Explosives are hazardous by themselves, but around electricity they become even more dangerous: an arc, spark, or hot surface can easily touch off an explosion. Therefore, the electrical installation shall contain these ignition sources or house them in an area well separated from the explosives storage area.

The electrical installation shall prevent accidental ignition of flammable liquids, vapors, and dusts in the atmosphere. In addition, because portable electrical equipment is often used outdoors or in corrosive atmospheres, its material and finish should be such that maintenance costs and shutdowns are minimized. (See Figure 5-2.)

Figure 5-2. Arcs and sparks are sources of ignition that produce enough heat to cause an explosion if the air and gas mixture is between the lower and upper flammable limits of the liquid involved.