Carbon monoxide (CO) is an invisible, odorless, tasteless gas produced when fuels don’t burn completely, or are exposed to heat (usually fire).
These fuels include: wood, coal, charcoal, oil, natural gas, gasoline, kerosene, and propane. Because carbon monoxide poses a serious public health risk, most states in the U.S. have made carbon monoxide alarms mandatory in homes.
There’s a myth that carbon monoxide alarms should be installed lower on the wall because carbon monoxide is heavier than air. In fact, carbon monoxide is slightly lighter than air and diffuses evenly throughout the room.
According to the carbon monoxide guidelines of the National Fire Protection Association (NFPA 720, 2005 edition), all carbon monoxide alarms “shall be centrally located outside of each separate sleeping area in the immediate vicinity of the bedrooms,” and each alarm “shall be located on the wall, ceiling or other location as specified in the installation instructions that accompany the unit.”
Specific requirements for smoke and/or carbon monoxide alarms vary from country to country and from region to region. Installation should always be done according to local regulations and other applicable codes.
For US users, learn more about your state's carbon monoxide laws with Carbon Monoxide Detector Installation Statutes.
For UK users, some helpful resources for installation requirements are provided below. Consult your local building codes and fire authorities to determine requirements that may apply in your location.
- England: firesafe.org.uk
- Scotland: firescotland.gov.uk
- Wales: southwales-fire.gov.uk
- Northern Ireland: nifrs.org
Standalone carbon monoxide alarms are often placed low on the wall because they need to be plugged into an outlet that’s near the floor. CO alarms can also have a screen that shows the CO level and needs to be at a height where it’s easy to read.
Do not install carbon monoxide detectors directly above or beside fuel-burning appliances, as appliances may emit a small amount of carbon monoxide upon start-up. A carbon monoxide detector should not be placed within 15 feet of heating or cooking appliances or in or near very humid areas, such as bathrooms.
For more information about carbon monoxide safety, go to National Fire Protection Association.
Proper airflow through the home helps to lower levels of carbon monoxide. "Air-tight" homes with added insulation, sealed windows, and other weatherproofing can "trap" carbon monoxide inside. Electrical appliances typically do not produce carbon monoxide.
According to the National Fire Protection Association (NFPA), several common appliances are often sources of carbon monoxide, including oil or gas burning furnaces, gas ovens, wood-burning fireplaces, and charcoal grills. Carbon monoxide levels can rise quickly if any of these appliances are not properly maintained, are improperly ventilated, or malfunction.
To learn more about carbon monoxide, go to NFPA.
Your Nest Protect sounds an alarm and sends a message to the Nest app or Google Home app when it detects that carbon monoxide (CO) levels have reached an emergency level. It’s important that you always respond to a CO emergency by evacuating the house and calling emergency services.
When the alarm sounds, move to fresh air even if the CO level shown in the app seems low. CO levels may continue to rise rapidly after the alarm is triggered, so the level shown in the app may not reflect the current level of CO in your home.
What to do if carbon monoxide is detected in your home.
The danger of carbon monoxide (CO) depends on a number of variables like the amount of CO in the air, how long you were exposed to that level, and your health and level of activity. CO poisoning can result from being around high levels of CO for a short amount of time, or lower levels of CO for a longer amount of time.
Tip: After the event, your Nest Protect reports the highest level of CO that it detected. This is the peak CO level. You can also find the peak CO level in Protect History. This information can be used by a fire safety professional, or an experienced technician, to help identify the source of the CO.
Important: The symptoms related to carbon monoxide (CO) poisoning can be misdiagnosed, as they are similar to flu symptoms. If your alarm sounds, react accordingly even if you don’t notice the effects.
According to the U.S. National Fire Protection Association (NFPA), the following symptoms are related to carbon monoxide poisoning:
- Mild Exposure: Slight headache, nausea, vomiting, fatigue. These are often described as 'flu-like' symptoms.
- Medium Exposure: Severe throbbing headache, drowsiness, confusion, fast heart rate.
- Extreme Exposure: Unconsciousness, convulsions, cardiorespiratory failure, death.
All members of the household should be familiar with these symptoms. Many cases of reported carbon monoxide poisoning indicate that while victims are aware they are not well, they become so disoriented they are unable to save themselves by either exiting the building or calling for assistance.
According to the Center for Disease Control, certain groups, such as pets, children, and people with chronic heart disease, anemia, or respiratory problems, are more susceptible to its effects.
Nest Protect isn't a low-level carbon monoxide monitor so it alerts you to carbon monoxide only in a Heads Up or Emergency Alarm event.
Individuals with certain medical problems should consider using detection devices with lower Carboxyhemoglobin (COHb) alarm capabilities and warning devices which provide audible and visual signals for carbon monoxide concentrations under 30 ppm.
For more information about alarm thresholds under American National Standard ANSI/UL 2034, refer to the carbon monoxide (CO) precautions section in your Nest Protect User’s Guide. Download your Nest Protect User’s Guide.
For further information, please consult a qualified medical professional or go to the World Health Organization’s document on pollutants.