Vehicle Inspection and Emissions Testing: How State Checks Work
Emissions testing is a state-run check of a vehicle's exhaust and onboard computer, and 29 states require an emissions test to register or renew a vehicle, according to Kelley Blue Book. Most programs cover only certain counties, and official fees in our snapshot run from $0 to $35.
Your state DMV or environment agency runs each inspection through licensed stations and links the result to your registration. Covr does not perform inspections; the Covr app stores your test results and reminds you when the next one is due.
Last reviewed: October 9, 2026 · Covr editorial team
At a glance
- What it is: an emissions test reads your vehicle's onboard computer (1996 and newer models) or samples tailpipe exhaust (older models) for pollutants such as carbon monoxide, nitrogen oxides and hydrocarbons.
- Who needs it: registration in 29 states depends on a passing emissions test, per Kelley Blue Book, but usually only in metro counties with ozone problems.
- How often: every two years in Illinois, Wisconsin, Connecticut and Maryland; every year in Texas emissions counties, per the state programs.
- What it costs: from free at Illinois state stations to $35 in Colorado, per the official programs in our snapshot.
- Automatic fail: a lit "Check Engine" light, according to the Arizona Department of Transportation.
- If you fail: you repair the vehicle and retest before the registration can be renewed.
What Emissions Testing Is
Emissions testing is an official inspection that confirms your vehicle's pollution controls work before the state renews its registration.
Emissions Test Meaning
An emissions test, also called an emission inspection, measures what your vehicle releases or checks the computer that controls those pollutants. The Illinois EPA explains that motor vehicle exhaust contains carbon monoxide, nitrogen oxides and hydrocarbons, which lead to ground-level ozone (smog). Under the federal Clean Air Act (42 U.S.C. § 7511a), large urbanized areas that do not meet the national ozone standard must run vehicle inspection programs, which is why testing is tied to vehicle registration in those areas.
Emissions Inspection vs. Safety Inspection
An emissions inspection and a safety inspection are separate checks. The emissions check looks at exhaust and emission-control equipment, while a vehicle safety inspection looks at parts such as brakes, tires, lights and steering. Some states require one, some require both, and some require neither. Your state DMV website is the only reliable answer.
Smog Check, E-Check and Other Names
Emissions inspection programs go by several names. California drivers say smog check, Progressive describes the test as an "e-check", Maryland runs the Vehicle Emissions Inspection Program (VEIP), and Illinois runs the Illinois Air Team stations. The test itself works the same way whatever the program calls it. California's smog check rules show how exemptions work: the California DMV, checked by Covr on October 10, 2026, exempts gasoline vehicles less than 8 years old by model year, 1975 and older gasoline models and electric vehicles from the renewal smog check.
What an Emissions Test Checks
An emissions inspection checks 3 things: the onboard diagnostic computer or the tailpipe exhaust, the gas cap and the emission-control parts.
| Inspection type | Vehicles | What the inspection reads | Source |
|---|---|---|---|
| OBD-II scan | Most 1996 and newer vehicles | Trouble codes and readiness monitors in the onboard computer | Illinois EPA, Texas DPS |
| Tailpipe or dynamometer test | Older vehicles without OBD-II | Exhaust gases sampled by a probe | myAZcar.com test types |
| Safe-to-test and visual check | Vehicles in the AirCare Colorado program | Fluid leaks, tires and visible emission equipment | AirCare Colorado |
OBD-II Scan for 1996 and Newer Vehicles
The On-Board Diagnostic (OBD-II) emissions inspection applies to most 1996 and newer vehicles, according to the Illinois EPA and the Texas Department of Public Safety, so by Covr's arithmetic the oldest vehicles read by scanner are 30 years old in 2026. A technician plugs a scanner into the diagnostic port under the dashboard and reads stored trouble codes and readiness monitors. The Illinois EPA notes that the OBD inspection finds malfunctioning emission control systems, and repairing them also improves performance and fuel economy.
Tailpipe and Dynamometer Tests for Older Vehicles
Older vehicles without OBD-II get a tailpipe emissions inspection: a probe samples exhaust while the engine idles or while the vehicle runs on a dynamometer, a treadmill-like roller. Arizona's emissions program lists steady-state loaded/idle and opacity inspections next to the OBD inspection, with separate fees for each type on myAZcar.com.
Gas Cap and Visual Equipment Checks
Inspection staff also look at the gas cap and the emissions parts you can see. A missing or loose gas cap can fail the evaporative check. AirCare Colorado also issues an "Unable to Test" form when a vehicle has visible fluid leaks or worn tires.
Which States Require Emissions Testing
Emissions testing is required for registration in 29 states, according to Kelley Blue Book, but in most of them the requirement covers only specific counties or metro areas.
Why Only Some Counties Test
Air quality decides where emissions inspection is required. The Illinois EPA tests vehicles in the Chicago and Metro-East St. Louis areas because ozone there still exceeds the federal standard. Arizona tests in the Phoenix and Tucson metro areas, including vehicles that commute into them, and the Wisconsin DMV requires tests for vehicles kept in 7 southeastern counties: Kenosha, Milwaukee, Ozaukee, Racine, Sheboygan, Washington and Waukesha. Maryland tests in 15 counties, according to the Maryland MVA.
Emissions Programs in 8 States
Covr compiled this emissions inspection table on October 9, 2026 from the official program pages and state answers in the Google results for the query; fees and schedules can change, so confirm on the agency site before you go.
| State | Where testing is required | How often | Official fee | Source |
|---|---|---|---|---|
| Arizona | Phoenix and Tucson metro areas | Before registration renewal | $16.15 OBD test; $12.25–$23.75 other tests | ADOT, myAZcar.com |
| Colorado | Program counties | Every 2 years (1982 and newer); yearly (1981 and older) | $35; $20 for 1981 and older | Colorado DMV, AirCare Colorado |
| Connecticut | Program area on ctemissions.com | Every 2 years | See ctemissions.com | CT Emissions Program |
| Illinois | Chicago and Metro-East St. Louis areas | Every 2 years | Free at state stations | Illinois EPA, Illinois Air Team |
| Maryland | 15 counties | Every 2 years | $30 at a station; $26 at a kiosk | Maryland MVA |
| Texas | Emissions counties (Dallas-Fort Worth, Houston, Austin, El Paso areas) | Every year | $11.50–$18.50, by county | Texas DPS |
| Virginia | Northern Virginia (RAPIDPASS on-road option) | Per state schedule | $28–$30 | RAPIDPASS Virginia |
| Wisconsin | 7 southeastern counties | Every other year | See wisconsinvip.org | Wisconsin DMV |
According to Covr's comparison of these 8 official programs on October 9, 2026, an emissions test cost between $0 and $35, and 5 of the 8 programs test every 2 years.
Who Is Exempt
Emissions inspection exemptions differ by state and are printed on the registration renewal notice. The Arizona Department of Transportation exempts vehicles 5 years old or less, 1966 and older models, and electric vehicles. In Colorado, the DMV program exempts new vehicles from emissions inspection for their first 7 model years, according to AirCare Colorado. Illinois inspects most 1996 and newer gasoline vehicles once they are 4 years old, so electric vehicles, most diesels and motorcycles are not tested there.
State Safety Inspections and States Phasing Them Out
State safety inspections are a separate requirement from emissions tests. Each state DMV decides whether to require a periodic safety check.
What a Vehicle Safety Inspection Covers
A vehicle safety inspection checks the parts that keep the vehicle controllable and visible: brakes, tires, lights, horn, wipers, steering and suspension. The state sets the checklist and licenses the stations that perform the inspection, and a passing vehicle usually gets a sticker or an electronic record tied to its registration.
Brake Inspection: What the Check Covers
A brake inspection is a road test plus a wheel-off look at the brake parts: the technician feels the pedal and listens for grinding, then measures pad thickness, checks rotors or drums for grooves and cracks, and looks at calipers, brake lines and fluid. Brake pads thinner than 3 millimeters (about 1/8 inch) are due for replacement, according to Mitti by SafetyCulture. Between state checks, AutoZone recommends a brake inspection at least once a year or every 12,000 miles, whichever comes first, as cited in Covr's brake pad guide. Brake repair prices after an inspection are covered in Covr's separate repair-cost guides.
Tire Inspection
A tire inspection during a safety check covers tread depth, sidewall damage and inflation, because worn or damaged tires can fail a state inspection or stop an emissions test: AirCare Colorado will not test a vehicle with worn tires.
Texas: Safety Inspections Ended, Emissions Tests Remain
Texas is the clearest example among the states phasing out mandatory vehicle inspections. The state eliminated the annual safety inspection for non-commercial vehicles. Every non-commercial vehicle still pays a $7.50 inspection program replacement fee, according to the Texas Department of Public Safety. Vehicles registered in Texas emissions counties still need a yearly emissions test, and commercial vehicles still need an annual inspection with a $40 maximum fee.
How to Check Your State's Inspection Rules
State inspection rules change more often than most drivers expect. Check the official source rather than a list. Your renewal notice tells you whether a test is due; Arizona, for example, tells drivers to read the notice carefully because they may not need a test that year. The state agency website lists the current counties, exemptions and fees.
How Much Emissions Testing Costs
Emissions testing costs from $0 to $35 at the official programs in our October 2026 snapshot, and the state usually caps or sets the fee.
Official Fees by State
The official emissions inspection fee depends on the state and the test type. Illinois tests for free at state stations, Arizona charges $16.15 for an OBD test, Texas stations charge up to $11.50 or $18.50 depending on the county, Virginia's RAPIDPASS fee is $28 to $30, Maryland charges $30 at a VEIP station or $26 at a self-service kiosk, and Colorado charges $35. Spread over the testing cycle, Covr's arithmetic from the same official fees puts the yearly cost at $17.50 in Colorado ($35 every 2 years) and $15 in Maryland ($30 at a station every 2 years), compared with $11.50 to $18.50 every year in Texas emissions counties.
Retest Fees and Registration Add-Ons
The full cost of vehicle inspection can include more than the test fee. AirCare Colorado gives one free retest within 30 days at the same station, and Texas adds the $7.50 replacement fee when you renew with the Texas DMV. Repairs after a failed test are a separate cost set by the repair shop.
Pre-Purchase Inspection: A Different Service
A pre-purchase inspection is a voluntary mechanic check of a used vehicle before you buy it, not a state requirement. The shop sets the price. The mechanic's report does not replace a test the state requires at a change of ownership. Wisconsin, for example, requires a test within 45 days when an owner is added or removed.
How to Prepare for an Emissions Test
Emissions testing preparation takes 5 steps, and the most important one is fixing any warning light before you go.
What to Bring to an Emissions Test
To get a vehicle emissions inspection you need 3 things: the vehicle, a renewal notice or registration document, and the fee. Wisconsin asks for 1 of the following: the renewal notice sent by mail or email, the certificate of registration, the letter you received, a prior test report, or the Wisconsin title. Maryland asks for the registration card or the test notice plus the fee.
How to Pass an Emissions Test
Passing an emissions inspection is easier when you follow 5 steps in order.
- Fix the cause of a lit "Check Engine" light; ADOT says a vehicle cannot pass while the light is on.
- Arrive with at least 1/2 tank of fresh fuel, per ADOT.
- Drive at highway speed for at least 15 minutes first, as Larimer County, Colorado advises.
- Tighten or replace the gas cap.
- Do not disconnect the battery or clear codes right before the test; OBD-II readiness monitors need normal driving to reset.
Where to Get an Emissions Test
Emissions testing centers are either state-run stations or licensed private shops. Connecticut tests through more than 200 privately owned service facilities, according to the CT Emissions Program, while Wisconsin runs 2 centralized facilities with self-service kiosks that are open 24/7 for 2007 and newer vehicles. Arizona also advises finishing the test before you visit a state office, and an Arizona vehicle that is not yet registered can be driven to the test on a $1 Restricted Use 3-Day Permit, per ADOT as reviewed on October 9, 2026.
Does Valvoline or Walmart Do Inspections?
Valvoline can do vehicle inspections only at locations licensed as state test stations, and the same rule applies to Walmart Auto Care and other chain shops. Whether a Valvoline or Walmart store offers the test depends on your state program and on the individual store, so search the station locator on your state's official program website before you drive to a chain location.
What Happens If You Fail
A failed emissions test means you cannot renew the registration until the vehicle passes or qualifies for a waiver or exemption.
Repair and Retest
Emissions repair and retest is the standard route after a failure. A shop diagnoses the trouble codes or exhaust readings, repairs the fault, and you retest after the readiness monitors reset. AirCare Colorado gives one free retest within 30 days at the same station, and Wisconsin asks owners to contact its program contractor, OPUS, when a vehicle has failed two consecutive tests.
Waivers, Exemptions and Out-of-State Vehicles
Emissions waiver and exemption rules differ by state. Arizona lists waivers and an out-of-state exemption for vehicles away for an extended period. Wisconsin accepts out-of-state OBD-II test results and grants a temporary exemption when the vehicle is kept where no OBD-II testing is offered, with the test due when the vehicle returns.
How a Failed Test Affects Registration
Registration is where the emissions rule is enforced. The Illinois EPA works with the Illinois Secretary of State to deny plate renewals to vehicles that do not comply, and Arizona sends results to the state electronically. Arizona also tells drivers to test no sooner than 90 days before the due date, a window of about 3 months by Covr's arithmetic, which leaves time to repair and retest.
How Covr Helps You Keep Track
Inspection paperwork is one of 4 kinds of vehicle records the Covr app keeps in one place.
What You Can Do in the Covr App
The Covr app does not test or inspect vehicles; it helps you keep track of the official ones:
- Store your test report, certificate, registration card and insurance card on your phone.
- Set a reminder for the next test due date; in 2-year programs such as Illinois and Maryland, the next test comes due about 24 months after the last one, so a reminder at 21 months leaves a 3-month buffer for repairs, by Covr's arithmetic.
- Keep a maintenance history with mileage, including repairs after a failed test, and check it against service intervals by mileage.
- Track repair and fuel costs for each vehicle.
The Covr app for car owners is free to download on Google Play. Book the test itself with your state's official program.
Sources and Methodology
Our methodology: every rule, fee and schedule on this page was last reviewed by Covr on October 9, 2026 against the official source named next to it: ADOT and myAZcar.com (Arizona Department of Environmental Quality), the Illinois EPA and Illinois Air Team, Wisconsin's state program page, CT Emissions, the Colorado state program and AirCare Colorado, the Maryland MVA, the Texas Department of Public Safety, RAPIDPASS Virginia and Larimer County, the California DMV smog inspection page (checked October 10, 2026) and AutoZone's brake inspection interval as cited in Covr's brake pad guide, plus the Kelley Blue Book state count and the Google results for the query on that date. We did not publish a list of states with periodic safety checks because we could not verify one against each state agency. Written and fact-checked by the Covr Editorial Team under our editorial policy. This page is general information, not legal advice; rules, fees and schedules depend on your state, county and vehicle. Read our editorial policy or contact us with a correction.
Emissions Testing FAQ
What is an emissions test?
An emissions test is a state-required check of a vehicle's onboard computer or tailpipe exhaust that confirms the pollution controls work. Passing it is a condition of registration in the counties and states that run a program.
How do I know if I need an emissions test?
Your registration renewal notice tells you whether an emissions test is due, and your state agency website lists the counties, model years and exemptions that apply. In Arizona, for example, the test can be done up to 90 days before the registration expires.
Do electric vehicles need an emissions test?
Electric vehicles are exempt from emissions inspection in the programs in our snapshot: the Arizona Department of Transportation lists electric vehicles as exempt, and the Illinois program inspects gasoline vehicles. Registration of an electric vehicle can still require other state checks, so read your renewal notice.
Can I pass an emissions test with the check engine light on?
A vehicle with a lit check engine light fails the emissions test. The Arizona Department of Transportation states that vehicles cannot pass emissions testing while the "Check Engine" light is on, so diagnose and repair the fault before the test.