1 : General-purpose - Indoor protection against limited amount of falling dirt
2 : Drip-tight - Indoor protection agains limited amounts of falling water and dirt
3 : Weather-resistant - Protects against dirt, dust, rain, sleet and snow, and is undamaged by the formation of ice
3R : As 3, but omits protection against windblown dust
3S : As 3, but also operable when laden with ice
3X : As 3, but indicates additional corrosion protection; commonly used near salt water
4 : Watertight - Must exclude at least 65 GPM of water from a 1 in nozzle delivered from a distance not less than 10 ft for 5 min
4X : Similar to 4, with additional corrosion protection
5 : Dust-tight - Provided with gaskets or equivalent to exclude dust; used in steel mills and cement plants
6 : Temporarily submersible in water or oil; used in quarries, mines, and manholes
6P : Withstands occasional prolonged submersion. Not intended for continuous submersion
7 : Explosion-Proof - Certified for indoor use in Class I, Groups A, B, C, and D environments as defined in NFPA/NEC
8 : Oil Immersed - Certified for indoor/outdoor use in Class I, Groups A, B, C, and D as defined in NFPA 70
9 : Dust Ignition Proof - Certified for indoor/outdoor use in Class II, Groups E, F, or G as defined in NFPA/NEC
10 : Mine-Safety - Meets the requirements of the Mine Safety and Health Administration, 30 CFR Part 18
12 : General-purpose - Some protection against dust, falling dirt, and dripping non-corrosive liquids
13 : General-purpose - Protection against dust, spraying of water and non-corrosive coolants
Ex e : Alternative to flameproof, intended to house components which will not generate an arc or spark during normal operation. Additional design measures are taken to prevent the possibility of excessive heat, the ingress of water or dust, and the resistance to impact, thus preventing any explosions from occurring
