- travelpaLv 710 years agoFavorite Answer
The largest part of most combustion gases is nitrogen (N2), water vapor (H2O) (except with pure-carbon fuels), and carbon dioxide (CO2) (except for fuels without carbon); these are not toxic or noxious (although carbon dioxide is a greenhouse gas that contributes to global warming). A relatively small part of it is undesirable noxious or toxic substances, such as carbon monoxide (CO), hydrocarbons, nitrogen oxides (NOx), Ozone (O3), partly unburnt fuel, and particulate matter.
Catalytic Converters - A catalytic converter is what makes emissions that much less harmful to people and the environment. As the heart of an exhaust system, it connects the exhaust manifold to the muffler. It's a contained area that encourages a chemical change; in fact, its where carbon monoxide (CO) becomes carbon dioxide (CO2) and hydrocarbons (HC) become carbon dioxide (CO2) and water (H20). In a three-way converter, nitrogen oxides (NOx) become nitrogen (N) and oxygen (O).