https://www.amazon.com/Kidde-KN-COP...6652&sr=8-3&keywords=carbon+monoxide+detector I bought the above carbon monoxide detector out of curiosity.. it has over 1,500 positive 5 star reviews. I put it near the exhaust in the mall parking and sit inside for 20 minutes.. but it doesn't seem to detect any carbon monoxide coming from the exhaust. The car is a Honda CRV. Does modern exhaust system have so called catalytic converter that produce almost zero output or is the detector just not accurate enough? But it's supposed to be sensitive to detect minute amount of carbon monoxide. The unit self test seems to work.