The Dangers of Carbon Monoxide When an exhaust pipe exits directly to the rear of a vehicle, highly poisonous carbon monoxide gas may be drawn into the rear compartment. Even a slight opening or faulty gasket can allow significant exhaust fumes in. Check and replace seals regularly. This becomes even more dangerous when a side window is open which draws even more carbon monoxide gas inside. This applies also to vans, SUVs and station wagons. Rear exit exhaust systems should only be installed on pickups without camper shells or where camper shells are never used to carry people or animals. If you tow a trailer or carry passengers inside a camper shell in the back of your truck, you should select a single or dual side exit system. With rear exits you may find exhaust soot on the trailer you’re towing. And if you carry passengers in the back, you run the risk of carbon monoxide poisoning.