Preventive safety requires careful selection of equipment, especially motors, in hazardous oil and gas recovery, chemical and petroleum refining plants, and mining environments.

Motors can cause explosions in one of two ways:

The surface of the motor can become so hot during operation that it ignites vapors, gases, or dust.

A single arc caused by motor failure (such as winding insulation failure or power supply issues) ignites surrounding materials.

There is a need for explosion-proof motors in industrial applications where highly flammable and ubiquitous materials are present. Explosion-proof does not mean that the motor will never explode, nor does it mean it is immune to external explosions. Rather, explosion-proof motors are designed to prevent internal motor explosions from igniting a larger combustible atmosphere.

Explosion-proof motors that comply with UL certification can be clearly identified by the UL listing nameplate affixed to the motor housing. The nameplate defines the motor's rating, division, and combination compliance.

To obtain certification and a nameplate, the candidate motor must meet the testing standards specified by industry standards UL — 674: Motors and generators for hazardous (classified) locations. Manufacturers submit the expected operating specifications of the candidate motor, such as RPM, torque, power, and frequency, along with descriptions of related equipment, such as variable frequency drives (VFDs). UL creates destructive tests to determine the motor's temperature rise and ensure the motor meets UL certification standards.

UL certifies motors with different ratings and classifications suitable for specific applications and material exposures.