OXFORD, N.C. --- Dill Air Controls Products is recalling 1.8 million replacement snap-in rubber valve stems sold between November 2006 and July 2007, the National Highway Traffic Safety Administration announced.

According to the NHTSA, these valves may lack the required additive to protect the rubber against deterioration from ozone exposure. As a result, the valve stems may weather and crack earlier than normal when they're exposed to high levels of ozone.

"Over time, such a crack could progress to the point that it leaks air, resulting in a loss of tire pressure," the NHTSA said. "Loss of tire pressure can result in a flat tire and/or loss of vehicle control, which could cause a crash without warning."

Dill will notify owners and replace the affected valve stems free of charge. The recall began this week. Owners can contact Dill at (888) 364-2982 or visit www.tirevalverecall.net.