Starting Tuesday, if a car fails the test because of a leaking gas cap, a new one will be provided for free at the testing center.

In the past, car owners have had to leave the testing center to buy a new gas cap at an auto supply store, and then get another emissions test. The testing center was required to conduct the retest for free.

The Arizona Department of Environmental Quality worked with Gordon-Darby, a private company that conducts all emissions tests for the state, to eliminate the need for a second trip to the testing center.

State officials say distributing gas caps at the testing point will save car owners time and hassle, and will save Gordon-Darby the cost of conducting a second test.

Regular gas caps sell for up to $15 and the contractor will cover the cost.

Beth Gorman, public outreach and education manager with the Pima County Department of Air Quality, said she welcomes DEQ’s newest program.

"Motor vehicles are a major source of air pollution in our community," Gorman said. "So anything that we can do to reduce emissions from these vehicles is going to help our air quality. Gas caps can leak gasoline fumes, which wastes gas, but those fumes also combine in the presence of other pollutants and solar radiation to form a very dangerous pollutant called ground level ozone.”

Each year, nearly 75,000 cars in Arizona fail emissions because of leaking gas caps.