A. The gas cap exchange program is a strategy to reduce summertime air pollution levels by reducing evaporative emissions. Evaporative emissions play an important role in ozone formation. Ozone is a particularly dangerous pollutant that adversely impacts our health. The Denver metropolitan area also is on the verge of violating the federal health-based standard for ozone. A violation could result in additional, costly regulations.

Q. How do bad/missing gas caps affect ozone in the atmosphere?

A. Your gas cap is an important element of the emissions system on your car. A properly functioning gas cap prevents harmful pollutants from escaping into the atmosphere. These pollutants are a part of the summertime pollution problem in the Denver metropolitan area. Reducing their ability to evaporate and/or escape is an important air pollution control strategy.

Q. Where can I get more information on the ozone problem?

A. Call the Regional Air Quality Council at 303-629-5450, and ask for an ozone information brochure, or visit their website at www.raqc.org.

Q. I am not due for an emissions test any time soon, but I’m concerned about the ozone problem. How can I find out if I have a bad gas cap?

A. Gas cap pressure testing is a pass/fail part of the emissions test. Repair shops in the area that do emissions repairs will most likely have cap testing equipment on hand. Check the Emissions Repair Guide for an emissions repair shop in your area, and call them to see if they can test your cap.

Q. What if I failed an emissions test for some other reason just before the gas cap program starts, and then I come back for a retest and fail for the gas cap?

A. If you failed the emissions test for some other reason, it is likely some repair work is needed to bring your vehicle into compliance with air quality standards. If your gas cap fails, you will receive a replacement or a coupon good toward the purchase of a new gas cap.

Q. Why do I have to take the whole emissions test over again if I’ve failed only for the gas cap?

A. Since the beginning of the program, the procedure has been that no matter what portion of the test your vehicle fails, a complete retest is required. However, the Colorado Department of Public Health and Environment (CDPHE) is considering whether to alter this procedure to allow a quick gas cap retest outside of the normal testing lanes for the convenience of consumers. This would require substantial hardware and software changes in the testing lanes, and would take some time to accomplish. For now, the CDPHE plans to monitor the effect on other elements of the retest for vehicles that initially fail just for gas cap pressure.

Q. How many gas cap failures is the state expecting on an annual basis?

A. Between two and three percent of vehicles fail the gas cap pressure test. That translates to about 20,000 to 25,000 vehicles annually.

Q. What if my car has an unusual gas cap or a locking gas cap?

A. If you have an unusual cap, a locking cap or a tethered cap, you will be given a $5 coupon good at any NAPA retail outlet in the Denver area toward the purchase of a gas cap. After installing your new cap, you must return to the emissions station for a retest.

Q. Who’s paying for the free gas caps?

A. Funds for the $100,000 gas cap exchange program are being provided by Envirotest Systems Corp. and by a federal Congestion Mitigation and Air Quality (CMAQ) program grant, locally administered by the Denver Regional Council of Governments and the Colorado Department of Transportation. NAPA Auto Parts again has agreed to provide the approximately 12,000 gas caps at a reduced cost and will honor the coupons at all area NAPA retail outlets.