Exhaust emissions from diesel engines mainly produce the following substances:
1. Carbon monoxide (CO for short): a gas produced by the combustion of fuel in the absence of oxygen.
2. Hydrocarbons (HC for short): a general term for compounds formed by carbon and hydrogen. It refers to the carbon and hydrogen compounds, fuel vapor, etc. generated by the unburned fuel or lubricating oil in the cylinder or by decomposition.
3. Oxides of nitrogen (NOx for short): the gas formed by the oxidation of nitrogen in the cylinder at high temperature, which is mainly composed of nitric oxide and nitrogen dioxide.
4. Particulate matter (PM): the general term for various solid particles in the exhaust, usually including heavy metal compounds, sulfates, soot particles of sof soluble organic matter, and liquid particles wrapped with fuel oil.