A carbon monoxide detector alerts you to the presence of the chemical CO in your home so you can quickly exit the house and then request help.
CO is a deadly gas that can kill. What makes it more dangerous is that it is colorless, has no odor and therefore can’t be detected by humans on our own. It’s a very serious problem if you have a CO leak in your home and only having a carbon monoxide detector(s) in your home will quickly alert you to the problem.
But even serious subjects often have a lighter side. One of the things people often wonder is if gases other than CO will trigger a carbon monoxide detector? To wit…
Can a fart set off a carbon monoxide detector due to the presence of gas? It’s a funny question but flatulence typically contains a number of common gases including methane, nitrogen, oxygen, hydrogen, carbon dioxide and even hydrogen sulfide.
A CO detector is only designed to detect carbon monoxide but some models are less able to resist certain chemicals such as nitrogen, methane, carbon dioxide and oxygen which are found in human flatulence and could possibly trigger a false alarm.
CO detectors are often tested for resistance against certain levels of chemicals so while unlikely that flatulence would set off a CO detector on its own, it could happen with some models.
There are other reasons why a CO detector is susceptible to false alarms as we’ll see below. Let’s take a closer look at how CO detectors work and what they actually do monitor and respond to.
Will flatulence trigger a carbon monoxide alarm?
Flatulence does not contain carbon monoxide but does contain methane. While an excessively high methane concentration may accidentally set off a CO detector it would have to be very high and very concentrated. Some detectors specify right in the instruction manual that they have been tested to resist certain levels of specific chemicals to avoid false alarms and methane is typically one such chemical.
Having said that, flatulence is typically comprised of the following gases in order of prevalence: Nitrogen, hydrogen, carbon dioxide, methane and oxygen. Since CO detectors aren’t specifically designed to detect any of these gases, one would expect that the alarm shouldn’t get triggered.
It’s worth taking a closer look at what a CO detector will detect because you shouldn’t get a false sense of security and believe you are protected when you’re not.
As we’ll see below, CO and smoke detectors can accidentally trigger when certain gases, chemicals or events occur in high concentrations. CO detectors can also malfunction at times too.
What does a carbon monoxide detector actually detect?
A carbon monoxide detector is designed to alert homeowners to elevated levels of carbon monoxide (CO) which is a potentially deadly gas that is both odorless and invisible. In other words, you can’t smell it or see it but it can kill you if it builds up within your home to a large enough degree.
Depending on the model, your carbon monoxide detector may only be able to detect the presence of CO when it reaches a certain level such as 30 ppm (parts per million).
A carbon monoxide detector will not alert you to the presence of a gas leak in a home nor will it detect smoke, fire or an elevated temperature that could also indicate a fire.
You can purchase combination smoke/CO detectors that alert you to both the potential of a fire or carbon monoxide threat but a CO detector on its own is designed to detect carbon monoxide only.
What other gases can set off a carbon monoxide detector?
CO detectors are designed to detect carbon monoxide and only that. It’s important to note that CO detectors detect the presence of carbon monoxide and not the smell from a gas or chemical.
Right in the instruction manuals of various models, you will often see text that describes what their CO detector can and can’t do. Examples include:
- It is NOT designed to detect smoke, fire or any other gases. (Kidde)
- This carbon monoxide alarm will not sense smoke, fire, or any poisonous gas other than carbon monoxide even though carbon monoxide can be generated by fire. (Kidde)
- CO alarms should not be used to detect the presence of natural gas (methane), propane, butane, or other combustible fuels. (Home Depot)
- This CO Alarm is designed to detect carbon monoxide from ANY source of combustion. It is NOT designed to detect smoke, fire, or any other gas. (First Alert)
- The following substances can affect the sensor and may cause false actions: methane, propane, isobutane, isopropanol, ethylene, benzene, toluene, ethyl acetate, hydrogen sulfide, sulfur dioxides, alcohol-based products, paints, thinner, solvents, adhesives, hair sprays, aftershaves, perfumes, and some cleaning agents. (SITERWELL)
CO detector manuals typically also contain a number of other provisos and caveats to ensure they are used correctly and not misunderstood.
CO detectors don’t replace a fire/smoke detector nor should they be used to detect gas leaks because that is not what they are designed for.
What chemicals can impact a carbon monoxide detector?
Research has shown that CO detectors can be triggered if they are exposed to certain concentrations of the following chemicals:
- Cetylen
- Dimethyl sulfide
- Ethyl alcohol
- Ethylene
- Hydrogen cyanide
- Hydrogen sulfide
- Isopropyl alcohol
- Mercaptan
- Methyl alcohol
- Propane
- Nitrogen dioxide
- Sulfur dioxide
It’s important to note that you are not actually protected against these chemicals by using a CO detector. These are chemicals that have been known to interfere with a CO detector. Source: Fire Engineering
FYI: One chemical on the above-mentioned list is Mercaptan which is often added to a home’s natural gas supply and smells like rotten eggs, to alert home owners that they have a gas leak.
Since CO alarms are susceptible to other chemicals, manufacturers may take care to try to minimize this occurring. CO detectors are often tested against certain chemical threshold levels to try to minimize the chance that they cause a false alarm.
Let’s take a closer look at what this means.
What chemical thresholds can typical CO detectors resist?
Some CO detectors can be falsely set off due to various events, which we’ll discuss below. They can also be set off by some chemicals if they are found in a very high concentration. Some online research shows that various models of CO detectors can resist being set off by other chemicals when they are below the following concentrations:
| Chemical | Resistance level in parts per million (ppm) |
| Methane | 500 ppm |
| Butane | 300 ppm |
| Heptane | 500 ppm |
| Ethyl Acetate | 200 ppm |
| Isopropyl Alcohol | 200 ppm |
| Carbon Dioxide | 5000 ppm |
If these numbers are accurate for your particular CO model, it means that your alarm should not trigger if it detects these chemicals because the reading is under the stated figures shown in the table above.
We see from the above list that the resistance level of methane is quite high and is the only gas on this list also found in flatulence. The other gases in flatulence aren’t even targeted.
Add that to the fact that CO detectors are only designed to react to carbon monoxide and we can conclude that the chance of setting off a detector due to flatulence is at best fairly low.
What can falsely set off a CO detector in your home?
There are a number of things that can lead to a carbon monoxide detector falsely being set off within your home, some of which you may not even be aware of.
They include:
Excessive levels of steam from a bathroom or shower
High levels of steam can cause a CO detector or smoke detector to trigger.
Solution: Don’t install a CO detector directly outside a bathroom if possible. Ventilate the room (open a window, run the ceiling fan) when showering especially if you’re producing significant steam.
You can also close the bathroom door when showering to keep the steam within the bathroom with the window open.
Some smoke detectors – particularly photoelectric models – can also trigger for a few seconds or longer when concentrated steam from a shower hits its sensors.
Using an outdated CO detector that is past its expiry date
CO detectors have fine sensors and other parts that can wear out and become less reliable over time.
Solution: A CO detector should be replaced at or before its expiry date, a date that will be stamped or otherwise be easily visible on the unit itself. A CO detector is usually good for 5-7 years although some models can last as long as 10 years.
When a CO detector has reached its end of life, it will often alert you in a specific way so it’s important to understand how your model responds. A CO detector will often beep 4 times and then pause (before repeating) when it is alerting you to the presence of carbon monoxide.
But it may also beep 1 time, pause, beep 1 time, pause and continue doing this to let you know the detector has now expired and should be replaced.
Do not mistake the beeping. You should always assume that when your CO detector beeps, that you have a carbon monoxide leak and put your safety first. But you should also be aware of how your detector acts in certain instances.
Leak from a neighboring residence
It is possible that if you live in an apartment, semi-detached home or other communal living space, a carbon monoxide leak from a nearby unit could trigger your CO detector.
Solution: Either way, it’s a danger to you if it sets off your alarm and you need to get out of the house and alert your neighbor(s) too in a safe way.
Sources outside your house
Traffic fumes from a car or from other vehicles in a heavy commercial area or construction zone may incorrectly set off a CO detector if your windows or doors are open. Grilling or barbequing too close to the home or in your garage (definitely not recommended) can also cause CO fumes to set off an alarm.
Solution: Close your windows when appropriate and never place a gas or other grill or barbeque in a closed area like a garage.
Air and ventilation issues
A home that is too tightly closed and doesn’t allow airflow from outside the house can cause gases inside the house to accumulate. Conversely, a home that has air leaks in the ductwork or venting can introduce carbon monoxide into the home if fuel-burning appliances are involved i.e. gas furnace, water heater, fireplace, wood-burning stove, etc.
Solution: Air your house out from time to time by cracking a window(s) when appropriate. If you suspect an air duct or other leak, quickly act on it to get it checked out by a qualified professional only.
Summary
CO detectors are designed to only detect excessive levels of carbon monoxide and not any other chemical. They are also generally tested to ensure that they resist being set off by other chemicals they may encounter in the home. In that regard, it’s highly unlikely that a carbon monoxide detector would be set off by flatulence.
Having said that, there is no guarantee that every brand and model of CO detector is of equal quality and the older an alarm is, the more likely it can be susceptible to a false alarm.
Never ignore the alarm on your CO detector triggering and don’t ever assume it’s a false alarm.
It’s always better to assume that your CO detector triggering is a real event than to ignore it and assume it’s a false alarm. If your carbon monoxide detector is triggered, get to fresh air (leave the house) and call your gas company or authorities for help.
Common signs of carbon monoxide poisoning include the following:
- Nausea/vomiting
- Stomach pains
- Breathing difficulties
- Tiredness
- Confusion
- Suddenly collapsing
Click here if you’d like to learn more about exactly how CO detectors alert you to the presence of elevated carbon monoxide.
We also discuss how you can suffer carbon monoxide poisoning from a propane heater.