[ACMAir]

What gases is car exhaust composed of?

[Ak]

a similar question was asked on this site: http://www.madsci.org/posts/archives/1997-12/879964012.Bc.r.html

[jorawen]

Carbon dioxide (CO2): This is a greenhouse gas and the primary component of car exhaust, resulting from the combustion of carbon-containing fuels like gasoline and diesel.

Carbon monoxide (CO): A colorless and odorless gas that is toxic to humans and animals. It is formed when carbon in the fuel does not burn completely, often due to incomplete combustion.

Nitrogen oxides (NOx): This is a collective term for nitrogen dioxide (NO2) and nitric oxide (NO). These gases are produced when nitrogen in the air reacts with oxygen at the high temperatures and pressures inside the engine's combustion chamber. They contribute to smog formation and can cause respiratory issues.

Hydrocarbons (HC): These are unburned or partially burned fuel components. Hydrocarbons are a major contributor to the formation of ground-level ozone and smog.

Particulate matter (PM): These are tiny particles of soot and other substances that are suspended in the exhaust gases. Particulate matter can be harmful when inhaled and is associated with respiratory and cardiovascular problems.

Sulfur dioxide (SO2): If the fuel being used contains sulfur compounds, the combustion process can produce sulfur dioxide. However, many countries have reduced the sulfur content in fuels to mitigate this emission.

Water vapor (H2O): This is a natural byproduct of the combustion process, as the hydrogen in the fuel combines with oxygen to form water vapor.

[Corribus]

In addition to soot, particulate matter often includes a high concentration of heavy metals. These have been greatly reduced since the early years due to, e.g., the elimination of certain fuel additives (like tetra-ethyl lead) but even so, mechanical wear of internal parts, which are largely metallic, and low-level contamination in fuels leads to inevitable release of transition metal pollution to the environment, particularly in urban areas.

https://www.sciencedirect.com/science/article/pii/0143148X84900351