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Hazardous area (on account of explosive gas atmospheres) called “hazardous locations” in the US, is an area (3-dimensional) in which an explosive gas atmosphere is or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of equipment.

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Hazardous areas are classified into 3 zones based upon the frequency of occurrence and duration of an explosive gas atmosphere, as follows:
 

Zone 0

• Area in which an explosives gas atmosphere is present continuously, for long periods, or frequently

• 1000 hours per year or more (10%) flammable mixture present

 

Zone 1 

• Area in which an explosive gas atmosphere is likely to occur in normal operation occasionally

• Between 10 and 1000 hours per year or more (0.1% to 10%) flammable mixture present

 

Zone 2

• Area in which an explosive gas atmosphere is not likely to occur in normal operation, but if it does occur, will persist for a short period only

• Less than 10 hours per year (0.01% to 0.1%) flammable mixture present

 

Non-hazardous area (safe area)

• A non-hazardous area is an area in which an explosive atmosphere is not expected to be present.

• Less than 1 hour per year (less than 0.01%) flammable mixture present