ATEX (Atmosphères Explosibles) is a European directive that defines the minimum safety requirements for equipment and protective systems used in hazardous environments, where there is a risk of explosion. ATEX regulations divide hazardous environments into three zones, based on the likelihood and duration of an explosive atmosphere.

Zone 0 is an area where an explosive gas atmosphere is present continuously or for long periods. This type of environment requires equipment that is intrinsically safe, meaning that the equipment is incapable of producing a spark or thermal effect that could ignite the explosive atmosphere. In zone 0, only ATEX-certified equipment specifically designed for this environment can be used.

Zone 1 is an area where an explosive gas atmosphere is likely to occur in normal operation. This type of environment requires equipment that is explosion-proof, meaning that the equipment is capable of containing an explosion within itself and preventing the explosion from spreading to the surrounding atmosphere. In zone 1, only ATEX-certified equipment specifically designed for this environment can be used.

Zone 2 is an area where an explosive gas atmosphere is not likely to occur in normal operation but may occur for short periods. This type of environment requires equipment that is non-sparking, meaning that the equipment is designed to prevent the occurrence of sparks or hot surfaces that could ignite the explosive atmosphere. In zone 2, standard equipment can be used, but it must be ATEX-certified.

Overall, the difference between ATEX zones 0, 1, and 2 is the likelihood and duration of an explosive atmosphere. In zone 0, the explosive gas atmosphere is present continuously or for long periods, in zone 1, the explosive gas atmosphere is likely to occur in normal operation, and in zone 2, the explosive gas atmosphere is not likely to occur in normal operation but may occur for short periods. The safety requirements for equipment used in each zone vary, with zone 0 being the most hazardous and requiring the highest level of protection.