I thought methane was odorless & colorless. That's why they needed the canary in the coal mine. While looking it up, I came across this in a coal mining related site.... A "black damp" is a mix of carbon dioxide and nitrogen caused by corrosion, a process that can cause suffocation by drawing the oxygen from the air. An "after damp" includes the same gases as a black damp, plus carbon monoxide, and usually forms after a mine explosion. A "fire damp" is particularly dangerous, because it consists mainly of methane, a flammable gas. A "stink damp," which reeks of rotten eggs, is mostly hydrogen sulfide. This gas, too, can explode. A "white damp" is any air containing carbon monoxide, a gas that has no discernable scent but is toxic in even low concentrations. On occasion, I am a source of toxic gas in enclosed spaces (my Carharts)....it sometimes has me wondering if I'm getting out alive.