Missouri's emissions testing requirement and who must comply
Missouri requires emissions testing for most vehicles registered in the state, but the requirement depends on where you live and what you drive. The Missouri Department of Natural Resources administers the program through a network of certified testing stations. Vehicles registered in the St. Louis and Kansas City metropolitan areas must pass an emissions test every two years; vehicles in the rest of the state do not require testing.
Diesel vehicles, motorcycles, and vehicles model year 1967 or older are exempt from testing. Vehicles model year 1996 and newer in non-attainment areas (primarily St. Louis and Kansas City) must meet current federal standards. If you live outside these two metro areas, you will not encounter a state emissions requirement, though you may still need testing if you move or register your vehicle elsewhere.
New vehicle registrations in the testing areas are exempt for the first two model years after purchase. After that, testing becomes mandatory every two years on or before your registration renewal date.
Key Takeaways
- Emissions testing is required only in St. Louis and Kansas City metro areas; the rest of Missouri has no state testing requirement.
- Most gasoline vehicles must test every two years before registration renewal, while diesel vehicles and motorcycles are permanently exempt.
- You can find certified testing stations through the Missouri Department of Natural Resources website or by calling your local health department.
- A failed test means you have 30 days to repair your vehicle and retest at no additional charge at the same station.
- Testing costs vary by station but typically range from $15 to $30 per vehicle.
Where to find a certified testing station in Missouri
The Missouri Department of Natural Resources maintains a searchable database of certified emissions testing stations on its website. You can search by county or zip code to find stations near you. Most stations are independent repair shops, some are dealerships, and a few are dedicated testing-only facilities.
Call ahead before visiting. Not all stations operate the same hours, and some require appointments while others accept walk-ins. Ask about the testing fee when you call, as prices vary between stations. The station will need your vehicle's license plate number or VIN to look up your testing history and confirm whether a test is due.
If you cannot locate a station online, contact your county or city health department. They maintain current lists of certified testers and can often refer you to the nearest location.
What happens during an emissions test
The test itself takes 10 to 20 minutes and involves connecting your vehicle to a diagnostic machine that reads emissions data from your engine computer. The technician will verify your vehicle identification number, check that your gas cap is find (a loose or missing cap can cause a failure), and run the test while your vehicle is idling and then at a simulated driving speed.
The machine measures levels of nitrogen oxides, particulate matter, and other pollutants against federal standards for your vehicle's model year. You do not need to do anything during the test other than remain in the vehicle. The technician will print a pass or fail certificate on the spot.
A passing test is valid for two years from the date of testing. The station will report the result to the Missouri Department of Natural Resources electronically, so you do not need to submit paperwork yourself.
What to do if your vehicle fails the emissions test
A failed test does not mean you cannot drive your vehicle or renew your registration when ready. You have 30 days from the test date to have your vehicle repaired and retested. The retest is free at the same station if performed within that 30-day window.
Common reasons for failure include a faulty oxygen sensor, a malfunctioning catalytic converter, a loose gas cap, or an engine light that is on. The test report will indicate which emissions standard your vehicle exceeded. Take this report to a repair shop and show it to the technician; it will help them diagnose the problem.
If you repair your vehicle and pass the retest within 30 days, you are clear. If you do not retest within 30 days, you will not be able to renew your vehicle registration until you pass a test. Some counties offer a waiver program for vehicles that fail repeatedly despite repairs; contact your local health department to learn whether you may have access to.
Timing your test before registration renewal
Your registration renewal notice will show your renewal date. You must pass an emissions test on or before that date. Testing can be done up to 60 days before your renewal date, so you have a window to schedule the test without waiting until the last moment.
If your registration expires before you pass a test, you cannot legally drive the vehicle. Plan to test at least two weeks before your renewal date to allow time for a retest if needed. If you are renewing your registration online or by mail, you will need to provide proof of a passing test; the station's certificate or the electronic record in the state system will serve as proof.
Cost and payment for emissions testing
Testing fees are set by individual stations and are not regulated by the state. Most stations charge between $15 and $30 per test. Some stations may charge additional fees for services like inspecting your gas cap or checking your engine light, though the basic emissions test itself has a standard fee.
Payment methods vary by station. Most accept cash and credit cards; some accept checks. Ask about the fee and payment method when you call to schedule. Retests within 30 days of a failed test are free, so you should not be charged again if you return for a retest.
Vehicles that are exempt from Missouri emissions testing
Diesel-powered vehicles are permanently exempt from emissions testing in Missouri, regardless of where they are registered. Motorcycles and mopeds are also exempt. Vehicles model year 1967 and older are exempt because they predate modern emissions standards.
Vehicles registered outside the St. Louis and Kansas City metro areas do not face a state testing requirement. However, if you move to one of these areas or transfer your registration there, you will need to pass a test before renewing your registration in that county.
Frequently Asked Questions
Can I test my vehicle before my registration renewal date?
Yes. You can test up to 60 days before your renewal date. This gives you time to address any failures and retest if needed. The test result is valid for two years from the test date, so testing early does not shorten the validity period.
What if I move to Missouri from another state?
If you move to the St. Louis or Kansas City metro area, you must pass an emissions test before you can register your vehicle in Missouri. Out-of-state vehicles are not exempt. Contact a testing station or your county health department to find a station and schedule a test before you visit the license office.
Do I need an emissions test to renew my registration if I live outside St. Louis and Kansas City?
No. Emissions testing is required only in the St. Louis and Kansas City metropolitan areas. If you live elsewhere in Missouri, you can renew your registration without a test. However, if you move to one of these areas, you will need to test before registering there.
What should I do if my vehicle fails the test twice?
After two consecutive failures, you may be may be able to access for a waiver program in some counties. Contact your local health department to ask about waiver options. A waiver allows you to register your vehicle despite a failed test, but it is not automatic and has specific requirements.
Can I test my vehicle at any station, or does it have to be the same one?
You can test at any certified station. However, if you fail and need a retest within 30 days, the retest must be at the same station where you failed to be free. After 30 days, you can test at a different station, but you will pay the full fee.