Parking on a snowbank and then deciding to let your car warm up, or sitting inside a running snow-covered car, can prove fatal.

Your vehicle’s exhaust contains poisonous carbon monoxide gas and can cause severe injury and even death if inhaled. Obstructing a vehicle’s tailpipe can send the gas right back into your vehicle, and being that carbon monoxide is odorless, you wouldn’t even know.

If your car is stuck in the snow and you have the engine running, open a window slightly and clear snow away from the exhaust pipe.

According to the Centers for Disease Control and Prevention (CDC), more than 400 Americans die each year from unintentional carbon monoxide poisoning not linked to fires, more than 50,000 people visit emergency rooms, and more than 4,000 others are hospitalized.