Did you know if you own a vehicle you might be legally required to take it to a mechanic for emissions tests every two years? Although laws and regulations vary by state and city, they all work toward the same goal: reducing pollution to improve air quality and protect public health. If you’ve recently bought a car, read the information below to learn about vehicle emissions testing so you understand what is needed before setting up your first appointment.

What is a vehicle emissions test?

A vehicle emissions test helps determine the amount of air pollutants emitted from a motor vehicle’s exhaust system. The inspection identifies vehicles that have malfunctioning emissions control systems or are otherwise not meeting local pollution control regulations.1 If a vehicle emits too many pollutants, the owner will need to have the emissions system repaired before they can renew their vehicle registration.2

Why do we need vehicle emissions tests?

Established by the 1990 Clean Air Act Amendments, vehicle emissions testing helps reduce vehicle-caused air pollution. According to the U.S. Environmental Protection Agency, owners of vehicles that fail the emissions test are required to make the necessary repairs to bring them within the legal limits.3

Is testing required in all states?

Thirty-five states and territories require emissions tests.2 In those areas, testing is usually required for vehicles that meet certain criteria, including the vehicle’s age, weight, type, where it is registered, what type of fuel it uses and the type of use. The cost, vehicle emissions law, number of testing facilities, testing rules and procedures, repair assistance and retesting directions varies by location.

What happens during an emissions test?

The procedure may include an idle test to check emissions when the car is stationary and/or a high revolutions-per-minute test when it’s being driven.1 The inspector might collect a sample of the emissions, conduct an onboard diagnostics system test or simply make a visual inspection of the vehicle. The tailpipe emissions are measured for their levels of carbon dioxide, carbon monoxide, hydrocarbons and other chemicals. All vehicles undergo a gas cap pressure check to ensure that fuel vapors aren’t escaping the gas tank.1

Caring for your vehicle goes beyond emissions testing. Follow our map for preventative vehicle maintenance to stay on track.