Hazardous Emission of Vehicles
It is true that vehicles bring us a lot of convenience, but in the other hand they also bring a lot of hazardous factors, such as traffic accident which can kill the users or the third parties, and emission gases from the vehicles. Emission gas has a wider meaning than the exhaust emission including every kind of gases emitted from a vehicle. These can be described as the picture below.
The biggest portion from these type of vehicle emission is the exhaust emission which comes from the combustion chamber of an internal combustion engine. Notorious part of the exhaust emission is HC (Hydrocarbon), CO (Carbon monoxide) and NOx (Nitrogen Oxide), these three are the most hazardous components of exhaust emission and I will explain more in detail in the later chapter.
The next biggest portion is probably evaporative emission from the fuel. Because the fuel has very high volatility, this evaporates quite quickly in the air. The vehicle powered by internal combustion engine has to have fuel tank all the time and this fuel in the tank will evaporate from the heat which generates by engine operation of the heat from the environment, such as, sunlight.
This evaporative emission is being gathered in a carbon canister and during the engine operation this gas will be guided into combustion chamber through intake system. The canister purge valve is controlled by ECU (engine control unit). This gas is emitted from the three cases, 1) during the operation of vehicle (running loss vapors emission) 2) during high temperature phase after driving phase (Hot soal vapors emission) 3) during parking phase (diurnal vapors emission). The next case of this gas emission is the fuel gas during refueling with opened tank cap. The last source is the nothing to do with fuel but the chemical substance which was on and in the vehicle, such as paint on the vehicle body, interior material in the cabin.
At the next chapter I will explain the chemical components of this emission gases and the way of control more in detail with some regulatory information from each government.