How the Visible Smoke Test Works

The smoke inspection test for visible smoke was a new assessment added at all Smog Check stations in March of 2008 in California. The new procedure takes at least 20 seconds and is required by the Bureau of Automotive Repair in California, with the specific goal of identifying any visible smoke from the tailpipe or the crankcase area. The regulation is designed to make sure that particulate matter in exhaust fumes is discovered, because it was not being measured under prior regulations. Dangerous particle matter from burning engine oil can cause lung problems for citizens.

By walking you through what a Smog Check technician looks for during just the smoke assessment, you can better appreciate the myriad of details that are involved in every single vehicle check. First, while the engine is idling, the tech goes to the tailpipe and removes the exhaust probe. The tech then watches the tailpipe area for a minimum of 10 seconds. If the tech spots any smoke, he or she must record it as defective under the heading of Other Emission Related Controls.

Secondly, again while the engine is in idle, the tech examines the crankcase/PCV system for smoke for 10 seconds during the liquid leak portion of the test. If smoke emanates from the crankcase, the tech must make a defective notation under the Other Emission Related Controls heading. On the other hand, if no smoke is found from either the tailpipe or the crankcase, the vehicle will receive a passing notation under the Other Emission Related Controls grouping.

It doesn’t matter if there is smoke coming from somewhere besides the tailpipe or crankcase area – the vehicle still gets a passing grade. If the vehicle does not pass, the customer receives an information sheet and documentation of the failing mark. It should be noted that steam is different than smoke, and steam is not a cause for failure of the visual smoke test. However, if a customer disagrees with the results of this visual smoke test, they are welcome to contact a referee for another ruling and second opinion on the matter.

The beauty of this test is that it is economical to perform, because no new measuring devices had to be bought by station owners – the technicians just need to use their eyes to perform this portion of the Smog Check. Yet the test catches dangerous particulate matter, and ensures that the problem is taken care of. It is believed that tens of thousands of vehicles cannot pass the visual smoke test, so this battery of tests will make a big difference in car pollution in California.