Why You Need A Carbon Monoxide Detector – Get The Facts

Carbon monoxide detectors are required in all homes in every state, excluding Hawaii and Kansas, under state legislations. Detectors can prevent accidental CO poisoning from common domestic appliances including gas stoves, furnaces, heaters and generators and must be placed on each floor.

Every year 50,000 Americans land in emergency departments due to poisoning by carbon monoxide (CO). The gas is odorless and colorless, and is nearly impossible to identify when it’s at high concentrations. Carbon monoxide monitors are sensitive to the gas and alert you upon detecting high levels.

This article discusses CO and several of its health implications. We explain why you need a CO detector for the “silent killer” and where to place them. We also discuss some of the best CO monitors you can consider buying. 

Carbon Monoxide Signs And Symptoms

Carbon monoxide or CO is a colorless and odorless gas produced due to incomplete combustion when fuel is burned.

Even though you cannot smell, see, or hear CO, you can detect it by common signs like:

  • Health Symptoms: People usually notice CO emissions due to deteriorating health signs. If everyone around the house starts experiencing nausea, headache, shortness of breath, and disorientation simultaneously, you should suspect CO exposure.

In case of CO poisoning during sleep, people often die without showing any related symptoms.

  • Soot Stains: Soot is a black or grey combination of carbon and dirt. Soot stains around the source are a common occurrence in case of incomplete thermal combustion. In cases of CO toxicity, patients can even present with soot in their airways.

It may indicate CO production if you notice dark powdery stains on furniture, clothes, or the ground.

  • Smell Of Exhaust Gases: CO emission is never an isolated incident. Even though you cannot smell CO, the odor of other exhaust gases emitted with it is distinct and can be a clear sign of possible CO leaks.

However, none of these signs or symptoms are scientific or reliable, a dependable indicator like a CO detector is necessary. They are sensitive to CO levels and will immediately alert you in case of excess CO, giving you enough time to vacate your home and contact emergency services.

Carbon Monoxide Detector Requirements

CO poisoning claims at least 430 lives in the USA each year. CO exposure can also lead to irreversible cognitive damage even if a person survives.

Given the life-threatening consequences of CO, and the fact many household appliances produce it (e.g., furnaces, heaters, gas-stoves and ranges) installing CO detectors is crucial.

They have an electric-powered sensor that is sensitive to even slight changes in CO concentrations and rings an alarm in case of dangerous CO levels.

At 50 ppm or less CO, a monitor takes a few hours to set the alarm off. However, at higher levels, the detector will alert within a few minutes.


As of January 2017, 27 states in the USA had mandated the installation of CO detectors in homes under state statutes. Now, every state except Kansas and Hawaii require them. The Carbon Monoxide Safety Act binds everyone that has a heater, fireplace, or attached garage etc to place a CO alarm on each floor of the building.

States that require carbon monoxide detectors in homes (under state statute legislation). Data collected from National Conference Of State Legislatures. Blue indicates the states that require CO detectors in the home. Many of these states also require smoke detectors.
States that require carbon monoxide detectors in homes (under state statute legislation). Data collected from National Conference Of State Legislatures. Image created by Theresa Orr for Plentifulair.com

This means you need to install a carbon monoxide detector on each floor of your home.

Types of carbon monoxide sensors

The efficiency of a CO detector depends on its sensor. There are the four main types of CO sensors you can install in your home:

1. Opto-Chemical: This is a chemical pad. When the chemical reacts with CO, the pad changes color. For example, in the case of potassium disulfitipalladate pads, palladium is released upon reaction with CO, and the bag turns yellow to brown to black, indicating CO exposure.

  • This is the cheapest sensor and offers the least protection against CO poisoning.

2. Biomimetic: This sensor uses metal salts like cyclodextrins and chromophores to detect CO. Hemoglobin contains iron that changes color in the presence of CO. The biomimetic sensor is designed to mimic Hb. It is connected to an infrared light source and alerts you of high CO via LED lights.

  • This is one of the most reliable CO sensors.

3. Electrochemical: It is made of electrodes and sulfuric acid (or other electrolytes). The monitor detects CO when it is oxidized at one of the electrodes.

  • This highly-accurate sensor uses minimal power and lasts around five to ten years.

4. Semiconductor: This CO detector uses a semiconductor tin dioxide mounted on an insulating base, with an electrical circuit connecting the two. The working principle is that oxygen increases the semiconductor’s resistance while carbon monoxide reduces it.


Digital, portable, and wireless CO detectors are available with each of the sensors mentioned above.

Battery-operated and AC-powered CO detectors are easily available. Here’s what you should remember when installing CO monitors, as per the guidelines issued by the Environmental Protection Agency (EPA):

  • When installing a monitor, place it at least five ft. above the floor. This is because CO is slightly lighter than air and is diffuses through the room and easily rises with warm air.
  • Do not place the device next to the fireplace.
  • Each floor should have a separate detector and should be installed near the sleeping area.
  • Test the device and ensure the alarm is loud enough to wake you up.
  • Smoke detectors work differently than CO monitors and cannot replace CO alarms. However, using modern combination devices that include smoke and CO sensors is safe.
  • Refer to the instructions in the user manual to install the alarm correctly.
  • In the case of battery-operated devices, replace the battery at least once a year (a great way to remember is to replace it on a memorable day each year – like a public holiday – then you won’t forget)
  • Make sure that your detector has a functioning power source all the time.

Best Carbon Monoxide Detectors

Here are some of the best CO detectors you can consider investing in for your home:

Google Nest Protect

Overall, the Google Nest Protect is considered one of the best CO detectors available in the market. This 2-in-1 carbon monoxide and smoke detector alerts you immediately when there’s smoke or CO in the home.

It has a split spectrum sensor that detects gas-burning and smoldering and points out its source. Similarly, it senses even slight changes in CO concentrations and marks the point of emission.

Made by Google, this device is with the search engine, and therefore, it can be controlled remotely via internet devices, provided you have a reliable internet connection.

With App Silence, you can easily turn the alarm off using the Nest App.

An added advantage is that this device tests its batteries and notifies you daily at night whether or not the device is working correctly. This ensures you won’t be bombarded with battery indicators and other machine-related notifications throughout the day.

This detector also functions as a night light. When installed on the ceiling, it lights up whenever someone walks underneath it.

Kidde Battery-Operated Carbon Monoxide Alarm

Next up, we have Kidde Battery-Operated Carbon Monoxide Alarm. It has an electrochemical sensor with two alert modes.

With an 85-decibel alarm, you can stay assured of round-the-clock protection. For user convenience, the device comes with two LED lights that show pulsating colors for power and CO detection, respectively. The monitor displays exact levels of CO.

In commitment to protecting against accidental CO poisoning, the device is battery-operated. The high-quality, long-lasting, 3-AA batteries keep the monitor running in case of power failure.

Kidde Battery-Operated Carbon Monoxide Alarm is UL certified and comes with a 10-year warranty, making it worth considering.

First Alert Onelink

First Alert Onelink is a smart carbon monoxide and smoke detector. It is compatible with Alexa and Apple HomeKit, allowing you to conveniently control your device. The photoelectric smoke detector and electrochemical CO sensor ensure high precision to detect smoke and CO.

It features a state-of-the-art Omni directional speaker, which is Alexa-powered. This speaker enables voice features along with the alarm.

The First Alert Onelink’s Home App gives you easy mobile controls. For example, you can get remote notifications, track CO levels, and customize nightlights remotely via simple touch controls on your smartphone.

Onelink is a modern device offering much more than highly precise CO detection. The AirPlay 2 gives you a wireless multiroom audio system on which you can stream music.

Cool features aside, easy installation is another perk of this CO monitor. It is optimized for ceiling placement with an AC adapter. This arrangement ensures not only highly precise CO monitoring but also enhances acoustic quality when streaming music.,

Alert Pro Carbon Monoxide Alarm Detector

The last product on our list is Alert Pro Carbon Monoxide Alarm Detector. It has an 85 decibels alarm bell that immediately alerts you in case of CO exposure. It has a digital LCD display and voice warning, which ensures the utmost safety and an ultimate user experience.

The five-year manufacturer warranty promises long-lasting optimal performance. This battery-powered device is inexpensive yet reliable and remains unaffected by accidental power cuts.

All-in-all, if you are looking for a cheap yet dependable CO monitor, Alert Pro Carbon Monoxide Alarm Detector is your best bet.

Common Sources Of Carbon Monoxide At Home

We know that incomplete combustion produces CO. Understandably, all fuel-burning appliances and fireplaces pose a risk of CO production.

Here are some of the most common domestic sources of CO poisoning at home:

1. Furnaces

Furnaces are a commonly used heating appliance (around 50% of all households have one). Unlike electrical heaters, they use fuel (typically gas) to produce heat.

To understand how a furnace may cause CO poisoning, it is crucial to understand how it works.

  • Furnaces have pre-installed filters that remove contaminants from the original air stream that is drawn into the furnace by the fan.
  • The air is then propelled into a heat exchanger. It is a chamber that burns fuel to produce heat energy, which is used to warm the air. Understandably, this is where combustion takes place.
  • A blower fan then emits the warm air into the room.
  • In conventional furnaces, CO2 and other exhaust gases produced during combustion are emitted directly through the metal flue.
  • In condensing furnaces, the exhaust gases are sent into a secondary heat exchanger that extracts the maximum remaining heat. As a result, the gases cool down and condensate, and the water droplets drain through the pipe. 

A furnace can emit CO in the following situations:

Dirty Filter

A dirty filter is one of the primary causes of CO production from furnaces (and many other appliances). The filter serves to capture airborne dust and debris. However, it has a specific capacity, and if maintenance is not completed regularly, the filter can become saturated and prevent effective filtration processes.

Since the filter is located at the entrance of the furnace, clogging also hampers the airflow. This results in reduced oxygen supply to the heat exchanger, which leads to CO production.

Clogging and Cracks

We know that exhaust fumes are emitted outside through the vent pipe. These fumes can contain small concentrations of CO.

If the flue or drain pipe is clogged due to a build up of dust, it can lead to overheating, resulting in premature furnace cracks. CO leaks through these cracks into the home.

Improperly-sized ductwork can also cause bends in the exchanger.

While undersized ductwork restricts the airflow, a large (oversized) furnace results in short cycling (heating the space in 10 to 15 minutes). The rapid expansion and contraction due to short cycles lead to cracks in the exchanger.

Inadequate Ventilation

In winters, we tend to shut all the windows and keep our doors closed. As a result, over time, the room naturally contains slightly lower concentrations of oxygen, and as we know, this leads to incomplete combustion and CO production.

Incorrect Placement

Even with proper ventilation, and well-maintained filters, it is crucial to place the furnace in an open space, allowing the air to pass through it. Failure to do so causes overheating (hence cracks) and restricts oxygen supply, generating CO.

Plentiful Air has a complete guide to minimize CO production in furnaces available here.

2. Generators

Generators are fuel-burning appliances, and can produce CO. Therefore, it is strictly advised not to operate a generator in a closed room, even with open windows.

This includes basements. Never run a generator in your basement or garage (etc), even if you have doors or windows open – always run the generator outside.

3. Vehicles

Cars and trucks typically have internal combustion engines, which can produce high concentrations of CO. Event the heaters used in vehicles can pose a significant risk of CO emission.

The CO produced as a result is propelled by the exhaust fumes. At homes that have attached garages, CO from vehicles can easily make their way inside.

Obviously this doesn’t apply to electric vehicles that operate via a charged battery.

4. Stoves

Wood stoves and gas ovens (or ranges) are other major sources of CO poisoning. Even when a gas stove is properly adjusted and serviced, CO levels range from 5 to 15 ppm. In contrast, near poorly adjusted gas stoves, CO can be higher than 30 ppm.

Other Ways To Prevent Carbon Monoxide Poisoning

The following steps can help prevent CO poisoning:

  • Never run gasoline-powered appliances in enclosed rooms like basements or garages.
  • Always ensure adequate ventilation. Keep as many windows and doors as possible.
  • When the bathroom is in use for long, ensure to use a bathroom fan.
  • If you have a garage attached to your house, don’t run a vehicle inside it.
  • Avoid using gas ovens.
  • Get heating and cooking appliances regularly checked and serviced. Also clean them and take care of required maintenance.
  • In case you use wood stoves, ensure that they are certified to meet EPA emission standards.
  • Do not use heaters or furnaces while sleeping because any health-related signs of CO poisoning may go unnoticed if a person is sleeping.

Carbon Monoxide Toxicity

Oxygen is essential for us to survive. This is because our body uses inhaled oxygen to produce the energy required to carry out vital processes (i.e., life).

The oxygen is supplied throughout the body while bound to a red blood cell protein called hemoglobin (Hb). Hb takes oxygen from the lungs and transports it to all the tissues and organs.

Unfortunately, Hb has a 250 times higher affinity for CO than oxygen. This means Hb prefers to bond with the CO over oxygen, even if oxygen levels in the environment are sufficient. So, even though CO is not poisonous, in situations of high CO concentrations in the air our body quickly becomes depleted of oxygen.

This results in severe energy deprivation and eventual damage to the brain, heart, and other organs.

At high concentrations, CO exposure can prove fatal within 5 minutes making detectors a necessity

Side Effects

Common side effects of CO are:

  • Nausea, fatigue, and headache
  • Respiratory distress
  • Disorientation
  • Hallucinations
  • Anorexic brain injury (irreversible death of brain cells due to severed oxygen supply)
  • Ischemia (reduced blood supply to the heart)
  • Heart failure
  • Memory loss

Risk Factors

The following people are highly susceptible to CO poisoning:

  • Children: Children’s lungs are not fully developed. Therefore, factors like CO can trigger extreme respiratory distress.
  • Elderly: In old age, many people develop chronic diseases and cardiovascular and respiratory disorders. Hence, exposure to even small concentrations of CO can severely affect their health.
  • Factory Workers: CO is one of the most dangerous industrial hazards. Factory workers are often around high-end fuel-burning machines. Unfavorable circumstances may lead to incomplete combustion and CO emission.

Every year, thousands of American workers die due to CO poisoning.

  • Immunocompromised Individuals: People having pre-existing immune diseases, or chronic diseases are comparatively more prone to CO poisoning.

Safe And Dangerous Levels

As per the Occupational Safety and Health Administration (OSHA), 50 ppm of CO is safe. However, at 70 ppm, initial symptoms of CO poisoning (nausea, headache, and chest tightening) start showing.

Exposure to beyond 150 to 200 ppm of CO can prove fatal.

According to the Environmental Protection Agency (EPA), the average CO concentration in homes without gas stoves is 0.5 to 5 ppm (those with stoves can reach 30 ppm or higher).

What To Do In Case Of Carbon Monoxide Poisoning

In case of CO exposure, immediately vacate the house, call emergency services, and rush to the hospital. Your health provider will give you an oxygen mask to breathe through. This restores the oxygen supply to the body.

A blood test is done to confirm CO poisoning.

Afterward, they will decide on an appropriate treatment method based on the length of exposure, CO levels, and your general health.

In healthy individuals, promptly fixing the severed oxygen supply is sufficient. However, in people who experience severe symptoms like brain injury or heart failure, further treatment is required. 

Frequently Asked Questions

How Is Carbon Monoxide Produced?

There are four situations that can lead to CO production from incomplete combustion. These are low oxygen, incorrect fuel metering, inadequate time (for combustion) and low temperatures.

1. Low Oxygen: All heating processes require oxygen. Especially during thermal combustion (like have a fire burning in your fireplace, or cooking food on your gas stove), you need excess oxygen to ensure the complete oxygenation of carbon and other exhaust gases produced by burning fuel.

  • If there isn’t enough oxygen, the carbon understandably undergoes incomplete combustion, i.e., it is not properly oxygenated, which results in CO production.

2. Incorrect Fuel Metering: To achieve perfect combustion, mixing the air (oxygen) and fuel in exactly the required proportions is essential. The ideal fuel and air mixture is 14.7:1 by mass, respectively, and the process of mixing the two components is termed fuel metering.

  • Over fueling can lead to CO emission.

3. Inadequate Residence Time: Residence time relates to how long something remains inside a combustion or heating chamber, i.e., how long something burns for. An inadequate or low residence time is a potent cause of incomplete combustion. The longer something can combust or burn for the better.

4. Low Temperature: Temperature is directly proportional to the rate of combustion. The ideal temperature (equal to or higher than the ignition temperature) for proper combustion depends on the fuel type. For example, gasoline requires at least 495°F (ignition temperature) for self-sustaining combustion.

  • In case of low temperatures, CO will naturally be produced. For example furnaces set on high temperatures will naturally produce less CO than one set to a low temperature.

On the science side of things – Thermal combustion is an heat producing reaction (exothermic) that generates carbon dioxide (CO2), which is one carbon atom bonded to two oxygen atoms. In adverse situations, if carbon only bonds with one oxygen atom (i.e., is not oxygenated completely) carbon monoxide (CO) is produced.

Can You Get Carbon Monoxide Poisoning In An All Electric House?

Carbon monoxide is only produced by heating devices. In an all-electric house, it is not possible to get carbon monoxide poisoning (except if the house has an attached garage that contains fuel-powered vehicles).

What Are The Signs Of Carbon Monoxide In A Home?

Soot stains, the smell of exhaust fumes, and simultaneous occurrence of CO poisoning symptoms (nausea, headache, and shortness of breath) are critical indicators of carbon monoxide exposure. In homes with CO detectors, the alarm is set off, indicating high CO levels.

Is It Better To Have Separate Smoke And Carbon Monoxide Detectors?

Smoke detectors are not super sensitive to CO levels, and therefore, it is crucial to install both smoke and CO detectors at home. However, it is safe to use 2-in-1 combo devices that act as smoke and CO monitors.

Using separate detectors can allow you to place each one more strategically based on the risks, for example CO monitors should be placed near sleeping locations.

Russell Singleton

Russell holds a Bachelor of Science (Environmental and Marine Geoscience) with Class I Honors. He is currently completing his doctorate in science and is passionate about all earth processes, especially isotope geochemistry and paleohydrology.

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