Some side effects of inhaling sewage gas are dizziness, nausea, headache and loss of consciousness, as stated by the Wisconsin Department of Health Services. The National Association of Certified Home Inspectors, or InterNACHI, states that sewage gas is composed of methane, hydrogen sulfide, carbon dioxide, ammonia and sulfur oxide.
The Wisconsin Department of Health Services notes that two of the most detrimental components of sewage gas are hydrogen sulfide and ammonia. Hydrogen sulfide is colorless, flammable, highly toxic and has the unmistakable odor of rotten eggs, as defined by the Agency for Toxic Substances and Disease Registry. It is produced naturally by decaying organic matter, and can enter the home in a number of different ways. The Wisconsin Department of Health Services warns that floor drains, leaky or blocked plumbing roof vents or foundation cracks might release the harmful gas into a person's home.
Since sewage gas is odorless, residents of a home may not be aware they are exposed to the substance. Therefore, it is important to know some of the signs and symptoms of exposure. InterNACHI states that hydrogen sulfide poisoning can cause eye irritation and damage as well as nervousness, pulmonary edema and, in extreme cases, even death. In addition to the negative health impact of sewage gas, there is a very real threat to the home. Because methane and hydrogen sulfide are highly flammable, there is a risk of explosion if the levels are highly concentrated.