To understand explosion proof, you need to look at the context of the term and the organization that defined it. The National Fire Protection Association (NFPA) began publishing the National Electric Code (NEC) in 1897. The NEC is also known as NFPA 70 and ANSI/NFPA 70 from its inclusion in the body of NFPA codes. The NEC includes definitions for several types of protection techniques acceptable when designing products for use in hazardous (classified) locations: Explosion proof, dust ignition proof, dust tight, purged/pressurized, intrinsically safe, and hermetically sealed. These definitions set the criteria that must be met by all components installed or used in hazardous (classified) locations.