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How Long Does A Smog Check Take?

Last updated 03/14/2024 by

Lacey Stark

Edited by

Fact checked by

A smog check, also known as a vehicle emissions test, should only take about 10 to 20 minutes to complete. However, that can vary by the type and age of car you have, the testing equipment used, and the state you live in. The purpose of smog certification is to improve the air we breathe by reducing the amount of pollutants in the air caused by unhealthy emissions from the vehicles we drive every day.
You might wonder why sometimes the Department of Motor Vehicles sends you a registration renewal notice stating that you need to get a smog check or emissions test before you can get a new sticker for your car. Depending on the state you live in, on-road gasoline-powered vehicles manufactured after 1975 must meet certain emissions standards.
If you don’t meet those standards, meaning you fail the smog check, you will not be able to register your motor vehicle until you have made the necessary repairs. After that, you need to return to the smog station and pass a new test. Let’s explore why you might need a smog inspection, how they test for emissions standards, and what might cause smog test failures.

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Why do many states require a smog check?

In 1990, the Federal Clean Air Act was amended in an attempt to substantially reduce pollutants in the air that are unhealthy. As a result of that, the Environmental Protection Agency (EPA) came up with standards to help reduce the amount of harmful pollutants emitted into the air by motor vehicles. Exceptions to this include electric and antique cars, other vehicles built before 1975, and some diesel-powered vehicles.
That’s why you can’t get your car registered without passing a smog test. This is a good thing. Less pollution equals better air quality.
And the path to cleaner air also depends on cooperation and collaboration between the EPA and vehicle, engine, and fuel manufacturers; state and local governments; transportation planners; and you as drivers. According to the EPA, this integrated approach to vehicle emission control is responsible for helping to reduce air pollutants emitted from cars during the last 30 years.

Do all states require a smog check?

As of 2022, more than 30 states mandate a smog check to reduce air pollution in at least certain areas. A lot of states don’t require an emissions test at all, but a handful of states have mandatory smog-check testing. Others only require a smog check in certain areas, such as in or near big cities.
Use the table below to determine whether you’ll need to complete a smog check before receiving your vehicle’s registration.
StateSmog test required?
AlaskaRequired for cities, such as Anchorage
ArizonaRequired in Phoenix and Tucson
ArkansasNo, but encourages voluntary testing
ConnecticutRequired for commercial vehicles
District of ColumbiaYes
FloridaNo longer required
GeorgiaRequired for cars between 4 and 24 years old
IdahoNo, but testing available in Ada and Canyon counties
IllinoisRequired in Chicago and East St. Louis areas
IndianaRequired biennially in Lake and Porter counties
MaineRequired for Cumberland County
MarylandRequired for 13 counties and Baltimore City
MassachusettsRequired for vehicles less than 15 years old
MissouriRequired for St. Louis metropolitan area
NevadaRequired for vehicles newer than 1968 in Clark and Washoe counties and Las Vegas and Reno areas
New HampshireRequired for vehicles less than 20 years old
New JerseyRequired biennially
New MexicoRequired for vehicles in Bernalillo County
New YorkRequired for vehicles built after 1996
North CarolinaRequired in 22 counties
North DakotaNo
OhioRequired in Northeast Ohio, around Cleveland
OregonRequired in Portland and Medford areas
PennsylvaniaRequired in metropolitan areas
Rhode IslandRequired biennially
South CarolinaNo
South DakotaNo
TexasRequired in 17 counties
UtahRequired in Cache, Davis, Salt Lake, Utah, and Weber counties
VirginiaRequired biennially
WashingtonRequired for cars with model years after 2009 to clear California emissions standards
West VirginiaNo
WisconsinRequired for Kenosha, Milwaukee, Ozaukee, Raine, Sheboygan, Washington, and Waukesha counties
Source: Kelly Blue Book

Pro Tip

To avoid a long wait at the smog check facility, try to go at off-peak times. Most states that require the test order it every two years as a contingency to getting your yearly registration sticker. That means there are plenty of others in your position. A Saturday afternoon is probably a terrible idea, but a Tuesday at 3:00 p.m. might get you in and out pretty quickly.

What is a smog test?

As mentioned previously, the purpose of a smog check is to ensure that your vehicle isn’t emitting harmful chemicals and elements into the environment.
The pollutants smog check stations look for include:
  • Carbon monoxide
  • Carbon dioxide
  • Hydrocarbons
  • Oxides of nitrogen
  • And other tailpipe emissions

Smog test systems

Depending on your state and your type of vehicle and model year, there are a few different methods of testing your car for acceptable emission levels. A smog check should include both a visual inspection of the emission control systems and equipment plus a physical computerized instrument inspection.
The following are the three most common testing procedures.
  • On-board diagnostic inspection (OBD). This method is typically used for cars manufactured from 1996 and up. The smog inspector will plug their state-certified device into your on-board computer diagnostics system and monitor the emissions levels from your exhaust. If all is well after completing the smog check, you’ll be on your way. On the other hand, if something is amiss, the OBD will throw out a fault code and you will need to have the issue diagnosed and repaired.
  • Acceleration simulation mode test (ASM). Most cars made before 1996 don’t have an on-board diagnostic system, so the technician will use what’s called a dynamometer. The dynamometer acts as a driving simulator while a sensor is placed in the exhaust pipe to detect pollutant levels.
  • Two-tier idle test (TTI). This test is meant for cars manufactured between 1976 and 1995 because they have variable idling and timing. The procedure tests exhaust emissions at both higher and lower speeds.
If your car fails the emissions test, you may need to make some significant repairs. Depending on how extensive the repairs are, you may be better off taking out a personal loan to pay for the work. Fortunately, you can compare your options for personal loans below to get a better idea of what loan terms you qualify for.

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How long does a smog check take?

As mentioned, a smog check typically takes only 10 to 20 minutes to complete, after which you should be on your merry way. However, if you fail, the inspectors may be able to tell you what the problem is — or at least give you an educated guess.
If your vehicle passes, you will be given a smog certificate or vehicle inspection report showing you’re good to go. That information will be sent directly to the DMV, Secretary of State, or whoever manages motor vehicles in your state government, and you’re then free to register your car.
Oftentimes, you can get your vehicle sticker right at the testing facility, also known as the smog station. This can be especially convenient if you happened to wait until the last minute. Regardless, you will pay a small “convenience fee” for the privilege, but it could be well worth it to have your smog certification and car registration taken care of all at once while on your lunch break.

Why would a vehicle fail a smog test?

There are a number of reasons why your car might not pass a smog check. Many of them are quick, inexpensive, and easy problems to solve. But sometimes it could signal a larger problem with your vehicle, such as an issue with your EGR valve (exhaust gas recirculation system). Here are a few other common problems that could cause a vehicle to fail at a smog station.

Gas cap failure (or loss)

Admit it, you (or a friend) might have lost a gas cap at one time or another. If so, that can cause your vehicle’s check engine light to come on, in addition to a failed smog test. A gas cap is part of the emission control system and it helps to seal in evaporation and fuel vapors.
If the cap is missing, has a deteriorated seal, or even isn’t closed properly, it will send a message to the computer in your car that there’s a problem, and you won’t pass the smog check. Luckily, this is one of those easy fixes. All you have to do is go to your local auto parts store and buy a new cap. Be sure to get the right one for your car’s make and model year.

Fuel evaporative system

The fuel evaporative system, sometimes called the evaporative emission control system or EVAP, works alongside your gas cap and should prevent gas vapors from being released into the air. This could be a red flag and should be diagnosed by a certified mechanic as it might signal a bigger issue.

Dirty air filter

If your air filter is dirty and clogged with debris, it upsets the precise balance of fuel and air needed. This restricts your engine’s air intake system and could cause further issues. This is another easy and inexpensive hitch that might very well fix your smog check problem.

Ignition system

A defective ignition system is usually caused by old or bad spark plugs or wires. If your ignition system is defective it doesn’t efficiently burn fuel, so it releases hydrocarbons into the air. This is a more expensive fix than a gas cap or filter, but not ridiculously so.

Faulty catalytic converter

A catalytic converter is a very important part of the emission control system in your car. It converts the hydrocarbons, carbon monoxide, and nitrogen oxide released by the engine into carbon dioxide and water. Any issue with the catalytic converter could lead to a smog test failure, and they’re not cheap to fix.

Pro Tip

If you’re due for a smog check and your check engine light is on, you’re pretty much guaranteed to fail your emissions test. But, before you go and pay a mechanic to diagnose the problem, go to the smog check first. They might be able to tell you on the spot what the problem is, potentially saving you some money.


Should I drive my car around before a smog check?

If everything seems fine with your car, there is no need to drive your car around before going in for a smog inspection. However, if you’ve failed the smog certification process but had the repairs made, you may need to drive around for a while (about 50 to 100 miles), until your vehicle’s check engine light has turned off. If the light is still on, you might fail the smog tests again.

How much does a smog check cost in California?

Smog check certification costs are not regulated by the state of California, so prices will vary by smog check stations. In cases where your car is eight years old or younger, however, drivers are not required to get smog checks until the ninth year. Instead, you will have to pay an annual smog abatement fee. This comes along with your DMV registration renewal notice and costs $25 a year.
As a side note, many state emissions tests and smog check stations are free, but you will need to check with your individual state regulations for further details.

Key Takeaways

  • An official smog inspection shouldn’t take much longer than 20 minutes, give or take.
  • In most states that require smog certifications, you won’t be able to register your car until you have passed the smog check or had repairs made by a certified technician if you experience smog check failure.
  • There are three common ways to test for vehicle emissions depending on the model year of your car.
  • Oftentimes, a smog test failure is due to easy fixes, such as a dirty air filter or faulty gas cap. Other times you might need more serious repairs before you can get a clean smog certification or vehicle inspection report.
  • Technological advances in vehicle and engine design — together with cleaner, higher-quality fuels — have helped to drastically reduce emissions from motor vehicles.

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