Carbon monoxide (CO) is a highly toxic gas that is colorless, odorless, and produced each time a fossil fuel such as gasoline, natural gas, or coal is burned. Fossil fuels contain high levels of carbon, and when they are burned in a process called incomplete combustion, the carbon reacts with oxygen in the air to form carbon monoxide gas.

Many homes have heating and cooling elements, such as a furnace or a water heater, that are powered by fossil fuels, and thus, carbon monoxide gas can be emitted in these homes. Usually, the levels of CO emission remain low enough not to be dangerous with proper ventilation.

When a human comes into contact with too much carbon monoxide gas, otherwise referred to as carbon monoxide poisoning, the symptoms can include the following:

• Nausea or stomach pain
• Blurry vision
• Dizziness
• Headache
• Fainting

Carbon monoxide detectors use sensors to monitor the amount of toxic gas in the air. Carbon monoxide detectors can use different types of technology to identify noxious gas in the air inside of your home. Just like you can buy different styles of detectors, you can buy detectors with different sensors. Here are some of the most widely used sensors.

Electrochemical Sensors

The Cove carbon monoxide detector is an electrochemical sensor. An electrochemical carbon monoxide sensor uses the chemical properties of carbon monoxide to determine the concentration of the gas in the air. Essentially, multiple electrodes inside of the device are submerged in a chemical liquid or gel. These electrodes measure chemical reactions between the air that seeps into the device through a porous membrane and the inside of the device. The chemical reaction creates an electrical output that is directly proportional to the amount of carbon monoxide in the air next to the sensor. Electrochemical sensors are considered the highest quality type of sensor available. They are the best at detecting carbon monoxide levels in the air, making them the best at keeping your home safe. They also have a long lifespan.

Metal Oxide Semiconductor Sensor

Carbon monoxide alarms that use metal oxide semiconductor sensors utilize circuitry to detect gas in the air. When carbon monoxide comes in contact with the circuits inside of the device, the device’s electrical resistance is lowered. This process triggers the alarm that lets you know there is too much lethal gas in your home’s air. These sensors usually come in plug-in form.

Biomimetic Sensor

Using color-changing liquids that change color as they absorb carbon monoxide, this sensor mimics the response of hemoglobin in human blood to carbon monoxide. When the liquid inside of this device comes in contact with carbon monoxide, it changes color. A separate sensor monitors the color change of the liquid and sets off the alarm when the color change is drastic enough. Then, after the alarm has gone off, a biomimetic sensor can be rest by spending time in an environment that is free of carbon monoxide. After it has reset, it is ready to be used once again.

Optochemical Sensor

This sensor uses color to signify the amount of carbon monoxide in the air, much like the biomimetic sensor. A pad inside of the device will change color as it detects the gas in the air. Unlike the other sensors, though, optochemical sensors cannot tell how much carbon monoxide is in the air. Although you should always immediately evacuate an area with raised levels of carbon monoxide in the air, knowing the saturation level of the air allows you to know how deadly it is to take it into your body. All carbon monoxide alarms are designed to sound the alarm before levels get high enough to cause you any harm, but you can never be too safe

If the carbon monoxide detector in your home goes off, gather everyone (including pets) and evacuate immediately. Call 911 and do not re-enter the home until it has been deemed safe by emergency personnel. Being outside in the fresh air is the best possible place to be if you’ve been exposed to CO and are waiting for your home to air out. Remain calm. Go to the hospital and get tested for CO poisoning if needed. (Read more about symptoms of CO poisoning in this article.) Do not wait until you display symptoms of carbon monoxide poisoning before leaving your home. Stay safe and exit at the first sign of a leak.

It depends on the size of your home, how many levels you have, and how many bedrooms. According to the International Association of Fire Chiefs, at minimum, you should have a carbon monoxide detector on every level of your home, including the basement. It is also recommended that a carbon monoxide detector be placed within 10 feet of every bedroom door.

Smart carbon monoxide detectors should be placed in all the same spots that traditional CO detectors go. Regardless of whether or not your state requires you to install carbon monoxide sensors, the United States Consumer Product Safety Commission recommends that every home have a carbon monoxide detector.

Carbon monoxide detectors should be located:

• Every level of your home, including the basement
• Outside of each bedroom
• Near the kitchen
• Near the bathroom
• Every 1,200 square feet
• Far enough away from vents and fans that the heat from these appliances won't case a false alarm
• Far enough away from kitchens and bathrooms to reduce the potential for cooking smoke or bath steam to cause a false alarm
• Away from where the sensor could be affected by drafts, like next to windows
• In a place where it is easy to clean (don’t allow the sensor to collect dust)
• In a place where it won’t get knocked over

If you have any questions about where to place carbon monoxide detectors inside of your own home, contact your local fire prevention officers. They are trained to assist you with all things relating to fire safety and prevention. In order to best place carbon monoxide sensors, people have sought an answer to whether the gas rises or falls in an air-filled room.

Carbon monoxide is lighter than air, but only slightly. Because the weight difference between the two substances is so minimal, carbon monoxide does not settle in a neat area above the air in a room. Instead, its similar weight allows it to intermingle with the air, mixing in with what we normally breathe. It moves through rooms regularly with the flow of air.

Since this deadly gas does not rest above or below the air in a room, it is okay to install a carbon monoxide alarm at practically any height. In fact, you may have noticed as you’ve gone into other homes that two of the most popular placements for these devices are up on the ceiling paired with smoke detectors (placed high up because smoke rises above air) and closer to the ground as a plug-in detector.