The Gateway Vehicle Inspection Program will emissions test even model year vehicles during even calendar years and odd model year vehicles during odd calendar years. An emissions test is also required any time an eligible vehicle undergoes a title change. At the time of the title transfer, the seller is required to provide the purchaser with a valid emissions inspection compliance certificate or compliance waiver.  The Missouri Department of Revenue will continue to mail vehicle registration papers 60 days prior to vehicle plate expiration to notify motorists when to have an emissions test and safety inspection performed.

Vehicles Subject to an Emissions Test and Safety Inspection

All 1996 and newer gas-powered vehicles and 1997 and newer diesel-powered vehicles 8,500 pounds or less gross vehicle weight rating registered in the St. Louis nonattainment area will be subject to a combined emissions test and safety inspection once every two years. Even model year vehicles are tested in even calendar years, and odd model year vehicles are tested in odd calendar years. The nonattainment area includes registered vehicles in St. Louis City, Franklin, Jefferson, St. Louis and St. Charles counties.

Used vehicles being sold are required by state law to be emissions tested and safety inspected by the seller prior to sale, regardless of the model year. There are more restrictive requirements for used vehicle dealers. For more information about the inspection requirements for used vehicles being sold, please see Buying and Selling a Used Vehicle page.

The program will also emissions test vehicles with at least 51 percent of their annual miles driven in the ozone nonattainment area, regardless of where registered.

Fuel Flexible, Dual Fuel, and Hyrid Electric Vehicles
All vehicles that are powered by gasoline or diesel fuel are subject to an emissions test. This includes fuel flexible vehicles that burn ethanol (E-10 or E-85), methanol (M-10 or M-85), or biodiesel (B-5, B-20, and B-100), dual fuel vehicles that have either propane, liquified natural gas, or compressed natural gas fuel tanks and gasoline or diesel fuel tanks, and hybrid electric vehicles that have electric motors coupled with gasoline or diesel engines.

Gray Market Vehicles
Gray market vehicles were sold in another country and imported into the U.S.

If a vehicle is gasoline-powered and 8,500 pounds or less gross vehicle weight rating and is going to be licensed by the Department of Revenue Motor Vehicle Bureau, it needs an emissions test. The weight rating is usually found on a label on the inside of the driver's door.

It is a violation of federal law to import a vehicle into the U.S. that does not meet the U.S. Environmental Protection Agency emission standards. Therefore, gray market vehicles are tested using the same emission standards as a vehicle sold in the U.S.

For more information about imported vehicles, visit this U.S. Environmental Protection Agency website,

For a list of Canadian vehicles considered by EPA to conform with U.S. emissions requirements, visit this U.S. EPA website,

Example: An imported 2001 Mercedes-Benz will receive an OBD emissions test biennally in odd years.

Switched Engine Vehicles
Engine-switched vehicles have had the manufacturer's original certified engine configuration removed and replaced with another engine configuration.

What happens if a required vehicle is not tested?
Registration will be denied, and new stickers will not be issued for the vehicle.

Does my vehicle need an emissions test if I just moved here from outside the emissions test area?
No, an emissions test is not required if you relocate the vehicle to the St. Louis ozone nonattainment area because there is no change of vehicle ownership. An emissions test will be required the next time your vehicle's registration expires as follows: even-model year vehicles will be emissions tested in even calendar years, and odd model year vehicles will be emissions tested in odd calendar years.

Does my vehicle need an emissions test for a temporary permit?
No, an emissions test is not required. In fact, as of July 1, 2001, the safety inspection is no longer required.

Vehicles Exempt from Emissions Testing

All vehicles that do not contain on-board diagnostic computer equipment will be exempt from the emissions testing requirements, however a safety inspection will still be required. Safety inspections are required biennially regardless of calendar or model years. Please call 314-416-2115 for any questions not answered here regarding emissions exemptions.

Exempted vehicles include

  • 1995 and older gas-powered vehicles;
  • 1996 and older diesel-powered vehicles;
  • New motor vehicles, not previously titled and registered, for the four-year period following their model year of manufacture, with fewer than 40,000 miles at the first required biennial safety inspection;
  • New and unused vehicles, with model years within two years of the calendar year, that have odometer readings of less than 6,000 miles at the time of original sale by the manufacturer or dealer; and
  • Motor vehicles that are driven fewer than 12,000 miles between biennial safety inspection are exempt from the emissions testing requirements until they fall outside the listed criteria.
  • See Waiver Applications and Exemption Requests to apply for mileage-based exemptions.
  • Vehicles purchased new and unused from a dealer in the calendar year preceding the vehicle's model year (eg. a 2007 model year vehicle purchased in 2006), whose license plates come due for renewal in the calendar year that is the same as the model year, are exempt from safety and emission inspection requirements in that calendar year. Please contact the Department of Revenue for verification of this exemption.
  • Plug-In Hybrid Electric Vehicles.


Other exemptions include


Does my historic vehicle need an emissions test?
No, historic vehicles are exempt from emissions testing. According to state statues, any motor vehicle more than 25 years old that is owned solely as a collector's item and is used or intended to be used for exhibition and educational purposes can be registered as an historic vehicle. When historic plates are initially registered, a vehicle emissions test is not necessary.

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