Comparing Oxygen Depletion Sensors and Carbon Monoxide Detectors

An oxygen depletion sensor (ODS) can be found in most vent-free fireplaces, vent-free heaters, and propane space heaters. If the level of oxygen in the air becomes too low, these sensors are used to stop the fuel supply.

Comparing Oxygen Depletion Sensors and Carbon Monoxide Detectors

Image Credit: GasLab

The sensors make sense because a lack of oxygen has clearly negative connotations, but it is important to note that a different gas has to take the place of oxygen in the event that the levels become too low. The replacement gas can be carbon dioxide, which is harmful, or carbon monoxide, which can kill.

When customers ask if the safety of gas space heaters is improved through the use of oxygen depletion sensors, the reply is, “It isn’t the lack of oxygen that kills, it is the increase in carbon monoxide.”

Where are Oxygen Depletion Sensors Used?

Oxygen depletion sensors (ODS) are frequently seen on vent-free fireplaces and heaters. The sensor is configured to cut off the fuel if the level of oxygen in the room falls from 21% (normal air) to 18.5% oxygen by volume or less.

All ANSI-certified vent-free units have been required to have an ODS since the 1980s. Gas and vent-free fireplace and heater manufacturers often cite their record of having no recorded deaths related to a lack of oxygen when their heaters were employed.

There is an issue with the logic of this statement because if oxygen levels in a room drop from 21% to 18.5% by volume, then 2.5% of different gas has to replace it.

If that 2.5% of gas is carbon monoxide, it will kill anyone in the room. The inhalation of CO levels more than 1% by volume is fatal in a matter of minutes.

Oxygen depletion sensors may make the user feel safer when they are referred to in heater manuals, but they are not the full solution. For this reason, carbon monoxide detectors are more crucial.

Where are Carbon Monoxide Detectors Used?

Carbon monoxide poisoning (CO) is the second most frequent cause of death as a result of non-medicinal poisoning in the US, and the most prevalent cause of poisoning found internationally.

The CDC explains that more than 10,000 people are poisoned by CO every year, and more than 438 people in the U.S. die each year as a result of CO poisoning. Most US states now demand CO detectors in homes for this reason.

The majority of furnaces and heaters are not supplied with separate CO sensors because CO detectors are comparatively cheap and simple to install. Homeowners are strongly encouraged or legally required in certain states to have a CO detector installed near the furnace of the home and in each bedroom.

A carbon monoxide detector should always be available close by even if an oxygen depletion sensor is used with a heating device.

What About Electric Space Heaters?

This article only focuses on flame heaters that burn propane or gas. As electric heaters do not burn fuel, they do not emit carbon monoxide or consume oxygen. A CO or ODS detector is therefore not required for an electric heater.

Why ODS or CO Detectors Won’t Save You

Regardless of the reliability of heaters with a CO detector or an ODS sensor installed, it would still be unwise for an individual to put their health at risk, or that of their families, for a device or part that costs only a few dollars. The following warnings are included in heater manufacturer’s manuals:

  • An open-flame heater should not be utilized indoors before opening a window.
  • An open-flame heater should not be used while sleeping.

Every manufacturer of furnaces offers this warning:

  • All furnace services should be annually investigated for leaks of carbon monoxide.

Even if a gas heater already has a carbon monoxide detector or an oxygen depletion sensor installed, it is still good advice.

This information has been sourced, reviewed and adapted from materials provided by GasLab.

For more information on this source, please visit GasLab.


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