Air pollution is one of the biggest challenges modern societies have to face. Thankfully, more and more effort is put into limiting smog-causing fumes emissions. In California, for example, each vehicle must undergo biennial smog checks and companies like Clean Air Smog are here to make the whole process fast and easy. To get the work done, the amount and type of pollutants released are confronted against the state's standards. When everything stays within permissible limits, the driver receives a certification stating that the vehicle is ready to hit the road again.