Intrinsically safe equipment is defined as "equipment and wiring which is incapable of releasing sufficient electrical or thermal
energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited
concentration." (ISA-RP12.6) This is achieved by limiting the amount of power available to the electrical equipment in the hazardous
area to a level below that which will ignite the gases.
In order to have a fire or explosion, fuel, oxygen and a source of ignition must be present. An intrinsically safe system assumes the
fuel and oxygen is present in the atmosphere, but the system is designed so the electrical energy or thermal energy of a particular
instrument loop can never be great enough to cause ignition.
TP7C/TP9 Hazardous
Location application:
Zone 0: Where ignitable concentrations of flammable gasses vapors or liquids can exist all of the time or for long periods of time under normal operating conditions.
Zone 1: Where ignitable concentrations of flammable gasses vapors or liquids can exist some of the time under normal operating conditions.