"Buckwild" star Shain Gandee, 21, died from carbon monoxide poisoning from toxic exhaust fumes, according to news reports.

People magazine reported that Gandee and his companions were found in his car on Monday, which was stuck in the mud. People explains:

With the vehicle knee-deep in mud, toxic fumes from the car were likely unable to escape through the tailpipe, authorities say.

Carbon monoxide is dangerous because it replaces oxygen in the blood, thereby impairing the body's ability to take in oxygen, according to the Mayo Clinic. This can lead to tissue and organ damage, brain damage, and ultimately death.

According to the Centers for Disease Control and Prevention, more than 400 people die every year from carbon monoxide poisoning in the U.S., 4,000 people are hospitalized because of it, and more than 20,000 people visit the hospital because of it.

Carbon monoxide is found in exhaust fumes (like from stoves, certain heating ranges and cars/trucks), and doesn't have any smell or color. Symptoms of poisoning with the gas include feeling tired, dizzy, drowsy, nauseous and having chest pain, according to the Occupational Safety and Health Administration.

A doctor can do a blood test to determine if you do in fact have carbon monoxide poisoning. If you suspect you have been poisoned, it's important to get fresh air as soon as possible. Doctors may treat you with pure oxygen or hyperbaric oxygen therapy (where you're put in a pressurized chamber), according to the Mayo Clinic.

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