States have different requirements when it comes to smog testing, and their terms and exemptions can vary. For example, in California, most vehicles that are more than six years old must be tested every two years, but gas-powered vehicles built before 1975 are exempt from testing.

How often are emission tests required?

Vehicles driven in California are required to have an emissions test every two years. Drivers who fail to have their car, truck, or SUV smog-checked will not be allowed to register their vehicle.

How long is the validity of emission test?

Question: How long is the car emission test validity? Answer: One year. The LTO requires an emission test every time you register it.