Monitoring Home Air: Important Guide to Carbon Monoxide Detectors

Authored by Dr. Jeff Bennert

Carbon monoxide (CO) is a gas that has no color or smell, and that is deadly to both humans and animals. It is produced by the burning of fuels and can become problematic in areas that are closed off and have poor ventilation. Cars, grills, fireplaces, gas ranges, stoves, and furnaces are all sources of CO emissions.

Because there are no indicators that warn of its presence, the risk of death is high, particularly for individuals who are considered high risk. People who fall in this category include infants, the elderly, people with chronic heart disease, and individuals who suffer from problems with breathing. Although some people are at a higher risk, all people must be cautious as, according to the CDC, there are over 400 deaths annually that can be attributed to CO poisoning that happens unintentionally in the US.

Yearly, as many as 20,000 people are treated in emergency rooms for CO poisoning as well. People can prevent CO poisoning and potential death by taking preventative measures and installing a carbon monoxide detector that meets standards set by Underwriters Laboratory (UL) . These detectors are an important addition to preventative safety measures that must be taken in order to stop CO poisoning from occurring in the first place.

A carbon monoxide detector is not an air purifier or an air ionizer, and will not remove CO from the air. It is a detector only and will not remove pollution or nullify odors the way that an air ionizer or an air purifier will. To best protect oneself and family it is important to learn as much as possible about CO detectors for the home.

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How Carbon Monoxide Detectors Work

Carbon monoxide detectors work by sensing the amount of CO in the air and sounding an alarm when that amount reaches a level that is harmful. Sensors are built into the detector for this purpose; there are several types of sensors which measure carbon monoxide in different ways. The common sensors for CO detectors include biomimetic, metal oxide semiconductor, and electrochemical sensors. When using a device with a biomimetic sensor, dangerous levels of carbon monoxide cause a color change to occur in the sensor’s gel. This color change represents a danger level for humans. When this change happens it causes the alarm to sound. Devices that have electrochemical sensors contain electrodes that are situated in a chemical solution. Carbon monoxide causes the electrical currents to change and, as a result, the alarm sounds. The metal oxide semiconductor is a sensor that is commonly found in plug-in detectors due to the amount of electricity that is necessary for it to function properly. This sensor triggers the alarm when CO touches its circuitry.

Laws Regarding Carbon Monoxide

Carbon Monoxide laws vary across the nation. Not all states currently have them. Some states require detectors in residential buildings only. Some of the states require them in all homes, old and new, while other states only require them in new homes built after a certain date. There are also laws requiring carbon monoxide detectors in schools, daycares, or other childcare centers.

Installation and Where They Should Installed

It is important to follow manufacturer instructions when installing CO alarms in one’s home. Installation recommendations involve placing a detector in the hallways outside each of the sleeping areas. Long hallways should have a device at each end. Every floor in the home should also have a detector, including the basements. When placing the detectors, the ideal location is high toward the ceiling. They should not be placed in areas such as the kitchen, or within five feet of heating vents or appliances that are fuel-burning.


An important part of maintaining one’s carbon monoxide detector involves testing it regularly to ensure that it is in good working condition. Each manufacturer will have instructions that are specific to their brand; most involve pressing some form of test button. Recommendations regarding the frequency with which to test these alarms are also provided by the manufacturer. Once again, there is a rule of thumb to follow in the event that manufacturer recommendations are not readily available. Typically, a detector should be tested once a month. Changing the battery is also another aspect of maintaining CO detectors. Backup batteries should be replaced at least every six months. A simple way to remember this task is to change it when daylight savings time begins and again when it ends. Dust and debris must not be allowed to build up on the device. CO detectors aren’t made to last forever. Most detectors will last between five or seven years before replacement is necessary.

What to do if Carbon Monoxide is Detected

Knowing what to do when the alarm sounds is just as important as having the alarm. Everyone in the home must move quickly and exit the building. Because carbon monoxide has no smell or color, a person should not attempt to locate the source of the leak. Once the premises have been vacated, confirm that everyone is out of the building, call emergency services or 911, ask if anyone is having a headache, nausea, dizziness, or any other feelings of illness. No one should reenter the home for any reason until it has been approved by the fire department or the emergency responders. Often the source of a carbon monoxide is an appliance. If this is the case it should be serviced by a technician that is qualified to inspect and repair it.

Additional Resources

  • Carbon Monoxide Detector Requirements, Laws and Regulations: Read about laws pertaining to carbon monoxide detectors on this page by the National Conference of State Legislatures. Included is a summary of various state laws, as well as a link to a HUD fact sheet page.
  • CDC Guide to preventing Carbon Monoxide: Here the CDC provides a checklist (also in printable PDF form) on how to prevent Carbon Monoxide Exposure and provides a list of FAQs.
  • Carbon Monoxide (CO): This page on the EPA's website talks about the sources and health effects of carbon monoxide in the home.
  • Carbon Monoxide Poisoning: This page from Medline Plus lists the symptoms of carbon monoxide poisoning.
  • Carbon Monoxide Alarms: The Bloomington Fire Department offers information about carbon monoxide poisoning on their web page. Symptoms and sources of CO poisoning, prevention and CO alarms are some of the subjects that they cover.
  • Carbon Monoxide Poisoning: Dangers, Detection, Response, and Poisoning: The nature of carbon monoxide, sources, the threat that it represents, and how alarms detect carbon monoxide, are some of the points that this page discusses.
  • Carbon Monoxide Indoors: Go here for a page about carbon monoxide poisoning by the American Lung Association. The information they provide includes the carbon monoxide detectors, the health effects of CO poisoning, and how to prevent it from occurring.
  • Carbon Monoxide Poisoning - Prevention: Avoiding carbon monoxide poisoning is the topic of this page on the Mayo Clinic website. CO detectors, maintaining proper ventilation, and proper usage of carbon monoxide-emitting appliances are some of the topics discussed here.
  • Preventing Carbon Monoxide Poisoning (PDF): The dangers, health effects, and sources of carbon monoxide are provided on the page that is associated with this link. By clicking on the link, readers are opening a PDF that also explains how to prevent CO poisoning and using carbon monoxide detectors.
  • Carbon Monoxide Poisoning and Detectors: Click this link for facts and figures regarding carbon monoxide. The page also gives its readers plenty of information about poisoning and detectors.