The harmful substances emitted by vehicle engines are:
Unburned hydrocarbons (HC)
The unburned hydrocarbons are a result of incomplete combustion of fuel or escaping from the oil pan (sump) of the engine . These are hydrocarbons aldehyde, cyclic paraffinic extended chain aromatic and which are able to combine with oxygen. Laboratory studies have shown that these compounds react in the presence of ultraviolet radiation and irritate human eyes , pollute the atmosphere and cause negative effects on vegetation . They are still responsible for photochemical smog and some of them (particularly benzene) is carcinogenic .
Oxides of nitrogen (NOx)
It is one of the key players in the creation of photochemical smog . Nitrogen oxides under the influence of solar radiation are involved in chemical reactions that result in the conversion of unburned hydrocarbons into photochemical oxidants, and the production of ozone, which is also toxic to the respiratory system. With the aid of ozone and oxygen in the atmosphere , the nitrogen oxides then creates a cycle of secondary pollution, which under suitable weather conditions results in the formation of photochemical smog .
Carbon monoxide (CO)
Carbon monoxide comes mainly from gasoline. It is essential product of incomplete combustion of hydrocarbons and when its concentration in air exceeds some levels causes headaches and problems in the circulatory system. At very high concentrations (which may exist but only indoors) can be fatal . The CO, however, is unstable compound and when found in the open air quite quickly is converted into harmless carbon dioxide and so it has only a local effect.
Smoke
Smoke comes mainly from diesel. Due to the usual visible hue of diesel engine exhaust in practice the distinguish of so-called smoke exhaust emissions of the following three categories depending on the shade of:
- White Smoke, consisting of fog liquid unburnt fuel particles that occurs during cold start.
- Blue Smoke , consisting of fog liquid unburned particles of lubricating oil, that occurs when there is a problem with lubrication (eg worn or stuck piston rings)
- Black smoke or smoke "Soot type" consisting essentially of solid fine particles of unburned carbon, which is the soot generated by the pyrolysis of the fuel locally in areas with a relative deficiency of oxygen appearing in the region of high loads (e.g. example, > 85 % of maximum).
