The emissions check program is aimed at carbon monoxide, nitrogen oxides, volatile organic compounds, and particulate pollution. Properly functioning emissions systems ensure a vehicle operates efficiently, but the effect on a car or truck's overall greenhouse gas emissions is fairly small - and it is greenhouse gases (primarily carbon dioxide) that are driving climate change.

Vehicles are still the largest source of carbon pollution in Washington. We are working to change that by making sure new cars are more efficient than old ones, supporting zero-emission vehicles and cleaner fuels, and advancing transit, ridesharing and other alternatives to single occupancy vehicles.

we expect air quality to continue to improve as older vehicles are replaced with newer, cleaner cars. Ecology will continue to monitor air quality conditions throughout Washington. If we see any reasons for concern, we will certainly take action.