The power plant I work at has four 170Mw combustion turbines that are supplied with 500 psig natural gas. Periodically the fuel gas pipeline and its associated heat exchangers and filter vessels need to be depressurized for maintenance purposes. Until I intervened recently, a large volume of this gas was vented off to atmosphere in a downward direction onto people and a number of potential ignition sources such as electric carts, pickups, motor starter contactors, lighting, etc., through a 2-inch line. I know this because I was one of the people who "felt the cool breeze" of the methane on my skin one night. But I had to fight an uphill battle to modify the vent lines to vent the methane vertically. Unbelievably, workers and even management simply don't believe that a methane gas cloud will form in a relatively open area nor do they believe that it can ignite. Some even believe that the gas rises because CH4 "is lighter than air". It's not hard to find video and pictures of explosive gas accidents and disasters, but these guys can't see the connection so I'm trying to educate them with the facts so they don't blow themselves (and most importantly me) up in the process. I know that the gas cools as its pressure drops increasing its density to where it will settle into low spots as it diffuses into the atmosphere, and that a deflagration (fire ball) can easily occur, but I don't know what temperature to expect if ignition occurs in the atmosphere. Anybody got a clue?