Methane gas is odorless and colorless, non-toxic and non-carcinogenic. It is an inert gas. Methane gas is lighter than air, approximately 55% the weight of air. The ignition temperature of methane gas is approximately 1,000¢ªF, or a spark. Methane gas can only combust within a specific range of concentrations in air. The explosive range limits are typically identified as the ‘LEL’ and the ‘UEL’ of methane gas. The ‘LEL’ or Lower Explosive Limit of methane gas is 50,000 ppmv, any concentrations less than this are too lean to combust. While the ‘UEL’ or Upper Explosive Limit is 150,000 ppmv, any concentrations greater than this and there is not enough oxygen in the air for the methane to combust. When methane gas combusts in an open space it burns and when it combusts in an enclosed space it explodes.