A hazardous area is an area where flammable liquids, vapours, gases or combustible dusts are likely to occur in sufficient quantities to cause fire or explosion.

There are three basic conditions that must be satisfied to create a fire or explosion.

1. Flammable or combustible material – such as  flammable liquid, vapour or combustible dust must be present in sufficient quantity and concentration.
2. Oxygen
3. Ignition source

Hazardous area electrical equipment works by suppressing or separating one or more of these  three components to avoid a fire or explosion. Where suppression cannot be done the use of explosion containment Ex d is used.