Air Pollution! This is the most common topic about which is the whole world is discussing. Yes, there are many sources of air pollution and climate change but the toxic gas emission from the vehicles is the vital source than anything else. So smog check or emission test is very much important to prevent the air from highly polluted and hence maintaining a sustainable environment. So know here everything about this test like—how smog test happens and how often you should take your car for the test?