Explosion proof is a method of containing sparks within a small housing, and allowing the expanding gasses escape into the atmosphere only once they are cooled. This keeps the spark from turning into a fire or explosion. The wiring to support this method is quite involved and expensive as everything has to go through sealed conduit. This protection method is necessary for high powered devices such as pumps.
Intrinsic safety prevents sparks, fires, and explosions by never allowing enough current in the electronics to cause a spark or generate heat. The sensors are designed to operate on this low current, and an electrical barrier is placed between the sensor and the power source to control the current and eliminate surges and spikes. This protection method is safer and typically less expensive to wire.
Divisions and Zones are the result of two methods to express similar ideas. They each describe the constancy of the hazardous mixture in a hazardous area. Divisions are used in the US, and divide hazards into two categories:
Div 1 is an area where the threat of fire or explosion is possible under normal operating circumstances. This includes normal maintenance and repair operations.
Div 2 is an area where the threat is only possible under abnormal circumstances, like equipment failure.
Zones are used in Canada, Europe, and many other places. This method divides hazards into three categories:
Zone 0 describes a constant threat under normal circumstances.
Zone 1 describes an intermittent threat under normal circumstances.
Zone 2 is an area where the threat is only possible under abnormal circumstances.
