About Five Rivers Smog

Five Rivers Smog is a mobile emissions testing company that specializes in the California Air Resources Board (CARB) Heavy-Duty Inspection and Maintenance program, also known as the Clean Truck Check. We are an HD/IM certified tester, which means we are authorized to perform official emissions inspections on heavy-duty vehicles and to submit the results electronically to CARB's database on your behalf, in real time.

This service is built for the people who keep freight moving: fleet managers, owner-operators, and trucking companies that run diesel or alternative fuel vehicles over 14,000 pounds GVWR on California roads. That covers semi trucks, box trucks, tow trucks, buses, and motorhomes, including out-of-state vehicles that travel through California. When a truck is out of compliance, it cannot legally operate, and every day it sits is a day of lost revenue. Our job is to keep that from happening.

We are based in the Central Valley and travel within a 20-mile radius of Stockton, testing vehicles at your yard, terminal, or on the roadside, 24 hours a day and 7 days a week. Because we come to you, your equipment never leaves service for a trip to a testing station.

This website is built and maintained by the same certified testers who run the inspections. It was created as a simple place for California fleet operators to understand what the Clean Truck Check requires, confirm their vehicle class, see the area we cover, and reach dispatch at any hour. Every inspection we perform is backed by a free retest guarantee: if a vehicle does not pass on the first attempt, we retest it at no additional cost.