When to Replace a Carbon Monoxide Detector

Replace carbon monoxide detectors

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Check your CO detector

Check the back of your detector for either a build date or an expiration date. If there's no date or it's more than seven years old, replace it now.

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Close-up of CO label

This label shows a manufacture date.

If you wonder if your carbon monoxide detectors are worn out, they probably are. CO detectors only have a five to seven-year life. Listing a build date or an expiration date on the label is a fairly new phenomenon. If there's no date on yours and you can't remember when you bought it, you're probably due for a new one.

Here are two key things to look for when you buy replacements. First, pick a detector with a “fuel-cell electrochemical” sensor. This type is far more sensitive to CO and less prone to false alarms than models from just 10 years ago. There are other types of sensors on the market (metal oxide and gel cell) that offer longer life. But humidity and temperature changes can reduce their accuracy. When it comes to detecting carbon monoxide, we recommend accuracy over detector life span. Second, experts recommend choosing a model with a digital readout and a “peak level” memory retention feature. That's helpful to emergency personnel if they suspect CO poisoning. If you have small children, consider buying a talking CO detector. A voice warning is more effective than a horn at waking children.

Since carbon monoxide is roughly the same weight as air, it neither rises toward the ceiling nor sinks to the floor. So detectors that don't have a digital display can be mounted anywhere as long as they're at least 15 in. below ceilings.

Just make sure you install one on each level of your home. Locate them in hallways near bedrooms but at least 15 ft. away from fuel-burning appliances.

Photo 1: Combustible gas/CO detector

Photo 2: Digital display detector

Photo 3: Wall-mount detector

Three Types of CO Detectors

Install a combination combustible gas/CO detector in areas heated by natural gas space heaters (Photo 1).

Locate digital-display wall-mounted detectors at eye level so you can monitor the CO levels (Photo 2).

Install wall-mounted detectors anywhere on the wall, but at least 15 in. below the ceiling (Photo 3).