Sorry guys. We've all got hectic schedules and plenty of stressors in our lives, but we're about to add one more thing to worry about to your list: Carbon monoxide poisoning. It may sound like one of these urban legends that you read about on the internet, but don't actually know anyone who has experienced it in real life — however, the truth of the matter is that carbon monoxide poisoning is not a myth.

Known as the "silent killer" because it is colorless and odorless, carbon monoxide (or CO) can leak undetected in any home — and though all humans and animals are susceptible, fetuses, infants and people with chronic heart disease, anemia, or respiratory problems are at the highest risk.

According to the Centers for Disease Control and Prevention, this potentially deadly gas can be found in fuel-burning fumes produced by cars and trucks, small engines, grills, lanterns, stoves, gas ranges, fireplaces or furnaces. When carbon monoxide builds up indoors, and when it’s inhaled by a person or animal, it quickly becomes dangerous.

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According to the CDC, unintentional carbon monoxide poisoning causes about 500 deaths per year. This number may not seem as dramatic as the sky-high car crash and gun stats we see circulated on Facebook, but carbon monoxide deaths can be jarring because they are so unexpected — and so easy to prevent.

Carbon monoxide risk heightens in certain high-risk situations — for example, as the weather gets colder and we turn on our furnaces or when we leave the engine running. Understanding the risks and recognizing subtle signs can help to ensure that this preventable accident doesn’t happen to you.

Early warning signs

The early warning signs of carbon monoxide poisoning can easily be confused for feeling under the weather, which is why Dr. Daniel Rusyniak, medical director of the Indiana Poison Center at Indiana University Health, keeps his top red flags short and sweet:

  1. Headache is the most common symptom and is often accompanied by nausea.
  2. Feeling short of breath (like you just ran up a flight of stairs) can be accompanied by chest pain.
  3. Feeling foggy, confused or light-headed.

If you experience one or more of these “unexplainable” symptoms, Rusyniak advises:

  1. Go outside immediately and see if your symptoms improve. Common sources of carbon monoxide exposure include gas furnaces, gas-powered generators, gas-powered space heaters (e.g., kerosene) and operating gas-powered equipment indoors (e.g., power-washing your basement).
  2. If you have a gas furnace, call the fire department to come and test your house for carbon monoxide.
  3. If you are running a gas-powered space heater or equipment, turn them off.
  4. If your symptoms are severe or if you don’t quickly or completely recover (within five minutes), then call 911 and go to the local emergency department.
  5. If you have questions about carbon monoxide or its symptoms, call your poison control center at 800-222-1222.

Advanced warning signs

Dr. Nicholas Kman, an emergency medicine physician at The Ohio State University Wexner Medical Center, agrees with Rusyniak’s assessment of the carbon monoxide basics — a headache is the most common symptom of carbon monoxide poisoning that is “largely variable and nonspecific,” making it very difficult to diagnose.

“As folks get sicker (severe poisoning), we can see altered mental status, confusion, loss of consciousness, seizures and coma. People can also get heart trouble (myocardial ischemia) — loss of consciousness, vomiting and confusion,” Kman explains.

For more advanced warning signs of carbon monoxide poisoning, the same rules apply: Get outside as quickly as possible to escape the source of the leak and call 911 immediately. More severe symptoms should not be ignored since long-term effects of carbon monoxide exposure may not go away on their own.

How to prevent carbon monoxide poisoning

Carbon monoxide poisoning may come on without warning, but there are a few common-sense practices you can use to greatly minimize your risk:

  • Install a battery-operated CO detector in your home and replace the batteries each spring and fall when you change your clocks. Rusyniak says, “[Carbon monoxide] is only detectable by carbon monoxide monitors. Because of this, everyone should have a CO detector on each floor of their house. If it goes off, leave your house and call your local fire department to investigate.”
  • Have your water heater, heating system and any other oil-, gas- or coal-burning appliances checked and serviced each year.
  • Never use a charcoal grill, generator or charcoal- or gasoline-burning device in your garage, basement or home or near an open window.
  • Never leave a vehicle running in an attached garage, even with the garage door open.
  • Never use a fireplace or stove that is not vented.
  • Never use a gas oven to heat your house.
  • See a doctor right away if you experience any of the early symptoms of carbon monoxide poisoning.

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For Mark Schneider, owner of Pacific Aire, Inc. — a heating and air contractors company of in Ventura, California — an annual furnace checkup is a big sticking point. This major risk factor is one Schneider sees often in his line of work, where problems are created when furnace coils wear down and eventually crack the heat exchanger to create a carbon monoxide leak.

Schneider says, “We recommend having a licensed HVAC technician clean and inspect your furnace once a year to be sure you are not at risk. The difficulty in finding these cracks is that the coils twist and turn, and without the proper tools, a tiny crack can become a bigger problem that can go undetected by an untrained eye.”

Originally published January 2016. Updated August 2017.