Most vehicles with over 20 years of age have low combustion efficiency by no catalytic converters. One of the most important ways to control and reduce emissions from vehicles is to conduct periodic technical inspection (PTI). According to the regulations of each country, the frequency of periodic technical inspection is different and is determined by the quality of air.
Materials and methods
Data of light vehicles, which had been tested in 2010, was collected from Tehran vehicle technical inspection bureau. Collected information of data on vehicles manufactured from 2004 to 2008 including Pride, Peugeot 206, Peugeot 405, Peugeot Pars, Samand and Roa. About 248865 and 236084 vehicles were studied for HC and CO emissions, respectively.
According to results one vehicle among every 6 Roa, every 14 Pride, every 22 Peugeot 405, every 40 Peugeot 206, every 125 Samand and every 111 Peugeot Pars, which were referred to technical inspection centers for first time, two years after manufacture, had higher pollutants emission compared to the permitted standards.
The results showed that if the periodic technical inspection intervals of vehicles increase from two years to more than two years, for example to five years, about 17.5 % of Peugeot 405 and 10.8 % of pride will be recorded for CO emissions higher than standard rate. Also, about 62 % of new vehicles will have higher levels of HC emissions, which can cause air pollution and an increase in the concentration of pollutants and eventually cause serious harm to public health