Describes performance requirements for Group II (as defined in European Standard EN 50054) portable, transportable and fixed apparatus for detection and measurement of combustible gas or vapour concentrations with air. The apparatus, or parts thereof, may be used in potentially explosive atmospheres, other than mines susceptible to firedamp (ie. Group I). General requirements and test methods applicable to apparatus covered by this European Standard are given in EN 50054. Limited to apparatus intended for detection and measurement of combustible gas or vapour concentrations with air up to 100% lower explosive limit (LEL).