Explosion must have three conditions

Ignition source: In the production process of large-scale use electrical instruments, a variety of spark friction, mechanical wear sparks, static electricity sparks, high temperature is inevitable, especially when the instrument, electrical failure.
Many industrial sites to meet the objective conditions of the explosion. When explosive substances mixed with oxygen concentration is within the limits of the explosion, if the source of explosion, an explosion will occur. So take the proof becomes very necessary.
Explosive substances: air circuit breaker  sites will have some combustible substances. About two-thirds of coal mine sites have presence of explosive substances; chemical industry, about 80% of the production workshop regional presence of explosive substances.
Oxygen: oxygen in the air is everywhere.
(1) Explosive  Electric energy meter  (flammable air flammable dust): with oxygen (air) the reaction substances, including gases, liquids and solids. (Gases: hydrogen, acetylene, methane, etc.; liquid: alcohol, gasoline; solid: dust, fiber dust, etc.)
(2) Air or oxygen (air or oxygen).
(3) ignition source (source of ignition): including open flames, electrical sparks, mechanical sparks, static electricity sparks, heat, chemical reaction, energy and so on.