A top Twin Cities hospital is ready to help patients exposed to an invisible threat around the clock.

"You may notice a headache. You may notice a feeling of light-headedness or nausea, or you may not notice anything until it's too late. That is what is so insidious and so dangerous," Dr. Dan Popa said, describing signs of carbon monoxide poisoning.

In November, a dozen people were treated at Hennepin Healthcare for carbon monoxide poisoning. Cases always rise in colder months, with the use of furnaces and people working on gas motors in closed garages.

An hour and a half of breathing pressurized oxygen in a hyperbaric chamber can help rid the patient's blood of potentially deadly carbon monoxide.

The hyperbaric chambers can also be used to treat burns and wounds that don't heal.

"You feel a little refreshed. First, your nerves have to settle down," Thomas Roinestad said after his hyperbaric treatment to help wounds heal ahead of surgery.

A former mechanic, Roinestad has also been treated at Hennepin Healthcare for carbon monoxide poisoning. 

"Fixing cars, one of the exhaust hoses fell off in the garage I was working at," Roinestad said.

Medical staff say the best prevention is to have carbon monoxide monitors in your home, and they actually give one to patients at Hennepin Healthcare.

Doctors at Hennepin Healthcare also say to beware of wellness centers that advertise hyperbaric sessions as a rejuvenating treatment. Misuse of the equipment can lead to a potentially deadly fire.