Emissions Testing: What, Where and How?

China, Smog

China issued its first ever national Smog Red Alert this week.

Recently, while many of us were simultaneously celebrating the holidays and hiding from in-laws, something alarming happened in China. Across 24 major Chinese cities, housing roughly 200 million citizens, a smog ‘Red Alert’ was issued. While there has never been any question as to the growing threat of air pollution in the country, this elevated alert is indicative of how significant the problem has become in certain corners of the world. When a smog alert, such as the one issued Christmas day, is ordered, people are expected to remain indoors, ultimately leading to a sharp downturn in the productivity of the economy as a whole. Government officials have declared a ‘war on pollution,’ though many local skeptics say new laws don’t do enough to combat the increasingly thick haze that blankets the sky.

Los Angeles, California

Los Angeles, California skyline.

Admittedly, America has its own set of issues in regards to environmental concerns, largely in California, where childhood asthma rates are as high as 14 percent in the smoggiest areas. In 1970, amid growing concern about environmental pollution, the EPA was established in an effort to consolidate federal research, monitoring, standard-setting and enforcement activities relating to environmental protection into a singular 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. This allowed private citizens to hold government agencies accountable for not following regulations. 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 emissions. These programs are an important part of the effort to improve the air we breathe.

Curious as to what is expected of you in your state?  Let’s break it down.

States Requiring Periodic Vehicle Emissions Inspections

In defining what is deemed an acceptable level of pollution from a vehicle, each state possesses its own unique standards and processes. 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 it became possible to build cleaner, more efficient engines. Most new vehicles are also exempt from testing, as manufacturers are now inherently required to meet current standards.

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.


  • Frequency: Upon receiving your vehicle registration renewal application, the form will indicate whether or not an emissions test is required.


  • Frequency: Required every two years, or if you are selling a vehicle older than four years.


  • Frequency: Vehicles from 1981 or prior require a yearly emissions test. Vehicles from 1982 and on require a test every two years.


  • Frequency: Notification of required testing is sent at least 45 days in advance of due date.


  • Frequency: Required every two years before you are able to renew your vehicle registration. Renewal notices are sent approximately 90 days prior to registration expiration.


  • Frequency: Yearly, but only in these specific counties: Cherokee, Clayton, Cobb, Coweta, DeKalb, Douglas, Fayette, Forsyth, Fulton, Gwinnett, Henry, Paulding, or Rockdale County.


  • Frequency: Every two years, but only in Ada County, Canyon County, and the city of Kuna


  • Frequency: Every two years


  • Frequency: Every two years for vehicles from 1976 or newer.


  • Frequency: Every two years for vehicles from 1996 or newer (non-gasoline fueled cars are exempt)


  • Frequency: Annually, but only for residents of Cumberland County


  • Frequency: Every two years


  • Frequency: Annually


  • Frequency: Every other year, based on the model year of the vehicle


  • Frequency: Annually

New Hampshire

  • Frequency: Annually

New Jersey

  • Frequency: Every two years

New Mexico

  • Frequency: Every two years and at change of ownership

New York

  • Frequency: Annually

North Carolina

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


  • Frequency: Every two years


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


  • Frequency: Annually

Rhode Island

  • Frequency: Annually


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


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


  • Frequency: Every two years for vehicles less than six years old, annually for vehicles older than six years


  • Frequency: Annually


  • Frequency: Every two years


  • Frequency: Every two years.

West Virginia

  • Frequency: Annually


  • Frequency: Annually for vehicles newer than 1996 in the following counties: Racine, Washington, Kenosha, Sheboygan, Milwaukee, Waukesha, Ozaukee

Exhaust Pipes

Failing an Emissions Test – Next Steps

If you reside in a state requiring vehicle emissions test and fail to meet the specified requirements, you cannot register your vehicle. In essence, this means you are no longer allowed to drive until the situation is handled. Upon failure, you will receive a report from the inspection station detailing all required repairs necessary. You will want to hold onto this report and provide it to the car repair shop in an effort to avoid any confusion on what specifically needs to be fixed. Once the vehicle has been repaired, you will need to bring it back to an inspection station for a re-test. It is vital to take care of this as soon as possible to avoid letting your license plates expire while seeing to repairs.

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. As always, regular vehicle maintenance can help in avoiding mechanical issues that could lead to failing the emissions test, so be sure to practice good vehicle ownership tactics. There are a few specific items to look out for, as they are the most common causes of a failed emissions test:

  • Out-of-spec fuel metering – caused by the vehicle CPU or the fuel injection and carburetor unit.
  • Worn-out spark plugs
  • Vacuum leaks – Caused by faulty hoses or a dysfunctional MAP sensor
  • Air-Injection and EVAP malfunction – Removes ability to control the carbon monoxide and hydrocarbon emissions properly.

Tips to Maintain a Passing Grade

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

  • Change your engine oil regularly – Dirty oils can result in higher than normal emissions levels.
  • Use Vehicle-Appropriate fuel additives – Helps in purging carbon deposits from the engine during normal operations
  • 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 engines ability to process hydrocarbons and CO emissions.
  • Find a hybrid or electric car on Carsforsale.com.

Does your car make the grade? Let us know in the comments!