Exhaust and harmful emissions
Exhaust emissions are the non-useable gaseous waste products produced during the combustion process. “Exhaust gas” is the standard term used to describe the waste gas from internal combustion engines.
In addition to harmless products such as water vapour, carbon dioxide and nitrogen, engine exhaust also contains pollutants which are harmful to man and the environment: carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxide (NOx).
Harmful emissions only represent a very small share of the overall emissions of a modern engine. Only 1.1 % for the petrol engine and
0.2 % for the diesel engine. The majority of exhaust consists of nitrogen, water and carbon dioxide.
However, it is important that the comparatively small quantity of harmful emissions is also rendered harmless. In order to significantly reduce these harmful emissions, the three-way catalytic converter was introduced.
Carbon monoxide (CO)
Carbon monoxide is a colourless, odourless and tasteless gas. The compound, consisting of carbon and oxygen, is formed during incomplete combustion of carbon-containing substances and is very poisonous to the respiratory system. As soon as it is inhaled and enters the bloodstream it prevents the bonding of oxygen to the red corpuscles. A concentration of 1.28 percent carbon monoxide in the air will cause death from suffocation within 1 to 2 minutes.
Since carbon monoxide is heavier than air, it accumulates especially near the ground. In addition, higher concentrations can occur in parking garages. They are usually equipped with special sensors which measure the CO content of the air.
Cold-like symptoms can result from small concentrations of 70 to 100 ppm (parts per million) in the air. 150 to 300 ppm cause nausea, dizziness and vomiting. Concentrations of
400 ppm or more result in unconsciousness, brain damage and even death. Healthy adults can withstand up to 50 ppm over an extended period; however, children and people with poor health can already experience problems at this concentration.
Hydrocarbons are chemical compounds which consist only of carbon (C) and hydrogen (H). They can be found in large quantities in crude oil, natural gas and coal, where they are the actual “fuel”. Some hydrocarbon compounds cause cancer.
When exposed to sunlight, hydrocarbons and nitrogen oxide react to form ozone. In the lower layers of the atmosphere this is a hazardous substance, which irritates the mucous membranes and causes headaches and nausea. Since 1995, ozone is also considered to be a “proven cancer-causing agent”. In addition, increased concentrations of ozone in the air can damage vegetation severely.
Nitrogen oxide (NOx)
Nitrogen oxides are the gaseous oxides of nitrogen (N). They are abbreviated NOx because of the various possible compounds with different numbers of atoms: N2O, NO, N2O3, NO2, etc.
If they come into contact with water (also in the form of fog), acids are formed, which irritate the mucous membranes and can even cause lung damage. There is one exception: Nitrogen monoxide (N2O), also known as “laughing gas”. However, this is a greenhouse gas, which damages the protective ozone layer in the upper atmosphere.