Domestic rubbish can produce a lot of methane. The largest explosion pressure biogas is methane and carbon dioxide-based with combustible mixture of gas, mixed with air to form an explosive mixture, bringbing explosion hazard when encountering with sparks and high temperature. it is common to see such  flammable and explosive chemical materials as hydrogen, acetylene, CO, SO2, all kinds of hydrogen sulfide, fuel and coal. The innition source refers to the fire, sparks, arc, and high temperature which can make flammable materials  reach ignition. In general, the oxygen in the air acts as an oxidant role, which is said to exist everywhere.