Colorado Emissions Test
Through Air Care Colorado, gas, hybrid, and diesel cars are tested in 9 Colorado counties. Model years up to 2019 are covered for 2026. For 1982 and newer models, testing comes every 2 years; 1981 and older models need it yearly.
What vehicles have to be tested?
For 2026, a green band marks the model years Colorado tests. Exemption covers the newest 7 model years, with 4 for diesels instead. Cars from 1975 or earlier can be excused when they carry collector plates.
Use the model year and fuel to check if your car needs a test.
Colorado emissions test at a glance
| Program | Air Care Colorado |
|---|---|
| Where | Included: Boulder County, Larimer (part) County, Broomfield County, Arapahoe (part) County, Denver County, Weld (part) County, Douglas County, Adams (part) County, Jefferson County, 9 total |
| Fuels tested | Gas, hybrid, diesel |
| Model years tested in 2026 | up to 2019 |
| How often | 1982 and newer models: every 2 years; 1981 and older models: every year |
| The test | Which method is used depends on the car: OBD plug-in, dynamometer (rolling road), or idle. A gas cap test also happens. |
| Fee | $35 ($20 for 1981 and older cars) |
| New cars | Exempt for the newest 7 model years; diesels get 4 |
| Older cars | Cars from 1975 or earlier can be excused when they carry collector plates |
| Waiver | After at least $715 in documented emissions repairs and a failed retest, a repair waiver is possible; smoking, tampered, or gas cap failures don't qualify |
How the test works, and what if the car fails?
For an OBD plug-in test, a reader goes into the port below the dashboard; the inspector then reads the saved computer data. Both are required: the check engine light stays off, and the self-checks (readiness monitors) are complete.
Older cars usually get the tailpipe test: exhaust output is measured with a probe.
Because a loose cap lets fuel vapor escape, the gas cap check confirms the cap seals.
When a car does not pass, the report lists the failed items. That fault comes first: Fix it, then go back to test again.
After repairs, if the car still fails, Colorado allows a repair waiver. It requires at least $715 in documented emissions repairs and a failed retest; smoking, tampered, or gas cap failures are excluded.