Winter storms bring freezing temperatures and power outages — conditions that can significantly increase the risk of carbon monoxide poisoning.

It’s a silent killer responsible for more than 500 deaths every year across the country.

“We see quite a few cases each year,” said Dr. Chris Holstege, medical director of the Blue Ridge Poison Center in Charlottesville, Virginia. “Many of them could have been prevented.”

Carbon monoxide is an odorless and colorless gas produced when fuels, such as wood, gasoline, natural gas or propane, burn incompletely.

During winter storms, people turn to alternative heating sources, including fireplaces.

“We have seen times, people who will start their fireplaces and the flue is blocked by something and they don’t realize it,” Holstege said. “Part of the gas that’s coming from the fire is actually coming into the home, and they get poisoned from that.”

The risk grows during power outages caused by storms.

Many households rely on portable generators to keep lights on, often placing them too close to living areas.

“You can have people who start their generators up somewhere near the home or even inside the home, which is the worst,” Holstege said.

Experts recommend people place generators at least 20 feet away from their homes.

Running cars for too long inside a garage to warm them up can cause similar problems, according to Holstege.

Symptoms of carbon monoxide poisoning include headache, dizziness, nausea and confusion.

Other clues include feeling better when leaving your house or having family members with the exact same symptoms.

Holstege strongly urged everyone to have at least one carbon monoxide detector in their home.

“If you’re only going to get one, I’d have it where the furnace and the hot water heater tend to be, because they sometimes get faulty,” he said. “I have one that’s downstairs in our basement, but I also have one in the main living area.”