Intrinsic safety Intrinsic safety:
The identifying letter for intrinsic safety is “i” followed by either “a” or “b is defined as a type of protection where any spark or thermal effect is incapable of causing ignition of a mixture of flammable or combustible material in air under prescribed test conditions.

This method is also recognized in division-classified areas. Because of the energy limits, this method can be used only with very low-power circuits - primarily instrumentation and signaling. The energy limits must be maintained under specified failure modes.

LocationsLocations:
This protection technique shall be permitted for apparatus and associated apparatus in Class I, Zone 0, Zone 1, or Zone 2 locations for which it is listed. Because the ignition energy varies for different flammable gases and vapors, intrinsic safety equipment must be listed for the specific material and zone.

A typical intrinsic safety barrier that limits energy to the hazardous location. (Courtesy of Cooper Crouse-Hinds)

 

NOTE: This is an unformatted excerpt from our online fire protection training library.