In this blog, we take a look at a concerning issue: people getting carbon dioxide and carbon monoxide mixed up. Find out more about the critical differences, or visit our dedicated range of carbon dioxide and carbon monoxide detectors.

A couple of years ago we posted a blog about the American Red Cross getting confused between carbon dioxide (CO2) and carbon monoxide (CO) in a household initiative. A few years on, we’d like to say that people have stopped getting their gases mixed up, but unfortunately, this is not the case.

We have seen a lot of stories about charities, the media and other organisations not seeming to know the difference. A newspaper in Delaware reported on the death of a woman and attributed it to both CO and CO2. In Melbourne, Australia, a plumbing company offered carbon dioxide testing following the death of a family killed by a carbon monoxide leak.

It’s great that people are raising awareness of gas leaks, but the mix-up is still a concern. Even a Google search for “carbon dioxide” brings up more carbon monoxide awareness websites than we would like to see.


Both of these gases have a lot of similarities – both CO2 and CO are odourless and tasteless. Elevated levels of both gases can cause health problems and even death.

The critical chemical difference is that CO2 contains one atom of carbon and two atoms of oxygen, whilst CO has one carbon and one oxygen atom.

Carbon dioxide is non-flammable, whilst carbon monoxide is flamable – we certainly wouldn’t encourage you to light a match in order to determine which gas is which.

Carbon dioxide naturally occurs in the atmosphere at about 400 parts per million – humans and animals breathe in oxygen and exhale carbon dioxide – we can tolerate a small amount of it. However, carbon monoxide does not occur naturally in the atmosphere and can cause health problems even in low concentrations.

The density of both gases is also different. Carbon dioxide that leaks from a gas cylinder is denser than air and gas detectors should be put nearer the ground, whereas carbon monoxide has a similar density to air and detectors should be placed higher up.


We are often asked if a carbon monoxide detector will measure carbon dioxide levels, and vice versa. Unfortunately, the answer is NO. Carbon dioxide detectors use infrared sensors to detect levels of gas in the atmosphere, whereas carbon monoxide detectors primarily use electrochemical sensors as well as gel sensors and metal oxide semiconductors.

Analox has a wide range of both carbon dioxide and carbon monoxide detectors to suit your requirements, and if you’re still unsure which gas you need to measure, our sales team will be more than happy to advise you.