CO Poisoning: The Hidden Danger of Emergency Heaters

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I previously wrote about how to survive a winter storm at home in case your power goes out, which has some great overall information in it to help you prepare, but I realized I’d missed something important and thought I should address it in its own post – the danger of carbon monoxide (CO) poisoning and what you absolutely need to know about it.

A few days ago, Colorado hit the lowest recorded temp in the continental US in history at -32F. We’ve also had a couple of really bad storms blow across the US already this winter and several people have died. In many emergencies, such as this, you need to rely on emergency heating, and if you don’t have the right heater or setup, there is a real danger of getting carbon monoxide poisoning.

Carbon Monoxide (CO) vs. Carbon Dioxide (CO2)

So a lot of people first get a little confused because they think CO is harmless because that’s what we breathe out, right? Actually,  no. We breathe out carbon dioxide (CO2), not CO. CO2 is what plants use to convert to sugar and oxygen during photosynthesis and is a by-product of complete combustion (burning). CO is a by-product of inefficient burning and is extremely dangerous.

According to the CDC, over 400 people die in the US alone every year and over 50,000 people go to the emergency room for CO poisoning. One note here, the death rate around the world is MUCH higher than that, due to hospitals here being able to recognize and test for it so they can treat people before it’s too late.

Your body can take in a lot of CO2 so even though it’s not impossible for it to be dangerous, it’s extremely rare. CO, on the other hand, does bad things to your body. I’m not going to go into deep scientific detail here since most of you just want to know what the danger is and what you can actually do about it but essentially, CO binds with the hemoglobin of your blood easier than oxygen does, so it basically starves your body of oxygen.

It’s so effective that CO poisoning is a very popular method of suicide around the world, in no small part due to the inaccurate representation of it being portrayed in the media as being painless. It’s not, btw. Here are some common symptoms:

  • aches and pains
  • headaches
  • weakness
  • nausea or vomiting
  • chest pain
  • shortness of breath
  • dizziness or lightheadedness
  • balance problems
  • memory problems
  • unconsciousness

There are more bad things it does to your body but they’re much more technical. If you want some of that good ol’ sciency stuff, read this.

Basically, CO2 = good, CO = bad.

What Heaters Cause CO Increases?

Basically, any heater that burns something (coal, propane, whatever), can cause CO output and put your life in danger. This includes:

  • fireplaces
  • wood stoves
  • gas appliances
  • kerosene heaters
  • charcoal grills
  • oil, propane or gas furnaces

Basically, if it burns some kind of fuel and isn’t properly ventilated to the outside world, it can be a problem. The heaters listed above are most likely safe, as long as you have some sort of sensor to tell you in case of a leak.

How to Safely Heat Your Home in an Emergency

The simple answer would be to just use something that doesn’t produce CO but that’s not always practical, especially in an emergency.

There are essentially two ways to increase the safety of using an emergency heater (or any heater) indoors: use a heater that doesn’t produce large amounts of carbon monoxide, or try to ventilate one that does and use some kind of sensor or alarm to tell you if the CO is rising to dangerous levels.

Here are some heaters that don’t produce CO to large amounts indoor:

  • electric space heaters
  • oil-filled heaters that do not burn oil (which are typically electric)
  • sealed, ventilated units that send or keep all gases outside
  • catalytic heaters such as the Mr. Heater*

*Just a quick note, I spent a year living on a sailboat in North Carolina, where it got so cold (minus 17 without wind chill) that the river froze solid for weeks. Even though sailboats have terrible insulation, I kept warm using mostly a Mr. Heater Buddy and an electric heater backup. The electric one wasn’t very reliable and obviously didn’t work when there was no power to connect to. Because the Mr. Heater wouldn’t last all night on high with the small green canister (and I didn’t like keeping propane down below), I connected a 20 pound tank to it from the cockpit using an adapter and long hose. Even though the Buddy burns propane, it’s considered safe for indoor use due to a low oxygen sensor, overheating sensor, and tipover sensor that will shut it down.

CO Sensors

In any case, one of the best ways to help protect yourself or your family from CO poisoning is to use a sensor. Your house may not have a CO sensor in it, and even if it does, it may not be sufficient to tell you the amount of CO in the room you’re sleeping in, especially if you’ve walled off parts of your home to conserve heat.

I’d suggest that you make sure you have a CO sensor in the room you’re heating in an emergency, and if that’s not possible, just buy one. They’re not that expensive. Also, something like this is dangerous enough that due to them being so inexpensive, it doesn’t hurt to have a backup. This one plugs in and has a battery back-up for double protection.

Also, if you’re going to be traveling to someone else’s house, especially something like a cabin or an Airbnb, you should bring along a portable CO sensor. (Here’s a 3-pack of portable sensors that take AA batteries.) In case you didn’t see it in the news recently, actress Anna Faris and her family almost died over Thanksgiving all due to CO poisoning at an Airbnb rental in Lake Tahoe that didn’t have a CO sensor. I’m not sure what the underlying cause of the CO was but a functioning sensor would have helped a lot.

Keep in mind that some combustion heaters that are typically safe indoors may not be in higher altitudes due to the lower amount of oxygen available for combustion, and any externally-vented heater might cause problems if the ventilation is blocked. Also, it’s possible for something running outside to bring in CO if it’s too close to a window. In all these cases, a sensor located in the right place could help mitigate that threat.

By the way, this information goes just as well for camping, staying in a cabin or in some kind of improvised shelter. A portable CO sensor wouldn’t take up too much space or weigh much in your pack but could save your life.


Most people understand the fire risks of using a heater indoors during an emergency or just any cold weather and take necessary precautions. Unfortunately, many people don’t understand the risks of death or serious injury due to carbon monoxide poisoning or how common it is. By using the correct type of heater, you can avoid exposure and poisoning but during an emergency, this isn’t always possible. Taking extra precautions such as assuring proper ventilation and using a carbon monoxide sensor will make things much safer for you and your family.

About Graywolf

Graywolf is a former Counterintelligence Agent and US Army combat veteran. His experience as an agent, soldier and government contractor on assignments around the world gives him a unique perspective on the world and how to deal with it. His website is Graywolf Survival.



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  • Thank you for sharing this! I almost died of CO poisoning in Alaska ages ago. The houses there are extremely airtight, and when a pilot light went out, that was it. The carbon monoxide detector (and my roommate, who was conscious in another part of the house,) saved my life. As a relatively new prepper, the memory of that experience has made me extremely nervous about emergency heat sources. Thank you for the additional clarification! I’m getting a Mr. Buddy.

  • We live in north eastern Utah at an altitude of approximately 5,300 feet. Do you think we would have problems with CO from a Mr. Buddy here? Obviously, we would be using CO detectors.

    • Its time to do some research, Karl. Catalytic heaters rely on super clean consumption of propane. As altitude increases, the percentage of oxygen in the air declines. This leaves less oxygen to combust with propane and create that efficient process.

      Some provide specific altitudes to not exceed when using.

      Its tough to think about cracking a window at 5’F, but without positive air flow, there would be some degree of heightened risk of CO exposure.

  • Some more notes on the Anna Faris near-tragedy

    Anna Faris and family ‘lucky to be alive’ following carbon monoxide incident at Tahoe vacation rental home

    The Fire Protection District said the home had an indoor carbon monoxide level of 55 parts per million, even with windows and doors open for ventilation. The maximum recommended indoor level of carbon monoxide is 9 parts per million.

    Fire Chief Mike Schwartz said. “Situational awareness is so important. Whether you are at home or traveling, it is important ensure that smoke and CO alarms are in working order anywhere you stay. It’s not a bad idea to consider bringing your own alarm when you travel, just to be safe.”

    Suggestion: Use the search phrase CARBON MONOXIDE DETECTOR on Amazon to see a variety of such equipment. Some units are battery powered; some require wall plug-in. Some have an LCD display; some just have a beeper. Choose what makes the most sense for you. Personally, I like the idea of a battery powered LCD display model, so that if house power is lost or you’re traveling or camping, your CO meter is still reliable. A model that works on wall power that has a battery backup would even be better. YMMV.

    In general, the larger the room and the better it is ventilated, the less the CO risk if you’re burning fuel that is CO risky. That’s also why a lot of fuels are specified for outdoor use only, even if that’s widely ignored. Really high risk areas would be small AND poorly ventilated (if at all) spaces like tents, vans or RVs.


  • Most devices with an open flame do not create carbon monoxide but can still lead to oxygen deprivation.

    A Buddy heater is not catalytic.

    Most modern heaters have a temperature sensitive gas valve that turns off the gas if there isn’t enough oxygen to burn hot enough to keep the valve open.

    Very few portable heaters have a system (electronic) to turn off the heater if it is generating CO.

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