Before implementing wireless transmitters in hazardous areas, it is necessary to define the area. Instrumentation commonly used in factory automation and the process industries typically requires adherence to UL Class I, Div. 1 or 2. For areas where ignitable substances such as gases, vapors, or liquids are likely to exist only under abnormal conditions, as classified under Class I, Div. 2, instrumentation rated for the area should not require an explosion-proof housing.
For areas where these substances can exist under normal conditions, as classified under Class I, Div. 1. instrumentation must be either contained within a suitable explosion-proof housing, contained within a suitable purged housing, or rated as intrinsically safe.