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Is a Cold Air Intake Legal in the US?

Conditional

A cold air intake is legal in most of the US, but California and the CARB states require it to carry a CARB Executive Order (EO) number. Anywhere it must not disable or trick the vehicle's emissions sensors.

Why?

An intake changes how the engine draws air, which can affect emissions, so it falls under the aftermarket-parts rules. In the 30-plus states that do not follow CARB, a quality intake that keeps the emissions system working is generally street-legal.

In California and the states that have adopted CARB rules, the bar is higher: an intake needs a CARB Executive Order (EO) to be legal on the street, and many popular intakes carry one. Fitting a non-EO intake in a CARB state can fail a smog check even if the car runs fine.

Either way, the intake must not defeat emissions equipment or throw the fueling out so far that it raises emissions. Check for a CARB EO if you are in a CARB state; elsewhere, a properly working intake is usually fine.

What decides if it's legal

  • A cold air intake must not defeat any emissions control.
  • In California/CARB states it needs a CARB EO number to be street-legal.
  • Outside CARB states, a non-emissions-defeating intake is generally fine.
  • Keep the mass-airflow sensor and related sensors working correctly.

Does it depend on your state?

Yes. In CARB states the intake needs a CARB EO to be street-legal; in non-CARB states an emissions-neutral intake is generally allowed. The part is the same; the state decides the paperwork.

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Sources

This page is general guidance, not legal advice, on the rules in the US for cold air intake. The detail varies by exact vehicle and changes over time - confirm with your insurer and the EPA, NHTSA and your state DMV before modifying.