TAMPA, Fla. – About 400 people die from carbon monoxide poisoning every year in the United States.
While carbon monoxide poisoning cases spike in the northern states during the winter because home heaters are on full blast, it's a danger everywhere year-round.
Many victims don't know they're affected until it's too late.
Cathy Gunn didn't know driving her van into the garage could lead her down a deadly road.
"I was going to die. Going to die," Gunn said.
After Gunn's keyless van was accidentally left on, carbon monoxide seeped out of the exhaust pipe and found its way into her home.
"The whole house had filled to a 190 level. Usually at 200, they (first responders) see people unconscious or dead," Gunn shared.
Gunn had no idea she was breathing in the poison for hours. Somehow she made it out alive. But the poison was still creeping its way through every corner of her body.
"I told my husband, 'I'm gonna die.' Take all the money out of the bank, and fly me anywhere in the world but get me help now," Gunn said.
Help came in the form of hyperbaric oxygen therapy.
Gunn lay inside the pressurized chamber, breathing in 100 percent oxygen, three hours a day, for 43 days.
"It accelerates the elimination of carbon monoxide," said Dr. Surbhi Jain, of AdventHealth.
Jain said the therapy also eliminates the hyper activation of white cells.
"So the injury damage that is happening in the body at the cellular level is what the hyperbaric acts upon," Jain said.
"The hyperbaric oxygen therapy definitely saved my life," Gunn said.
Gunn said she does not park a keyless car in her garage and advises others to do the same.
Carbon monoxide comes from gas burning in poorly ventilated areas.
Jain said carbon monoxide detectors can detect when levels are too high and should be installed in homes in addition to smoke detectors.