States that currently require emissions testing

Thirty-four states and the District of Columbia require some form of emissions testing as part of vehicle registration or inspection. However, the rules vary significantly by state—some test all vehicles, others only those in certain counties, and some exempt older cars entirely. The federal government sets the baseline standards through the Environmental Protection Agency (EPA), but each state decides whether to adopt those standards and how strictly to enforce them.

The states with the most comprehensive programs are California, New York, Massachusetts, Connecticut, Delaware, Maine, Maryland, New Jersey, New Mexico, New Hampshire, New York, Oregon, Pennsylvania, Rhode Island, Texas, Vermont, Virginia, and Washington. These states test either all registered vehicles or all vehicles in designated urban areas. The remaining states that test emissions do so only in specific counties or metropolitan regions where air quality has historically been poor.

If you live in a state without emissions testing, you still need to pass a safety inspection in most cases—that is a separate requirement. Emissions testing specifically measures what comes out of your tailpipe: nitrogen oxides, particulate matter, carbon monoxide, and hydrocarbons. A safety inspection checks your brakes, lights, wipers, and steering.

Key Takeaways

  • Thirty-four states plus Washington, D.C. require emissions testing, but the rules differ by state—some test all vehicles, others only in certain counties or for specific model years.
  • Your vehicle's model year, engine type, and the county where you register it determine whether you must test, not your state alone.
  • Emissions tests measure tailpipe output (carbon monoxide, nitrogen oxides, and particulates) and typically cost between $25 and $75 depending on your state.
  • Vehicles that fail emissions testing can often be retested after repairs, and some states offer waivers or exemptions for vehicles that repeatedly fail due to repair costs.
  • If you move to a state with stricter emissions rules, your vehicle may need repairs to pass—plan for this before relocating with an older car.

How emissions testing works in your state

The test itself is straightforward: you drive to a certified testing station, the technician plugs a diagnostic scanner into your vehicle's onboard computer, and the machine reads the emissions data. For older vehicles without that computer connection, the technician may perform a tailpipe test where a probe measures the gases directly. The entire process usually takes 10 to 15 minutes.

Your vehicle passes or fails based on whether its emissions fall within the limits your state has set. Those limits are stricter in states that have adopted California's standards (often called "CARB states" after the California Air Resources Board) than in states following the federal EPA baseline. If you fail, you receive a report showing which pollutants exceeded the limit and by how much.

Most states allow you to retest after repairs at no additional charge within a set window—usually 30 to 60 days. Some states also offer a repair cost waiver: if a repair shop estimates that fixing the emissions problem will cost more than a certain amount (often $300 to $500), you may be exempt from testing for that year or allowed to pass with a waiver.

States with no emissions testing requirement

Sixteen states do not require emissions testing at all: Alaska, Arkansas, Georgia, Idaho, Indiana, Iowa, Kansas, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee, Utah, West Virginia, Wisconsin, and Wyoming. In these states, you still need a safety inspection in most cases, but there is no measurement of what your engine produces.

If you own an older, high-mileage vehicle and live in one of these states, you have no emissions hurdle to clear at registration. However, if you move to a state that does test, your vehicle may fail when ready if it has not been maintained to that standard. Conversely, if you move from a testing state to a non-testing state, you will no longer need to pass an emissions test.

Exemptions and special cases

Most states exempt vehicles below a certain age—commonly 1975 or earlier, though some use 1996 as the cutoff because that is when modern onboard diagnostics became standard. Diesel vehicles are often tested under different standards than gasoline vehicles, and some states exempt light trucks or vehicles over a certain weight. New vehicles typically have a grace period of three to five years before their first test.

If your vehicle fails emissions testing and the repair cost exceeds your state's threshold (usually $300 to $500), you may receive a waiver that allows you to register without passing. You will still need to attempt the repair and document the cost estimate, but the waiver protects you from being unable to register. The waiver is typically good for one or two years, after which you must test again.

Some states also allow conditional registration for vehicles that fail: you can register the car with the understanding that you have a set number of days to complete repairs and retest. This prevents you from being stranded without a registered vehicle while waiting for a repair appointment.

What happens if you fail emissions testing

A failed test does not automatically prevent you from registering your vehicle, but it does require action. You will receive a detailed report showing which emissions standards your vehicle exceeded. Common failures include high carbon monoxide (often a sign of a rich fuel mixture or ignition problems), high nitrogen oxides (typically an engine timing or cooling system issue), or high particulates (often related to oil burning or a clogged filter).

Your next step is to take the report to a repair shop and have them diagnose the underlying problem. Many shops can read the same diagnostic codes your test revealed and recommend repairs. After repairs, you retest—most states allow one free retest within 30 to 60 days of the original failure. If you pass the retest, you can complete your registration.

If repairs are expensive and you cannot afford them when ready, check whether your state offers a repair cost waiver. You will need a written estimate from a repair shop showing the cost exceeds your state's threshold. With that estimate, you can register your vehicle for the year without passing, though you may be required to attempt the repair again the following year.

Emissions testing by region and county

Even within states that require testing, the rules often explore only to certain counties or metropolitan areas. Texas, for example, requires testing in Houston, Dallas, Austin, and San Antonio but not in rural areas. Pennsylvania tests in the Philadelphia and Pittsburgh regions. New York tests in the New York City area and some counties in the Hudson Valley.

If you live in a county without a testing requirement but register your vehicle in a county that does, you will need to test. If you move from a testing county to a non-testing county within the same state, you may no longer need to test. Check your state's Department of Motor Vehicles website or your county's emissions program to confirm whether testing applies to your specific location.

Some states also distinguish between OBD testing (where the scanner reads your vehicle's onboard computer) and tailpipe testing (where a probe measures gases directly). Newer vehicles in testing areas typically use OBD; older vehicles may use tailpipe testing. The location of your test station and your vehicle's age determine which method applies.

Cost and timing of emissions testing

Emissions testing costs between $25 and $75 depending on your state and whether your vehicle requires OBD or tailpipe testing. Some states bundle emissions testing with safety inspection into a single fee; others charge separately. The test itself takes 10 to 15 minutes, but you may wait longer depending on how busy the testing station is.

Testing is typically required annually or every two years, depending on your state. You can usually test any time during your registration renewal window—often the month before or after your birthday or registration expiration date. Some states allow testing up to 60 days before your registration expires; others require it within 30 days of expiration.

Plan to test early in your renewal window so you have time to address any failures before your registration expires. If you fail and need repairs, you want at least 30 days to schedule a shop appointment and retest. Waiting until the last week of your renewal period leaves you at risk of driving unregistered if repairs take longer than expected.

Frequently Asked Questions

Do I have to test my vehicle if I just moved to a state that requires emissions testing?

Yes, once you register your vehicle in that state, you must pass emissions testing as part of the registration process. If your vehicle fails, you cannot complete registration until you repair it and pass a retest. Plan for this before moving with an older car—have it inspected by a mechanic familiar with that state's standards.

What if my vehicle is too old to have an onboard computer?

Vehicles older than the cutoff year in your state (often 1975 or 1996) are typically exempt from testing entirely. If your vehicle is close to the cutoff, check your state's specific rules. Some states exempt vehicles by model year; others use the vehicle's age at the time of testing.

Can I test my vehicle in a different county than where I live?

Most states require you to test in the county where you register the vehicle, not where you live. If you register in a testing county, you must test there. If you register in a non-testing county, you do not need to test even if you work or spend time in a testing county.

What should I do if a repair shop says the emissions repair will cost more than $500?

Get a written estimate on the shop's letterhead showing the repair cost and what it addresses. Take that estimate to your state's emissions program office or DMV and request a repair cost waiver. With the waiver, you can register your vehicle without passing the test, though you may need to retest the following year.

How do I find a testing station near me?

Your state's Department of Motor Vehicles website lists all certified emissions testing stations by county. You can also call your local DMV office or search online for "emissions testing stations" plus your county name. Some states allow you to test at any certified station in your testing region, not just one specific location.