Gas Explosions: How they Happen
Natural gas explosions occur when leaking gas accumulates in an enclosed area and ignites. Gas that combines with air above ground, below ground or in any type of conduit can form a highly volatile mixture; when the concentration of natural gas falls between 5% and 15% volume in air and an ignition source is present, an explosion can occur. (When the volume of gas in air is at least 5%, a gas meter that reads a percentage of LEL will indicate a 100% reading.)
Take all reports of gas leaks seriously, and take immediate action to identify the source of the leak and eliminate ignition hazards.