Cold air intake: UK vs US vs Germany
An intake sits before the engine, so it does not touch the emissions system directly. Whether that makes it a non-event depends on whether the market regulates intake noise and induction certification.
The verdict is not the same in all three markets, so the column that matters to you depends on where the car is registered.
| Market | Verdict | The rule that decides it |
|---|---|---|
United Kingdom DVSA / GOV.UK |
Legal | Legal, emissions system untouched The car must still pass its emissions test, so keep the mass-airflow sensor and related sensors working. No specific check exists for the intake itself. |
United States EPA, NHTSA and state codes |
Conditional | CARB EO needed in California and CARB states It must not defeat any emissions control. Outside CARB states a non-emissions-defeating intake is generally fine. |
Germany StVZO / KBA |
Conditional | Panel filters fine, open induction needs a certificate A drop-in filter in the standard airbox changes nothing. Open induction kits change intake noise and sometimes emissions behaviour, so they need a certificate plus a change inspection. |
The UK is the only outright legal answer in this set, because it regulates neither the intake nor its noise separately. California and Germany both effectively require a certificate.
Why the answers differ
Is a cold air intake legal?
An intake sits upstream of the engine and does not touch the emissions system, which is why the UK reaches an outright legal verdict, the only one in this row. The other two markets object on grounds the UK does not regulate. California and the CARB states require an exemption order because an intake changes the metered air path and therefore is treated as emissions-relevant until proven otherwise. Germany objects on noise, distinguishing a drop-in filter in the standard airbox, which changes nothing, from an open induction kit, which changes intake noise and needs a certificate plus an inspection. The common thread across all three is that the mass-airflow sensor and its calibration must keep working, since that is where an intake actually causes emissions trouble.
Verdict at a glance
The same three markets, grouped by where they land.
Legal
LegalUnited Kingdom. No approval step and no conditions worth planning around in this market.
Conditional
ConditionalUnited States and Germany. Permitted, but only once the condition in the table above is met.
Sources
Primary legislation and regulator guidance behind each market's verdict.
- UKModifying your vehicle's emissions (GOV.UK)
- UKMOT inspection manual: cars and passenger vehicles (GOV.UK)
- USAftermarket, performance and add-on parts (California Air Resources Board)
- USTampering and aftermarket defeat devices (US EPA)
- Germany§ 19 StVZO - Erteilung und Wirksamkeit der Betriebserlaubnis (gesetze-im-internet.de)
- Germany§ 47 StVZO - Abgase (gesetze-im-internet.de)
- Germany§ 49 StVZO - Geräuschentwicklung und Schalldämpferanlage (gesetze-im-internet.de)
Other cross-market comparisons
This is a comparison of national rules, not legal advice for your vehicle. Rules change, and the US row in particular summarises federal law where one exists and the common pattern across states where it does not. Confirm the position in your own state or region before you buy or fit anything. Sources last reviewed July 2026.