Unless you give it a source of ignition, it will not ignite. Now for those morons who leave their engines running while fueling, the engine draws in air for combustion and if you have a gas tank open to atmosphere ( depending on weather conditions,wind and temp) the gas fumes will eventually make it to the engine and ignite if the hot exhaust doesn't spark it first. You need to have the correct air/gas mixture for it to ignite. There is a range that will be too lean or too rich but if you find that sweet spot, kiss you butt goodbye. Pray you die because you do not want to live through 3d degree or worse burns over 90 % of your body. Also, for those regions that get cold weather static from you sliding you butt off the seat discharges at the first thing you touch causing an electrical arch. If you don't discharge first by placing one hand on the vehicle you will discharge at the gas cap and could possibly ignite the fuel vapors.
