Smog certifications for a car can be obtained by taking the car to a service station authorized to run an emissions test and grant a certification. These stations are typically found by checking with the department of motor vehicles for the state. Smog inspections are also often required when a vehicle changes ownership.
After an authorized service station runs an emissions test on a vehicle, it prints off the vehicle's test results; this typically constitutes the smog certification. The smog certificate enables the owner to complete his vehicle registration or sell the car. If a car fails a smog test, it must be repaired until it passes. Each state has a different list of vehicles that are exempt from smog inspections. This list generally includes hybrid cars, electric cars, motorcycles, diesel-powered vehicles and natural gas-powered vehicles.
As of 2014, states that require smog checks every two years include California, Connecticut, New Jersey, New York and Rhode Island. Some counties in Arizona, Colorado, Illinois, Indiana, Maryland, Missouri, New Mexico, Ohio, Oregon, Utah, Virginia, Washington and Wisconsin also require biennial smog checks. Some counties in Georgia, Idaho, Louisiana, Nevada, North Carolina, Pennsylvania, Tennessee and Texas require annual smog inspections. The states of Massachusetts, Vermont and New Hampshire require annual smog inspections.