How Long Does A Smog Check Take (And Why)

Exact Answer: 20 Minutes To 30 Minutes

A smog test or also known as the emission test is generally performed on a car in order to know the emissions of the car.

Smog tests are generally performed in countries or cities which are heavily polluted and populated as well. Currently, smog tests are performed in about 33 cities of the United States.

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How Long Does A Smog Check Take?

Type Of Smog TestsTime
On-board diagnostic inspection10 minutes to 15 minutes
Acceleration simulation mode test15 minutes to 20 minutes
Two-speed idle test20 minutes to 25 minutes

A smog test or an emission test only takes about a minimum of 20 minutes to a maximum of 30 minutes to get completed on average. This whole process includes not just testing the emission of the car, but the paperwork process and the certification of the car as well. But, it is important to put under consideration that are could be various types of smog tests depending upon the way they are performed.

Depending upon what type of among test or the emission test is being performed on the car, the time it would generally take to complete the smog test can depend. There are majorly three types of smog tests that are performed on the car. These three types of smog tests are:

  1. (OBD) On-Board Diagnostic inspection
  2. (ASM) Acceleration Simulation Mode test
  3. (TSI) Two-Speed Idle test

The on-board diagnostic inspection gives reports if the other functions of the system are working smoothly or not. Since the onboard diagnostic inspection is a digital process, it does not take a longer time to get completed. On average, it takes about 10 minutes to 15 minutes for the process to get completed. The acceleration simulation mode test takes about a minimum of 15 minutes to a maximum of 20 minutes on average. The third test, which is the two-speed idle test takes about 20 to 25 minutes to be completed.

Why Does A Smog Check Take That Long?

Smog checks are generally done after a span of 2 years since the time the last emission test of the car was one in almost all of the cities of the unites states. However, this time duration can vary depending upon many factors. Some of the major determining factors could be the original registered place of the car, the model of the car, and the age of the car as well.

An on-board diagnostic inspection is the most common procedure used to perform a smog test and is in fact the most convenient method as well. This procedure is more of a digital process in which system software is used to read and inspect data from the person’s car computer system. If the software detects any fault in the engine system then it showcases that in the results.

The second type of smog test is the acceleration simulation mode test in which a dynamometer and a tailpipe sensor are used to test the emission system of the car. The dynamometer simulates the driving conditions of the car, even when the car is just being at one place. While, on the other hand, the tailpipe sensor checks for emission levels of the car while it is being driven. The acceleration simulation mode test takes about a minimum of 15 minutes to a maximum of 20 minutes on average.

The third type of smog test is the two-speed idle test in which the engine of the car is idled at high speed and then low speed. During this, the emissions of the car are tested by the testing devices.

A smog test tests emission levels of the car of majorly these gases:

  • Carbon dioxide
  • Carbon monoxide
  • Nitrogen oxides
  • Hydrocarbon gases

Conclusion

On average, a smog test or an emission test takes about 20 to 30 minutes. However, the time can be extended if your car fails the emission test. There are many certain reasons why a car would fail the smog test, such as if the gas cap is not properly sealed or there is some defect in the ignition system or the air filter is dirty or the catalytic converter is not working efficiently or other such reasons.

References

  1. https://www.jstor.org/stable/20053062
  2. https://www.tandfonline.com/doi/abs/10.1080/1073161X.1993.10467226
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