Pop quiz: You’re sitting at home when you notice you have a dull headache. You suddenly start to feel dizzy, weak and nauseous. Do you close your eyes to take a nap — or would you recognize the symptoms of carbon monoxide poisoning and get out of the house ASAP?

Related: Carbon Monoxide Poisoning: Is Your Family Protected?

If you’d recognize the symptoms you’re in the minority, according to a recent survey from Service Experts Heating and Air Conditioning. The survey found:

  • About two-thirds of people surveyed said they didn’t know if they would recognize the symptoms of carbon monoxide poisoning.
  • More than half of homeowners aren’t aware a clothes dryer can be a source of carbon monoxide, and a quarter of them didn’t know the fireplace also can be a source. (So can portable generators, hot water heaters , kerosene or gas space heaters and other appliances.)
  • More than half didn’t know the best place to install a carbon monoxide detector.
  • Over one-third of homeowners didn’t know if they have a carbon monoxide detector.
  • More than half don’t get their furnace checked each year. An inspection can identify leaks and potential leaks.

What you don’t know about carbon monoxide can kill you.

Carbon monoxide is a colorless, odorless gas that can build up in the air if an appliance is leaking and poison the people and animals who breathe it. It’s found in the fumes produced when you burn gas, wood, propane, charcoal and other fuel in stoves, lanterns, grills, fireplaces, gas ranges, or furnaces, according to the Centers for Disease Control and Prevention (CDC).

Carbon monoxide poisoning symptoms

They’re often described as “flu-like” and include:

  • Headache
  • Dizziness
  • Weakness
  • Upset stomach
  • Vomiting
  • Chest pain
  • Shortness of breath
  • Blurred vision
  • Confusion

If you’re sleeping when you’re exposed to carbon monoxide, you could die from CO poisoning before you realize anything’s happening, which is why having CO detectors in your home is critical.

More than 400 people die from unintentional carbon monoxide poisoning (not linked to fires) in the United States each year — many of them in the winter months — the CDC says. More than 20,000 go to emergency rooms, and more than 4,000 are hospitalized.

If you think you’re suffering from carbon monoxide poisoning, act right away. Turn off fuel-based appliances and get everyone out of the house. Call 911 or go to an emergency room and say you suspect CO poisoning.

Related: Home Safety Checklist: What to Do When

Prevention at home

UL advises installing a UL-certified CO alarm outside each sleeping area and on every level of the home, including the basement. Avoid placing an alarm directly on top of or across from fuel-burning appliances.Test the alarms monthly and change the batteries twice a year when you change the clocks.

In addition, have your fuel-burning appliances including your furnace, water heater and stove inspected and serviced by a professional once a year. Have your chimney checked or cleaned every year as well.

One final note: Never turn on your oven or gas range to heat your living space. If the power’s out and it’s too cold, seek shelter elsewhere.

Recent legislation

Last year, New York enacted carbon monoxide alarm legislation that requires all commercial buildings (new and existing — including schools, offices and restaurants) with a potential CO source to install a CO alarm. By June 27, 2016, all such buildings must have CO detectors installed and operational.

Angela is a Pulitzer Prize-winning digital editor with more than 15 years of experience delivering news and information to audiences worldwide. Prior to joining SafeBee, she was the features editor for Boston.com at The Boston Globe, overseeing health, travel, entertainment, business and lifestyle coverage. Before moving to features, she was the news and homepage editor, covering stories such as the Boston Marathon bombing, Red Sox World Series victories, presidential elections, a papal inauguration, and more. Her favorite safety tip: Clean your phone! The average cell phone has 18 times more germs than the toilet handle in a men’s restroom.