We all need to heat our homes when the temperatures drop, but there's a right and a wrong way to do it. Carbon monoxide is an invisible, odorless gas produced by fuel-burning heating systems and it can kill. Dr. Stephen Meldon, an emergency room doctor at Cleveland Clinic, says you need to be vigilant about keeping carbon monoxide out of your home.

"Anything that burns produces carbon monoxide so big no-no's - propane heaters inside, we've heard reports of people using charcoal grills. Those produce a lot of carbon monoxide so I would absolutely discourage that," he said.

According to the Centers for Disease Control and Prevention, carbon monoxide kills about 500 people each year and at least 15,000 suffer from accidental exposure - most from heating systems. It's recommended you have your furnace professionally serviced each year and install working carbon monoxide detectors in your home.

If you fear you have been exposed to carbon monoxide, Meldon says symptoms often mimic the flu.

"The first is really headache, nausea, some confusion, so if you really have any of that I think you really need to get evaluated," warned Meldon.

Portable gasoline-powered generators also produce dangerous levels of carbon monoxide and the CDC recommends they be used outside, far away from your home during a power outage.