Emissions Testing in Oregon

Who Needs an Emissions Test or Smog Check

Not all vehicles require emissions testing in Oregon. In 2025 requirements apply only in certain metropolitan areas. Most gasoline, hybrid and alternative fuel vehicles of certain model years must test if registered in those areas. Heavy‑duty diesel vehicles, motorcycles, trailers and vehicles outside testing boundaries are generally exempt. Specific rules vary by location and vehicle type.

How Often Tests Are Required

In areas where testing is required, Oregon mandates it every two years. Vehicles must receive and pass a test before renewing registration in covered areas. If your vehicle is exempt, there is no emissions test requirement. Always refer to official guidance for the current schedule.

Where Emissions Testing Is Required

Emissions testing is required only within specific testing boundaries, notably Portland and Medford metro areas. Vehicles registered elsewhere in the state are not required to test. Requirements may vary by registration zone. Checking the official boundary lookup is essential to confirm whether a vehicle needs testing.

What Happens During the Test

When an emissions test is required, the process depends on vehicle age. For model year 1996 and newer vehicles, an OBD‑II diagnostic scan is used to check emissions systems. Older vehicles may be subject to tailpipe testing where emissions are measured directly. Technicians check the On‑Board Diagnostics readiness monitors and may visually inspect emissions equipment. If the Check Engine light is illuminated, the vehicle will likely fail. Results determine eligibility to renew registration.

Areas in Oregon That Require Emissions Testing

Emissions testing requirements vary across Oregon. Only certain urban areas fall within mandatory testing boundaries. Emissions testing locations in Oregon include Clean Air Stations and private testing providers in regions such as Portland, Medford and adjacent zones. Cities like Hermiston, Portland, Tigard, Corvallis, Eugene, Hillsboro, Klamath Falls, Clackamas, Grants Pass and Gresham may have listings for testing stations, but not all these areas require testing. Only those within DEQ‑defined boundaries must comply. For example Portland and Medford areas have active programs. Outside those zones, stations may serve vehicles voluntarily or for out‑of‑state requirements but testing is not mandated. Always verify whether your area requires testing by using official state boundary tools or checking with DEQ.

How the Emissions Test Works in Oregon

The emissions testing process typically takes between 15 and 30 minutes, depending on factors such as wait time and vehicle type. You should bring your vehicle, your DMV registration renewal form (completed and signed), and valid ID. At the station, your vehicle undergoes either an OBD‑II scan or tailpipe test depending on age. Technicians check diagnostic codes, readiness monitors, emissions equipment and the Check Engine light. Common failure reasons include a lit Check Engine light, incomplete readiness monitors, or emissions system faults. If your vehicle fails, you receive a report and must have repairs completed before retesting. Costs vary by station and include test and, where applicable, registration fees. After passing, you receive a certificate valid for 180 days that allows you to renew your registration without needing another test for two years.