Utah Emissions Laws: Testing, Exemptions, and Waivers

Utah emissions testing requirements apply only in five counties: Salt Lake, Davis, Utah, Weber, and Cache. If your vehicle is registered anywhere else in the state, you have no testing obligation at all. If it is registered in one of the five, whether and how often you test depends on the vehicle’s model year, its fuel type, its weight, and which of those counties you’re in.

Which Counties Require Testing

Salt Lake, Davis, Utah, Weber, and Cache are the only Utah counties that mandate emissions inspections. These counties have struggled to meet national air quality standards for pollutants like ozone and fine particulate matter. The Utah Division of Air Quality sets the broader framework, and each county health department runs the day-to-day testing and waiver programs.¹

Each of the five counties also charges a small local emissions compliance fee at registration: $3 in Salt Lake, Davis, and Cache; $2 in Utah and Weber. Electric vehicles don’t pay it.²

How Often You Have to Test

Testing frequency depends on model year and county, and the counties don’t all follow the same rules.

Salt Lake, Davis, Utah, and Weber Counties

Brand-new vehicles skip testing for their first two model years. After that, vehicles under six years old test every other year on an alternating schedule: even-numbered model years test in even-numbered calendar years, and odd-numbered model years test in odd-numbered years. Once a vehicle reaches six model years old, it needs testing every year at registration renewal.³

In Salt Lake, Davis, and Utah counties, testing reaches back to model year 1968. Vehicles from 1967 and older are exempt. Weber County has a narrower window: only 1996 through 2020 (plus newer vehicles on the biennial schedule) need testing, and 1995 and older models are exempt.³

Cache County

Cache is the most lenient. Vehicles under six years old are completely exempt. Vehicles six years and older with model years 1996 through 2020 test biennially rather than annually. Models from 1995 and older are exempt.³

What the Test Actually Checks

Utah uses On-Board Diagnostics (OBD) testing for vehicles from 1996 and newer. The inspection station plugs into your vehicle’s diagnostic port and checks whether the onboard computer has flagged any emissions-related problems. Older vehicles that predate OBD systems may need a tailpipe test instead. Testing has to be done at a state-certified inspection station, and results go electronically to the Utah DMV.

One common headache: if your battery was recently disconnected or replaced, or a mechanic recently cleared diagnostic trouble codes, the OBD readiness monitors may not have finished their self-checks. The station will reject the vehicle as “not ready” even if nothing is wrong. Drive it through a normal mix of highway and city miles for a few days, then try again.

Diesel Vehicles

Diesels have their own regime. In Utah County, diesel vehicles with model years 1998 through 2021 must pass an emissions opacity test.³ The other affected counties have similar diesel requirements.

Diesel vehicles with a gross vehicle weight rating (GVWR) above 14,001 pounds are exempt from opacity testing in Salt Lake, Davis, Utah, and Cache counties.³ Utah’s diesel emissions statute also exempts farm implements and farm trucks with a GVWR of 12,001 pounds or more. Pickup trucks rated at 12,000 pounds or less can qualify for a farm-use exemption if the registered owner provides a signed statement that the truck is used exclusively for transporting farm products and supplies.⁴

Weight Cutoffs for Gasoline Trucks and SUVs

Weight-based exemptions for gasoline vehicles vary by county. In Cache County, gasoline vehicles from 2008 and newer with a GVWR above 14,000 pounds are exempt, while gasoline vehicles from 2007 and older are exempt above 8,500 pounds. Weber County exempts gasoline and CNG vehicles from 1996 through 2007 with a GVWR between 10,000 and 14,000 pounds, and any vehicle above 14,001 pounds regardless of fuel type.³ Because thresholds differ, check your county’s exemption list before assuming your truck qualifies.

Who Is Exempt

Vehicles powered exclusively by electricity are exempt from emissions inspections statewide.⁵
Motor vehicles with a model year of 1982 or older that are driven fewer than 1,500 miles per calendar year qualify for a classic-vehicle emissions exemption.⁶
Brand-new vehicles in their first one or two model years, depending on county.
Very old vehicles: 1967 and older in Salt Lake, Davis, and Utah; 1995 and older in Weber and Cache.³
Heavy vehicles above the GVWR thresholds described above.

Hybrids follow the same rules as gasoline cars. Owning a hybrid does not get you out of the inspection.

If You Fail: Repair Cost Waivers

If your vehicle fails and you’ve spent a minimum amount trying to fix it, you can apply for a repair cost waiver. The thresholds are set by county.

Salt Lake County requires at least $450 in emissions-related repairs performed by a licensed repair facility, followed by a second inspection showing that at least one of the original trouble codes was resolved. The vehicle must have had two or more trouble codes on the initial failure.⁷

Davis County uses a tiered system by model year: $450 for 1996 and newer, $350 for 1984 through 1995, $250 for 1968 through 1983, and $1,500 for heavy-duty diesel vehicles.⁸ Other counties set their own amounts; check with your county health department.

A repair cost waiver generally lets you register for one additional year. It is not a permanent pass. You’ll try again at your next renewal, and if the vehicle still can’t pass, the waiver process starts over.

Deferrals for Out-of-State Residents and Military

Utah residents temporarily out of state may qualify for a deferral from their county. The DMV requires either a passing inspection or a county-approved deferral to be transmitted electronically before it will renew your registration. Each county handles deferral applications on its own website.³

Active-duty military members stationed outside Utah can request a deferral by uploading a copy of their military orders showing they are required to be at their current location.⁹ Start the request early. If the deferral isn’t processed before your registration expires, you can end up with a lapsed registration despite having a valid reason.

What Happens If You Skip Testing

The main enforcement mechanism is straightforward: the DMV won’t renew your registration without a passing test or an approved waiver on file. Because results come in electronically, a forged paper certificate won’t work, and officers can see immediately whether a vehicle’s registration is current.

Driving without current registration because you skipped or failed emissions testing is an infraction under Utah law. The fine varies by court, and on top of it you’ll owe a penalty equal to the unpaid registration fees. A separate and much steeper penalty applies if you moved to Utah and never registered your vehicle at all: that’s a class C misdemeanor carrying a minimum $1,000 fine, though a court can reduce it to $200 if you register the vehicle before your hearing and the violation lasted less than a year.¹⁰

Tampering Is Treated Much More Seriously

Tampering with emissions controls carries far heavier consequences than failing a test. Under county health regulations enforcing the Utah Clean Air Act, tampering includes removing or altering catalytic converters, modifying exhaust or air intake systems, engine swaps on 1996-and-newer vehicles, and using emissions defeat devices. A first violation is a class B misdemeanor. A subsequent violation within two years can be charged as a class A misdemeanor.¹¹ Engine swaps on 1996-and-newer vehicles are also considered tampering under the federal Clean Air Act. Violating the diesel opacity program falls under the same class B misdemeanor framework, with escalating penalties for repeat offenses.

A Change Coming for Classic Vehicles

Utah’s 2026 legislative session passed HB 22, which replaces the old “vintage vehicle” designation with a new “classic vehicle” category effective October 1, 2026. The definition stays functionally similar: a motor vehicle or motorcycle with a model year of 1982 or older that is driven fewer than 1,500 miles per calendar year. The bill also extends the classic designation to travel trailers from 1982 or older used primarily as collector’s items for club activities, exhibitions, tours, and occasional recreational use.¹² Classic vehicles continue to qualify for the emissions exemption and also receive exemptions from certain minimum safety equipment and minimum speed requirements when driven to or from car shows and similar events.⁶

1
Utah Department of Environmental Quality. Division of Air Quality
2
Utah Legislature. Utah Code 41-1a-1223 – Local Emissions Compliance Fee
3
Utah State Tax Commission. Vehicle Inspections
4
Utah Legislature. Utah Code 41-6a-1644 – Diesel Emissions Program
5
Alternative Fuels Data Center. Electricity Laws and Incentives in Utah
6
Utah Legislature. Vintage Vehicle Amendments 2026 General Session
7
Salt Lake County. Vehicle Emissions Program – Air Quality
8
Davis County Utah. Vehicle Emissions Information
9
UCG Air Quality. Vehicle Emission Deferral Request
10
Utah Legislature. Utah Code Title 41 Chapter 1a Part 13 – Offenses and Penalties
11
Utah Department of Environmental Quality. Vehicle Emissions Control Program – Salt Lake County
12
Utah Legislature. HB 22 Vintage Vehicle Amendments