Emissions Testing: Everything You Need to Know

Hazy Days Ahead

Government officials across the world have declared a ‘war on pollution’ over the last decade. With much of the population on the road every day, the air quality in the biggest U.S. cities is hurting. With consistent pollution warnings across cities like Los Angeles, Phoenix, Pittsburgh, and Salt Lake City, political officials and citizens alike support automotive regulations.

Though skeptics say these laws don’t do enough to combat the thick haze that blankets the sky, cities across the country are continuing with emissions testing to combat car exhaust pollution. But what exactly does this mean for drivers? How is it helping our already polluted cities, and how do we get our emissions tested?

Cities across the country are continuing with emissions testing to combat car exhaust pollution. Click To Tweet
Los Angeles, California
Los Angeles, California skyline

Emissions in America

In 1970, amid growing concern about environmental pollution, the EPA was established in order to consolidate federal research, monitoring, standard-setting and enforcement activities relating to environmental protection into a one agency. Part of the EPA’s job is to enforce the Clean Air Act of 1963, which was the first major environmental law in the United States to include a provision for citizen suits. The act mandated air quality control regions and designated them as attainment vs. non-attainment, where non-attainment meant an area did not meet national air quality standards. As a result, environmental standards and required vehicle certifications vary from state to state. Sometimes called a smog check, smog test, or an emissions test, the main goal is to test the vehicle and engine’s emissions. These programs are an important part in the effort to improve the air we breathe.

Cars on I-25 with exhaust fumes
Denver, Colorado

Not sure if your state requires vehicle emissions testing? Here are the states that require you to have your vehicle tested. Be sure to check for any exemptions if your state is on the list.

States Requiring Periodic Vehicle Emissions Testing

Each state possesses its own unique standards and processes for emissions testing. There are multiple states where these regulations apply only to the most densely populated urban areas. Missouri, for example, only requires emissions inspections for those living in the St. Louis Metropolitan Area. This pattern of exemption also pertains to certain vehicle classes. Antique vehicles are not required to pass an emissions test, as they were built before cleaner, more efficient engines were made. Most new vehicles are also exempt from testing, as manufacturers are now inherently required to meet current standards before pushing out a new model.

Be sure to check with your state’s emissions testing facilities if you’ve moved recently to ensure your vehicle is ready for inspection.

map of states in the United States with emissions requirements

The list below is subject to change at any time. Emissions regulations shift frequently. The best source for information regarding your specific testing requirements will be from your state’s DMV or DOT website.


  • Annually or every two years, depending on vehicle make and model


  • Every two years
  • Six counties are exempt


  • Every two years
  • Last seven year models are exempt


  • Every two years


  • Every two years


  • Annually in 13 counties


  • Annually
  • Only citizens of Ada and Canyon counties, and the city of Kuna


  • Every two years


  • Lake and Porter counties only
  • Every two years


  • Every two years


  • Annually
  • Take note that Maine does not allow any extensions or waivers for emissions testing


  • Every two years


  • Annually


  • Annually


  • Annually

New Hampshire

  • Annually

New Jersey

  • Every two years

New Mexico

  • Annually

New York

  • Annually

North Carolina

  • Annually, but only in 48 specified counties (visit NC DMV website for full list)


  • Every two years


  • Every two years for residents in the Portland and Medford areas


  • Annually

Rhode Island

  • Every two years with registration


  • Annually for residents in the following counties: Davidson, Shelby, Hamilton, Rutherford, Sumner, Williamson, Wilson


  • Annually for residents in the following areas/counties: Austin-Round Rock, Houston-Galveston-Brazoria, Dallas-Fort Worth, El Paso


  • Every two years for vehicles less than six years old
  • Annually for vehicles older than six years


  • Annually


  • Every two years


  • Every two years


  • Every two years

Note that not all states offer exemptions or waivers, but for those that do, some trucks, antique vehicles, and hybrid vehicles may be exempt. Check with your local emissions testing organization to learn more.

What Happens When You Fail an Emissions Test?

If you live in a state that requires an emissions test and fail to meet the requirements, you won’t be able to register your vehicle. This means you’re not allowed to drive until the you fix the issues discovered by the emissions test. Upon failure, you will receive a report from the inspection station detailing all repairs that are required. Hold onto this report and provide it to your mechanic to ensure everything that needs fixing is fixed. Once your vehicle has been repaired, bring it back to an inspection station to test again. Take care of this as soon as possible to avoid letting your license plates expire during this time.

Should your vehicle fail the test again, you may be eligible for a waiver. This is dependent upon the rules of your state, so be sure to research what the relevant guidelines are for your specific location.

cars driving on the freeway through thick smog

Tips to Maintain a Passing Grade

Here are some ways to help keep your vehicle within emissions standards:

  • Change your engine oil regularly: Dirty oil can result in higher than normal emissions levels.
  • Use vehicle-appropriate fuel additives: Additives help purge carbon deposits from the engine while you drive.
  • Regularly replace fuel and air filters: Dirty filters can cause high hydrocarbon output.
  • Adjust your carburetor for a balanced air-fuel mixture: If the air-fuel mixture is too lean or too rich it can lead to long-term issues in the engine’s ability to process hydrocarbons and carbon dioxide emissions.
  • Regularly maintain your vehicle: Keeping up with regular maintenance may prevent you from failing an emissions test. Good maintenance is the key to keeping your car running efficiently!
  • Keep tabs on your smog test results:You can easily check your smog test results using an OBD scanner to help you manage your expectations before heading into an emissions station.
  • Find a hybrid or electric car on Carsforsale.com.

What do you think about emissions testing? Leave us a comment below to share your tips for passing an emissions test!

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Erin Maxson

Erin loves nothing more than a good road trip. To her, getting behind the wheel is one of the biggest adventures you can take because it can lead to anywhere. Alongside her Toyota Tundra, you'll find her co-pilot pup, Rory, and a 1976 Airstream Argosy in tow. Her motto: Life is a scenic road, take your time and enjoy the ride.

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  1. Liz Hudson August 8, 2019

    It’s good to know that changing the engine oil regularly and replacing fuel filters can help keep your car within emissions standards. I can’t afford an electric car at the moment, but I want to keep my carbon footprint as low as I can. I will be sure to get my car serviced with emissions testing on a regular basis so I contribute as little to air pollution as possible.

    1. Carsforsale.com Team August 8, 2019

      That’s great Liz! We hope you found the article informative and helpful. Thanks for reading!

  2. Johnny McCarron January 6, 2020

    Ah, thank you for listing which of the different states require inspections and how frequently. I think it might be time soon for me to get my car inspected. Even if it isn’t a law, it’s still a good idea just to be sure you’re driving safely. http://www.kevinsautos.com.au

    1. Carsforsale.com Team January 6, 2020

      No problem, Johnny! We are here to help!

  3. obdstations February 8, 2020

    I will be sure to get my car serviced with emissions testing on a regular basis so I contribute as little to air pollution as possible.

    1. Carsforsale.com Team February 10, 2020

      Thanks for sharing!


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