Exhaust fumes are extremely dangerous and can seriously injure and even kill people who are exposed. Exhaust fumes from heaters, for example, contain carbon monoxide, which is regarded as the commonest single cause of poisoning in both industry and the home.

Carbon monoxide is produced when fuels such as gas, oil, coal and wood do not burn fully. Burning charcoal, running cars and the smoke from cigarettes also produce carbon monoxide gas.

“Driving a vehicle with the unfixed problems produces CO, which will disperse into the surrounding areas. But when the vehicle is idle for a long time, CO may re-enter the vehicle, and it is inhaled by the driver or passenger.” “Any leaks in the exhaust system can result in accidental CO poisoning.

Carbon monoxide can come from any source that burns fuel. Common sources are cars, fireplaces, powerboats, wood stoves, kerosene space heaters, charcoal grills, and gas appliances such as water heaters, ovens, and dryers. Usually they cause no problems. Even sitting in an idling car in an open garage can be dangerous.

It is dangerous to sit inside a locked car. It is even more dangerous when the air-conditioning is on. Car exhaust emits carbon dioxide and carbon monoxide gases (in case the AC is on) that might kill an adult instantly. “If you sit inside a locked car for 30 minutes, you would feel suffocated.

Cars, trucks, or other engines are left running in enclosed spaces, such as garages. Carbon monoxide can build up in a garage and leak back into the house. Even sitting in an idling car in an open garage can be dangerous.

How much is dangerous? High concentrations of carbon monoxide kill in less than five minutes. At low concentrations it will require a longer period of time to affect the body. Exceeding the EPA concentration of 9 ppm for more than 8 hours is suspected to produce adverse health affects in persons at risk.

Thomas Greiner, an extension agricultural engineer from Iowa State University, has this warning. “Don’t ever warm-up a car in a garage, even with the garage door open. In less than two minutes gas fumes build to lethal concentrations in the garage.” In an attached garage, fumes can quickly spread to the house.

Ray: Well, to answer your first question, leaving the car running all day won’t do any damage. As long as the engine’s cooling system is working normally, a modern car can run for days and days — until it runs out of gas — without causing itself any harm.

In the end, leaving your car idle for 30 seconds to a minute can do it no harm. Technically, letting it run idle longer will not cause much harm, either. However, keep other aspects of doing so in mind. Letting the engine run for no reason is a hazard to the environment.

Research has revealed that sleeping in a car with the AC running can be fatal due to carbon monoxide poisoning. Carbon monoxide reduces the blood’s ability to carry oxygen to your cells and causes them to die due to short supply or lack of oxygen, which can lead to brain damage and ultimately death.

The dangerous part about sleeping in the car is that a person may die in their sleep due to carbon monoxide poisoning without ever experiencing symptoms.