These Groups are sub-divided into Categories, as shown below. The way in which this categorisation has been developed highlights one of the main distinctions of Group I and II. For Group I, the categorisation depends on (amongst other factors) whether the product is to be deenergised in the event of an explosive atmosphere occurring. For Group II, it depends where the product is intended to be used in and whether a potentially explosive atmosphere, is always present, or is likely to occur for a long or a short period of time. Group I: Underground and above ground installations for mining industry with hazardous choke damp and mine dust Category Accepting Category M1 Very high level of protection Safety in the event of two faults occurring independently of each other Category M2 High level of protection Device must be turned off in case of potentially explosive atmosphere Group II: Other ex-areas Category Accepting of danger Accepting Zone Substance class Category 1 Highly likely to occur and are present continuously, for long periods of time or frequently Very high level of protection Safety in the event of two faults occurring independently of each other Zone 0 G (Gases) Zone 20 D (Dusts) Category 2 Likely High level of protection Safety in the event of one fault Zone 1 G (Gases) Zone 21 D (Dusts) Category 3 Unlikely Normal level of protection Suitable for normal operation Zone 2 G (Gases) Zone 22 D (Dusts) Group I comprises equipment intended for use in the underground parts of mines, and to those parts of surface installations of such mines, likely to become endangered by firedamp and/or combustible dust. Group II comprises equipment intended for use in other places likely to become endangered by explosive atmospheres. INTERESTING FACTS & APPROVALS ATEX groups & catagory of equipment
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