I'm need some technical clarification on the subject of Methane LEL & UEL. We curently are supplied personal monitors calibrated with Methane, the reference explosive limit they use for setting the lower and upper alarm is 5% - 15%. We have recently had it suggested this may not be correct and that the correct range is 4.4% - 17%. A number of training provider who train in authorised gas testing have also confirmed they reference 5% - 15% which aligns to what our gas monitor provider uses. Fortunately our alarm setting are 10% and 20% the LEL therefor not an immediate concern. I would though like verification of what is recognised as the explosive range. Would appreciate guidance on what reference material I can use for verification.

BS EN 60079-20:1 2010 Explosive Atmospheres. Material characteristics for gas and vapour classification - Test methods and data Gives the following for methane, Annex B tables Melting Point -182*C Boiling Point -162*C LFL 4.4% (% vol) UFL 17% Autoignition 600*C ATEX temp rating T1 Equipment Group IIA This standard is still valid. The BS EN60079 series of standards are the bible for ATEX/DSEAR.