Areas which are considered always hazardous because flammable gases or vapours will be present all or most of the time under normal conditions

 Areas which are considered hazardous only infrequently as a result of ruptures, leaks or other unusual circumstances

 Equipment which creates sparks or arcs as a result of normal use. An ordinary light switch is an excellent example of a device that arcs during normal use

Equipment which creates sparks or arcs only at the instant of failure. The common induction motor used to drive most refinery pumps is an example of such equipment which normally operates for a number of years without failure

نویسنده: مهندس هادی بیات کارشناس مهندسی بهداشت حرفه‌ای

منابع مورد استفاده:

British Petroleum Company