Cars and driving - Front Range
In Adams County, your car may need an emissions test
Adams County is part of the Front Range area where many gas vehicles must pass an emissions test to register, tied to the region's ozone air-quality problem.
Published June 10, 2026 - Last verified June 10, 2026
If you move to Adams County from outside the Front Range, one small surprise can come at registration time: many gasoline vehicles here have to pass an emissions test before you can renew the plates.
This is because Adams County sits inside the Denver-area emissions program. The rules turn on the vehicle’s age and type, and on where you live, so not every car is tested on the same schedule, and some newer vehicles get a break for the first several years. Rather than guess, it is worth checking the current requirement for your specific vehicle before your renewal is due.
There is a bigger reason behind it. The Denver metro and northern Front Range, Adams County included, does not currently meet the federal health standard for ground-level ozone, the main ingredient in summer smog. Vehicle emissions are one of the sources, so testing is part of the region’s effort to clean the air.
For most drivers this is just a routine errand, not a hurdle. The key is to know it exists so it does not catch you off guard at the counter.
For whether your vehicle needs a test and where to get one, check the Colorado Division of Motor Vehicles.