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.