NFPA 20 Fire Pump Certification Practice Exam

Dust-ignition-proof motors are designed for environments with ignitable dust. They have a totally enclosed housing that keeps dust out and prevents internal sources of heat, arcs, or sparks from igniting any dust outside the motor. That combination—excluding dust and preventing internal ignition sources—is what defines this rating, making it the correct description. Dripproof motors focus on preventing liquid water from entering the enclosure, not on preventing ignition by dust. Dripproof guarded motors add protective features but still aren’t specifically about stopping dust ignition. Explosion-proof motors are built to contain internal explosions and prevent ignition of flammable gases or vapors outside the enclosure, which is a different hazard scenario than dust ignition in a dusty environment.