors.
Zone 1
Likely to occur during normal operation, including areas around valves, discharge points and Zone 0 equipment.
Zone 2
Not likely to occur, and only for short periods — often in surrounding areas where a leak would be abnormal.
Classification is the specification.
Each zone demands a different level of equipment protection. Treating the zone as paperwork rather than an engineering input risks choosing equipment that was never designed for the actual exposure.