NEMA terms defined: 

NEMA 1 enclosures are typically used for protecting controls and connections/terminations from objects and personnel. This style of enclosure, while offering a latching door, does not have a gasket sealing surface. NEMA 1 enclosures are typically used in applications where sealing out dust, oil, and water is not required. Motor start/stop stations are often housed in NEMA 1 enclosures. 

NEMA 3R enclosures are typically used in outdoor applications for wiring and junction boxes. This style of enclosure provides protection against falling rain, sleet, snow, and external ice formation. Indoors they protect against dripping water. This style of enclosure does not have a gasket sealing surface. Some NEMA 3R models have hasps for padlocking. 

NEMA 3S enclosures are intended for outdoor use primarily to provide a degree of protection against windblown dust, rain, sleet, and to provide for operation of external mechanisms when ice laden. 

NEMA 4 enclosures are used in many applications where an occasional wash‐down operation occurs or where machine tool cutter coolant is used. NEMA 4 enclosures also serve in applications where a pressurized stream of water will be used. NEMA 4 enclosures contain gaskets, and the door of the enclosure is clamped for maximum sealing. They have continuous hinges, mounting feet, and padlock hasps. NEMA 4 enclosures are available in sizes from small wall mounts to two‐door floor mount enclosure models. 

NEMA 4X enclosures are made of stainless steel or high‐quality plastics. NEMA 4X enclosures are typically used in harsher environments than the standard NEMA 4 types. Applications where corrosive materials and caustic cleaners are used necessitate the use of a NEMA 4X enclosure. Applications include food, such as meat/poultry processing facilities, wherein total wash‐down operations using disinfectants are a necessity for safety. These operations occur repeatedly, such as in petro‐chemical facilities, including offshore petroleum sites. NEMA 4X is used when protection from the worst environments is required. NEMA 4X enclosures are available in sizes from small wall mounts to two‐door floor mount models. 

NEMA 6P enclosures are intended for both indoor and outdoor use, primarily to provide a degree of protection against the entry of water during prolonged submersion at a limited depth. 

NEMA 12 enclosures are designed to prevent the ingress of dust, water, and oil. 

Note: NEMA 12 enclosures are most often used for indoor applications of automation control and electronic drive systems. Some examples are packaging, material handling, non‐corrosive process control, and manufacturing applications. Doors with gaskets seal the enclosure’s contents from airborne contaminants and non‐pressurized water and oil. NEMA 12 enclosures are available in sizes from small wall mounts to two‐door floor mount models. 

NEMA 13 enclosures are intended for indoor use primarily, to provide a degree of protection against dust, spraying of water, oil, and non‐corrosive coolant. 

Some enclosures may have multiple ratings. For instance: 

3R, 12 – Outdoor use; able to be used indoors with modifications 

4, 12 – Outdoor use; able to be used indoors with modifications 

4X, 3RX – Outdoor use; able to be used indoors with modifications 

4, 9 – Can be used in both hazardous and non-hazardous locations