working with carbon monoxide expert tom firesign. the bayshore fire department there to keep us safe. the car a 2013 chrysler 300 one of many on the market with keyless ignition and no automatic shutoff. this garage freestanding. we covered the exterior vents to mimic what could happen with many attached garages. after our producer exits the car without shutting it off, he hears no alarm outside the vehicle. we leave the car running. then a check every 30 minutes for the level of carbon monoxide. 2 1/2 hours into our demonstration, co levels are rising quickly. >> we're currently at 890 parts per million. and that could be potentially lethal. >> reporter: then at almost 4 1/2 hours in the co level is at 4,350 parts per million. lethal levels. >> if you were to go inside this garage right now and close the door you would probably lose consciousness within five to ten minutes, and death would follow shortly thereafter. >> reporter: at this point the fire department too worried about the danger to continue. so we stopped the demonstrati