Emissions Testing in Tennessee

Who Needs an Emissions Test or Smog Check

Most vehicles in Tennessee are not subject to emissions testing. Only in limited cases, such as registration in a county that has chosen to reinstate a program under federal air quality rules, might testing be required. In those rare cases, requirements would apply to gasoline or diesel vehicles meeting model year criteria and weight thresholds. Requirements may vary by vehicle type, fuel, age, or regional designation. Always consult official state or local sources for current criteria.

How Often Tests Are Required

Where testing does occur, it generally follows a schedule tied to registration or renewal, often annual or within a defined window before registrational deadlines. Since most of Tennessee has no testing requirement, frequency is not uniform statewide. In limited reinstated zones, frequencies mirror prior programs and may vary. Check local regulations.

Where Emissions Testing Is Required

Emissions testing requirements in Tennessee currently apply to very few areas. Davidson County ended its program in February 2022, and no other counties require testing. Requirements may vary if local air boards reinstate testing, but at present no urban or rural area in the state has mandatory testing. Always confirm with local authorities.

What Happens During the Test

Where a test is required, the process typically includes an On‑Board Diagnostics II scan, visual inspection of emissions equipment, catalytic converter and gas cap checks for newer vehicles, and tailpipe or traditional testing for older models. A scan tool reads readiness monitors and malfunction indicators. If the check engine lamp is illuminated or monitors are incomplete, the vehicle can fail. Technicians look for emissions equipment integrity and system codes. Testing stations issue certificates when vehicles pass. Specific procedures may vary by station.

Areas in Tennessee That Require Emissions Testing

Requirements differ across Tennessee based on local decisions. As of now no major cities including Knoxville, Chattanooga, Nashville, Memphis, Murfreesboro, Clarksville, Cookeville, Columbia, Madison or Sevierville have active emissions programs. Testing is effectively optional or not required across the state. For residents prompting out‑of‑state registration or unique air quality needs there may be use of emissions testing locations in Tennessee, but these are not mandated. Always confirm with local environmental or motor vehicle authorities.

How the Emissions Test Works in Tennessee

When testing does occur the process generally takes about 15 to 30 minutes. You bring vehicle registration, title or bill of sale, inspection packet if applicable, and personal identification. At the station you check in, then technicians perform a visual inspection, OBD‑II scan, gas cap or catalytic checks, and tailpipe analysis if needed. Common failures include illuminated check engine lights, incomplete readiness monitors, missing emissions equipment, or visible tampering. If your vehicle fails you can have repairs done and return for a retest. Costs vary by location and station. Certifications are issued upon passing; if you fail you receive guidance on needed repairs.