My truck doesn't have an automatic off for the air recycler so when I forgot to shut it off, I developed symtoms of poor judgement, chest pain, nausea, migraine headache, loss of appitite. I started to feel better after away from the truck. I noticed the button was on at the end of my day and night 20 hours later. I thought I had the flu (usual misdiagnosis) and asked for a sick day. This is the first time this happened to me. Long enough exposure I'd be dead. Does your truck have an automatic - off for your air recycler? Do you use an carbon monoxide detector?