Vehicle Emissions Testing

Overview

Growing vehicle use in metropolitan Phoenix and Tucson contributes to air pollution that endangers public health. To improve air quality and reduce vehicle emissions in these areas, the Arizona Department of Environmental Quality (ADEQ) administers the Vehicle Emissions Inspection program (VEIP), a mandatory vehicle emissions testing and repair program. Vehicles in the Phoenix and Tucson areas must pass a vehicle emissions inspection test before being registered with the Arizona Department of Transportation Motor Vehicle Division.

Fuel cap testing is an integral part of ADEQ’s testing program.  Studies have shown that up to 22 gallons of gasoline a year can be lost from a single vehicle’s faulty gas cap, leaking some 137 lbs of evaporative emissions into the air. Prior to 2015, roughly one out of three test failures occurred because of leaking or faulty gas caps. When this happened, the motorist had to leave the testing facility, purchase a new gas cap and return at a later date for a free re-testing of their vehicle. ADEQ now offers a free gas cap replacement program for vehicles that fail the gas cap portion of the emissions inspection.

RESULTS

The gas cap replacement program is implemented at no cost to motorists or the state. ADEQ reports that approximately 50,000 Arizona motorists a year benefit from the program, and as a result of the program, initial test failure rates have been reduced by 45%. In addition, an estimated 3,300 tons of annual evaporative emissions have been eliminated resulting in cleaner air for millions of Arizona residents.