This means that the increased levels of CO2 and CO in the air health hazard. Gas carbon monoxide (CO) is colorless and odorless can be deadly. These combustion gases generated by combustion engines are less than perfect, such as automobile and diesel engines. Often times there have been deaths due to turn on the car with glass-enclosed brackish and car air conditioner is on. CO gas can get into the car if there are any leaks.
Addendum: If the car was stopped a long time, do not ever leave a car that was well lit and air-conditioning turned on. Especially if in it there was a baby. That is very dangerous.