How are people poisoned by carbon monoxide?

Treacherous: I trust you are not a smoker. A faulty home heater can kill an entire family in their sleep. An old automobile without a catalytic converter can kill a would-be garage suicide as well as his family in the adjacent rooms. Faulty engines in airplanes are infamous. Using the barbecue indoors is a very bad idea. Do not go back into a burning building.