Rick Mast is retiring from auto racing after suffering from acute and chronic exposure to carbon monoxide poisoning. He raced in 9 Cup races last year before he stoped driving because of his illness.
Some of you younger guys might not rememeber this but Richard Petty used to drive with mask, similar to what jet pilots wear. It was funny looking at him when he was driving. Made him look like he was heading out for a bombing run. Before that, he would always have a towel in him mouth. I don't think that had anything to do with the carbon monoxide though.