46 CFR § 108.187 - Ventilation for brush type electric motors in classified spaces.

Ventilation for brush type electric motors in classified locations must meet N.F.P.A. 496–1974 “Standard for Purged and Pressurized Enclosures for Electrical Equipment in Hazardous Locations”, except audible and visual alarms may be used if shutting down the motors may cause unsafe conditions.