Are you unsure of what the laws regarding catalytic converters are in your state? We'll give you an overview of everything you need to know right here, from Federal regulations, right down to state-specific laws.
Environmental Protection Agency (EPA)
The EPA is the federal agency that sets nationwide vehicle-emissions rules under the Clean Air Act. Most 1975-and-newer passenger vehicles were equipped with catalytic converters to meet federal standards, and replacements in all States must follow EPA policy.
What it is: The Environmental Protection Agency (EPA) is a national (federal) government agency in the United States.
What it does: It sets and enforces rules that limit pollution in our air, water, and land so people stay healthy and nature is protected.
Why it exists: The EPA’s job is to reduce smog, dirty water, toxic chemicals, and other pollution that harm people and wildlife.
What it means for motorists:
- It’s illegal to remove or tamper with emissions equipment (like catalytic converters).
- Replacement parts must be legal for your state - usually EPA-compliant parts in most states, or CARB-approved parts in states that follow California’s stricter rules. (more on that below)
- EPA’s enforcement policy explains when and how aftermarket converters may be installed, and reiterates that selling, installing, or using defeat devices or removing converters is prohibited.
California Air Resources Board (CARB)
CARB is an acronym for California’s state air-quality agency called the California Air Resources Board.
What it is: A state government group that sets and enforces air-pollution rules for the state of California.
What it does: Limits how much pollution cars, trucks, and other sources can produce. It also sets testing and labeling rules for parts that affect emissions (like catalytic converters).
Why it exists: California deals with some of the worst smog in the U.S. CARB’s job is to protect public health by cleaning up the air.
What it means for motorists:
- Replacement parts that concern emissions, like catalytic converters, must be CARB-approved.
- Approved parts carry a CARB Executive Order (EO) number, which proves the part was tested and is legal for specific vehicles.
Which States Follow CARB Rules?
Federal law lets other states choose to implement California’s stricter rules instead of abiding by federal EPA rules alone. Many 'CARB states' follow California’s stricter standards, so the same CARB-approved parts are required there, too. Here’s the current list of U.S. states that follow CARB vehicle-emissions rules:
- Colorado
- Connecticut
- Delaware
- Maine
- Maryland
- Massachusetts
- Minnesota
- Nevada
- New Jersey
- New Mexico
- New York
- Oregon
- Pennsylvania
- Rhode Island
- Vermont
- Virginia
- Washington
Some states adopt all or part of the Low-Emission Vehicle (LEV) and Zero-Emission Vehicle (ZEV) rules. As technology changes, the rules for emissions products also evolve. Always check with your local lawmaking body for the latest up-to-date information information regarding emissions regulations.
For a comprehensive look into CARB-compliant catalytic converters, check out our article here.
How Do EPA vs. CARB Rules Affect Catalytic Converters?
State specific requirements depend on the state’s framework. There are a few states that have their own set of very specific standards, namely California, Maine and New York. Additionally, you can check California's Section 177 website to see if your state has adopted any part of the stricter regulations. Below is a general outline of state standards:
| State or Category | Regulation Type | What’s Required for Replacement Cats |
| California | CARB + state anti-tampering | CARB-approved converter with a valid EO, correct application, labels, and warranty/OBD-II compliance. |
| Maine | State adoption of CARB’s aftermarket-cat standard | Maine implemented CARB-level requirements for new aftermarket converters effective June 1, 2015 |
| New York | State-specific aftermarket parts rules | NY regulates aftermarket parts and many “NY-Legal” parts are sold as CARB-exempt/EO-labeled. |
| Other Section 177 states | Adopt CA vehicle standards (varies by rule & model year) | Vehicle standards may be CA-based, but aftermarket cat rules can differ; check state program and CARB’s Section 177 dashboard for current status. |
| All other states (EPA areas) | Federal EPA policy | Use EPA-acceptable replacements and follow anti-tampering guidance. |
Which Catalytic Converter Does Your Vehicle Need?
Use this quick checklist:
- Read your emissions label. If your car is California-certified, you may need a CARB-EO catalytic converter. Otherwise an EPA-acceptable part may apply.
- Match by EO or exact application. CARB keeps EO listings; installers should verify part-to-vehicle fit (make/model/year/engine/emissions family).
- Labeling & warranty. CARB-legal units carry required labels and typically a 5-year/50,000-mile warranty under CARB procedures; federal law provides broader emissions-warranty protections up to 8 years/80,000 miles for certain components.
- Older vs. newer vehicles. OBD-II vehicles (generally 1996+) face stricter CARB compatibility and durability criteria; pre-OBD vehicles follow separate evaluation procedures.
Choose CatalyticConverter.Net For Your Replacement Cat
At CatalyticConverter.net we have thousands of approved parts meeting EPA and CARB standards and have both direct-fit and universal-fit converters to choose from for nearly every make and model.
- We Have Been Selling Online Since 1996
- Our Products Are Manufactured In The USA
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