A Class B exempt test is a shorter emissions test for certain older or specialty vehicles that don't meet the standard testing requirements

If your vehicle is older, has low mileage, or falls into a specific category like a classic car or motorcycle, your state may allow you to take a Class B exempt test instead of the full Class A test. This test is shorter and less detailed than the standard emissions check, but it still verifies that your vehicle isn't releasing excessive pollutants. The test exists because some vehicles genuinely cannot be tested using standard equipment or procedures — not because they're exempt from emissions rules entirely.

Whether you're required to take this test depends on your vehicle's age, type, and your state's specific rules. Some states don't use the Class B category at all, so check your state's emissions testing website or your local testing station to know what applies to you.

Key Takeaways

  • A Class B exempt test is a shortened emissions test for vehicles that cannot undergo standard testing, such as motorcycles, vehicles over a certain age, or those with extremely low annual mileage.
  • The test still measures emissions but uses simpler procedures than the full Class A test, and your vehicle must still pass to receive a passing result.
  • Not all states offer Class B exempt testing, and the rules about which vehicles may have access to vary by state and sometimes by county.
  • You cannot choose to take a Class B exempt test if your vehicle is required to take the standard Class A test — the testing station determines which test applies based on your vehicle's details.

Which vehicles typically may have access to for Class B exempt testing

Motorcycles are the most common vehicles that take a Class B exempt test. Because motorcycles have different engine designs and exhaust systems than cars and trucks, standard testing equipment often cannot be used on them. A Class B test measures their emissions through a simpler visual inspection or a basic tailpipe reading instead.

Vehicles manufactured before a certain year — often the mid-1970s or earlier, depending on your state — may also may have access to. These older vehicles were built before modern emissions standards existed, and retrofitting them with testing equipment can be impractical or impossible. Some states also allow Class B exempt tests for vehicles with extremely low annual mileage, such as classic cars that are driven only a few hundred miles per year.

Diesel vehicles, vehicles with alternative fuel systems, and specialty vehicles like RVs or commercial trucks sometimes fall into this category as well. The exact rules depend entirely on your state's emissions program, so contact your testing station or state environmental agency to confirm whether your specific vehicle qualifies.

What happens during a Class B exempt test

A Class B exempt test is faster than a standard Class A test because it skips the detailed dynamometer testing or the computer-based diagnostic checks. Instead, the technician typically performs a visual inspection of your vehicle's emissions system — checking hoses, connections, and the condition of the catalytic converter if your vehicle has one — and then measures the tailpipe emissions directly.

For motorcycles, the technician may use a handheld emissions meter placed near the tailpipe while the engine runs at idle and at a higher RPM. The test measures the levels of carbon monoxide and hydrocarbons in your exhaust. Your vehicle passes if those levels fall below the state's threshold for Class B vehicles, which is often less strict than the Class A standard because older or specialty vehicles cannot always meet modern standards.

The entire test usually takes 15 to 30 minutes, compared to 45 minutes or more for a full Class A test. You'll receive a pass or fail result on the spot, and if you pass, you can use that result to renew your vehicle registration.

How Class B exempt differs from Class A testing

The main difference is complexity. A Class A test uses a dynamometer — a machine that simulates driving conditions while measuring emissions under load — or an on-board diagnostic (OBD) scan that reads your vehicle's computer. A Class B exempt test skips this step and measures only what comes out of the tailpipe at idle and light acceleration.

Class B tests also have different pass standards. Because older vehicles and motorcycles cannot reasonably meet modern emissions limits, the thresholds for passing are higher. A vehicle that would fail a Class A test might pass a Class B exempt test, and that's intentional — the test acknowledges that these vehicles operate under different rules.

You also cannot choose which test to take. If your vehicle qualifies for Class B exempt testing, that's what you'll receive. If it doesn't may have access to, you must take the Class A test, even if you'd prefer the shorter version. The testing station determines this based on your vehicle's year, type, and your state's rules.

State-by-state variation in Class B exempt rules

Not every state uses a Class B exempt category. Some states have only one emissions test type, while others have multiple categories with different names and requirements. California, for example, has its own system that differs from states following federal EPA guidelines.

Among states that do offer Class B exempt testing, the rules about which vehicles may have access to can differ significantly. One state might test motorcycles under Class B while another requires them to take the standard test. The year cutoff for older vehicles — the point at which a vehicle becomes old enough to may have access to — varies by state, sometimes ranging from the 1970s to the 1990s.

Some states also allow Class B exempt testing only in certain counties or regions, depending on local air quality needs. Before your test, check your state's emissions testing program website or call your local testing station to confirm the exact rules that explore to your vehicle and location.

What to bring and how to prepare for a Class B exempt test

Bring your vehicle registration, proof of insurance, and a valid photo ID. The testing station will use your registration to confirm that your vehicle qualifies for Class B exempt testing and to record the result in the state system.

Before you arrive, make sure your vehicle's engine is in reasonable condition. If your check engine light is on, have that addressed first — even though Class B tests are simpler than Class A tests, a vehicle with active engine problems is more likely to fail. If your vehicle has been sitting unused for weeks, run it for 10 to 15 minutes before the test to warm up the engine and clear out any stale fuel.

You don't need to do anything special to prepare beyond normal vehicle maintenance. Class B exempt tests don't require a full tank of gas, a specific tire pressure, or any other special conditions the way some Class A tests do. Just show up with a vehicle that runs and a valid ID.

What to do if your vehicle fails a Class B exempt test

If you fail, the testing station will give you a report showing which emissions exceeded the limit. For motorcycles, this is usually carbon monoxide or hydrocarbons. For older vehicles, it's typically the same.

You have a set number of days — usually 30 to 60, depending on your state — to fix the problem and retest. Common fixes include replacing a spark plug, cleaning the fuel injectors, or having a mechanic inspect the exhaust system for leaks. Some states allow you to retest at the same station without paying again if you return within the grace period.

If you cannot get your vehicle to pass, some states offer a waiver or extension if you can show that you've made a good-faith repair attempt. Contact your state's emissions program office to ask about your options. In rare cases, if your vehicle is too old or too damaged to repair, you may be able to register it as non-operational or seek an exemption, but this varies by state.

Frequently Asked Questions

Can I take a Class B exempt test if my vehicle qualifies for Class A?

No. The testing station determines which test your vehicle receives based on its age, type, and your state's rules. You cannot choose to take the simpler test if your vehicle is required to take the standard Class A test. If you believe your vehicle qualifies for Class B exempt testing, ask the station to review your vehicle's details before the test begins.

Do I have to pass a Class B exempt test to register my vehicle?

Yes, in states that require emissions testing. A passing Class B exempt test result is just as valid as a passing Class A result for registration purposes. If you fail, you must either fix the vehicle and retest, or seek a waiver or extension from your state's program.

How much does a Class B exempt test cost?

Testing fees vary by state and testing station, typically ranging from $15 to $50. Some states set a fixed fee, while others allow stations to charge within a range. Call your local testing station to ask about the exact cost before you arrive.

What if my motorcycle has an aftermarket exhaust system?

Aftermarket exhausts can affect emissions readings, and some may cause your vehicle to fail. The technician will measure what comes out of your tailpipe regardless of the exhaust type. If you've recently installed an aftermarket system and are concerned about passing, have a mechanic check the emissions before you test.

Can I retest the same day if I fail a Class B exempt test?

Most testing stations do not allow same-day retesting. You'll need to fix the problem and return on a different day. Some states waive the retest fee if you return within 30 days, but policies vary. Ask the station about their retest policy when you receive your fail result.