Emissions Testing in Connecticut

Who Needs an Emissions Test or Smog Check

Most passenger vehicles that are neither exempt by model year nor fuel type must pass emissions testing. Exemptions include vehicles younger than four model years, those older than 25 model years, fully electric vehicles, motorcycles, heavy vehicles over a defined weight threshold, farm vehicles, composite vehicles and certain specialty license plate vehicles. Requirements may vary by vehicle type, and it is best to check official guidance for your situation.

How Often Tests Are Required

Emissions testing is required every two years under the state program. Vehicle owners receive a notification in advance, often at least 45 days before the due date. You may present your vehicle for testing up to 90 days in advance. Late fees apply if you miss the deadline. Specific frequency depends on registration schedules and vehicle class, and regulations may change.

Where Emissions Testing Is Required

Testing is required statewide in Connecticut under the I/M program because much of the state does not meet ozone standards. However, requirements may vary slightly by location due to air quality zones and attainment status. Some urban or more polluted areas may be the focus of stricter enforcement. Regulations may differ by ZIP or town, so it helps to check your address.

What Happens During the Test

Testing typically involves plugging the vehicle into its onboard diagnostics system (OBD II) and may include tailpipe or gas cap pressure leak tests depending on vehicle make, model year and fuel type. A visual inspection of emissions control components may also occur. Technicians check readiness monitors and may perform idle or diagnostic cycles. Emissions testing requirements in Connecticut ensure vehicles meet pollution standards. Failure may require repairs and a retest. The fee applies at the station and results are recorded with the DMV.

Areas in Connecticut That Require Emissions Testing

Requirements differ across cities and towns, particularly where air quality is more at risk. Even though the entire state participates in Connecticut’s vehicle inspection program, emission control is especially critical in denser municipalities such as Hartford, Norwalk, Danbury and East Hartford. Residents of South Windsor, Old Greenwich, Milford, Hamden, Farmington and Manchester also rely on emission inspections. You can search emissions testing locations in Connecticut to find a center near you. Urban areas often have more certified stations and more frequent enforcement, while rural areas may have fewer but still adhere to the same underlying requirements.

How the Emissions Test Works in Connecticut

The testing process takes approximately 15 to 30 minutes at a certified emissions testing station. Visit with your vehicle’s registration and your photo ID, and bring the inspection notice if you received one. First, the inspector confirms vehicle identity, plugs into the OBD‑II port, and reviews readiness status. Depending on your vehicle, they may conduct tailpipe sampling, a gas cap pressure test, or idle diagnostics. Common failure reasons include a check engine light, incomplete readiness monitors, or malfunctioning emissions controls. If your vehicle fails, you have a limited time—often 60 days—to repair and retest. Stations set their own fees for the test and retest; payment is made directly at the site. After a pass, you receive documentation needed for registration renewal.