Concord, N.C. ? NASCAR approved a carbon monoxide filter Friday to allow drivers to breathe easier during races that can last as long as five hours.

NASCAR’s research has shown that the device, called a catalyst, can reduce carbon monoxide by up to 75 percent inside the car.

“The experts concluded that the levels of carbon monoxide were not at an alarming level,” said Gary Nelson, NASCAR’s managing director of research and development. “But we wanted to ensure our drivers the best possible environment to compete in.”

The device, which will be optional, has been one of the top projects at NASCAR’s research and development center. It costs around $400 to build and can be installed in a car in about two hours.

NASCAR has identified one manufacturer for the catalyst and is looking at other designs to be used in the driver’s ventilation system.

The catalyst sits on the floor in the car next to the driver and sends clean air to the driver’s helmet. It’s the same theory as catalytic converters used in street cars to diminish pollutants in the exhaust, “but this is a low-temperature catalyst.”

NASCAR has been working since last fall on systems to filter the air a driver breathes during a race, a project that drew increased focus after Rick Mast announced in January he was retiring because years of exposure to toxic fumes had given him acute and chronic carbon monoxide poisoning.

The effects of carbon monoxide are cumulative, building in a driver’s body each time he or she is exposed to it. Since last year, some drivers have been undergoing heavy oxygen treatments after races to decrease the effects of breathing carbon monoxide.