NF C23-560-2:2005 Electrical apparatus for the detection and measurement of flammable gases - Part 2 : performance requirements for group I apparatus indicating a volume fraction up to 5 % methane in air.
2008NF C23-579-29-1:2008 Explosive atmospheres - Part 29-1 : gas detectors - Performance requirements of detectors for flammable gases.
2005NF C23-560-2:2005 Electrical apparatus for the detection and measurement of flammable gases - Part 2 : performance requirements for group I apparatus indicating a volume fraction up to 5 % methane in air.