California Air Resources Board

This site helps owners of vehicles respond to a Notice to Submit to Testing letter issued by CARB Enforcement under HD I/M.

To help you get your vehicle tested, here is a link to a list of commercial CARB-credentialed HD I/M Testers with contact information: 

• Credentialed HD I/M Tester Public List

Alternatively, HD I/M allows a vehicle owner or a fleet mechanic to conduct the testing and reporting that is required. A tester needs to take the HD I/M training, pass the exam, and use the correct test equipment, as follows:

• Free on-line HD I/M Tester Training course and exam

Test Equipment for engine model year 2013 and newer:

• Carb-Approved On-Board Diagnostics (OBD) Test Devices

Test Equipment for engine model year 2012 and older:

• CARB-Approved Smoke Opacity Meters

If you are submitting a smoke opacity test for your 2012 or older model year engine, you must also submit a completed HD I/M Vehicle Emissions Control Equipment Inspection Form:

• Vehicle Emissions Control Equipment Inspection Form

If your vehicle needs repair to demonstrate HD I/M compliance, you must submit a completed Demonstration of Compliance form (click link below) and send copies of repair receipts.

• Demonstration of Compliance Form

If you are having difficulties finding a HD I/M Tester or procuring testing equipment, please contact CARB Enforcement

Return to Heavy-Duty Diesel Inspection & Periodic Smoke Inspection Programs