The following definitions are consistent with NFPA 496 (2013 Edition), Standard for Purged and Pressurized Enclosures for Electrical Equipment.

Type-X Purge and Pressurization – Permits the use of electrical equipment suitable for unclassified locations within the respective protected enclosure where the equipment would otherwise be required to be suitable for Division 1 or Zone I locations.

Per NFPA 496 , Type-X reduces the classification with an enclosure from Division 1 to unclassified

Type-Y Purge and Pressurization – Permits use of electrical equipment suitable for Division 2 or Zone 2 locations with the protected enclosure where the equipment would otherwise be required to be suitable for Class I and II, Division 1 or Zone 1 locations.

Per NFPA 496 , Type-Y reduces the classification with an enclosure from Division 1 to Division 2

Type-Z Purge and Pressurization – Permits use of electrical equipment suitable for unclassified locations with the protected enclosure where the equipment would otherwise be required to be suitable for Class I and II, Division 2 or Zone 2 locations.

Per NFPA 496 , Type-Z reduces the classification with an enclosure from Division 2 to unclassified

For access to the complete NFPA 496 Standard for Purged and Pressurized Enclosures for Electrical Equipment contact the National Fire Protection Association online at nfpa.org or call 1-800-344-3555 (outside the US call 1-617-770-3000).

Hazardous Area Classifications

The purpose of a purge and pressurization system is to ensure compliance to specific safety standards for electrical equipment used in, around, or near an atmosphere with flammable gases or vapors, flammable liquids, combustible dusts, ignitable fibers or filings, where there is a risk of an explosion or fire.

Therefore, when selecting a purged and pressurization system, it’s important to have an understanding of the Class/Division System or Zone System used in defining these hazardous areas where the propensity for an explosion or fire exists.

Presently, two systems are used to classify hazardous areas: the Class/Division System used in the United States and Canada and the Zone System used in the rest of the world.

Additional Terms

MIC ….. Minimum Igniting Current (Ratio) >>more info>>

MESG….Maximum Experimental Safe Gap >>more info>>

SCFH ….. Standard Cubic Feet per Hour >>more info>>

SCFM….Standard cubic feet per minute >>more info>>

Hall Effect Sensor …. (as used AB-CO PURGE pressure switches DP-1B and DP-1C) is a transducer that varies its output voltage in response to a magnetic field. >>more info>>