In 1970 Congress passed the Federal Clean Air Act, which set quality standards for the nation. The act required areas that did not meet air quality standards to implement emissions control strategies or they would lose their building and highway funds. California did not meet the Federal Air quality standards. Hence, in 1982 it decided to implement an emissions inspection program, currently referred to as the "Smog Check" program.
The California Smog Check program and California's emission laws are designed to identify vehicles, which are polluters through the use of an exhaust gas analyzer for 1999 & older model vehicles.
The exhaust analyzer is much like a photo camera except it takes pictures of your vehicle's exhaust (rather then your vehicle) and translates that into information which a Smog technician can read/understand and evaluate. Based on this information the technician can diagnose your vehicle's engine condition.
2000 model year & newer vehicles are tested via DAD OIS system which includes a visual smog check inspection and functional inspection for OBD II trouble codes and readiness monitors. 2000 & newer vehicles are not administered the tailpipe exhuast sample portion of the smog inspection process.
The Smog Inspection is not to be feared. It's simply an inspection designed to make sure your car is in good running shape. It's also an excellent opportunity for you to evaluate your vehicle's engine performance and make sure your car is running at optimum levels.
Price of the smog check - The State of California does not regulate the cost of the smog check. The price of a smog inspection will vary from one smog test center to another. Smog stations are privately owned businesses. The normal price range of the average smog test is between $29.95 and $69.95 depending on the county you live in, the type of vehicle you own. car, truck, van, SUV, or motorhome, and the type of smog inspection your vehicle requires.
This price may or may not include the California Emissions Certificate Fee of $8.25, or any additional fees the smog station may be charging for your vehicle's specific smog inspection.
If you're a bit intimidated, don't be. There are strict laws which require smog stations, smog test only centers and smog repair centers to display their smog inspection prices in areas accessible to and easily viewed by the public.