A hazardous area is defined as an area in which explosive atmospheres, or may be expected to be, present in quantities such as to require special precaution for the construction and use of electrical equipment. An explosive atmosphere consists of a mixture of flammable substances with air in the form of GAS, VAPOUR OR MIST in such proportions that it can be exploded by excessive TEMPERATURES, ARCS OR SPARKS. The gases, vapours or mists will only explode when mixed with air between specific percentage mixtures, these are called:
LOWER EXPLOSIVE LIMIT (LEL)
UPPER EXPLOSIVE LIMIT (UEL)
These mixtures will also have different: auto-ignition temperatures (AIT); minimum ignition currents (MIC - intrinsic safety test apparatus); maximum experimental safe gaps (MESG - relates to flameproof enclosures flame path), depending upon the substances contained within the mixture.

EXAMPLES OF EXPLOSIVE MIXTURES
Substance LEL UEL MESG MIC AIT
(%) (%) mm mA (°C)
Methane 5 15 1.14 195 595
Propane 2 9.5 0.97 146 470
Ethylene 2.7 34 0.65 108 425
Acetylene 3 17 0.25 60 305
Hydrogen 4 75.6 0.28 75 560

We offer a variety of flammable gas detection systems including custom made to cover light duty and heavy duty applications.