Sewer gas is a mixture of gases forme in sewers by the decomposition of organic household or industrial wastes, as well as other gases released from this effluent. The gases from decomposition include hydrogen sulfide, ammonia (which are toxic), as well as methane, carbon dioxide, sulfur dioxide and nitrogen oxides. When substances are improperly disposed in sanitary sewers and septic systems, like paint thinner and gasoline, their very flammable fumes become transient parts of sewer gases. Sewer gases are of concern due to their odor, health effects, and potential for fueling explosions.