Molecular Monday: Carbon Monoxide vs. Carbon Dioxide

Today’s post is part of a special series here on Planet Pailly called Molecular Mondays. Every other Monday, we take a closer look at the atoms and molecules that are the building blocks of our universe, both in reality and in science fiction. Today’s molecule—or rather, today’s molecules—are:


As I’ve mentioned before, I’m not the best at chemistry. So when someone told me carbon monoxide and carbon dioxide are basically the same thing, I felt pretty sure this was wrong. But not 100% sure. So I did some research.

On the surface, carbon monoxide (CO) and carbon dioxide (CO2) do seem kind of similar. They’re both colorless, tasteless, odorless gases. They’re both produced by combustion. And they’re both deadly to humans.

A common conversation between CO2 (on the left) and CO (on the right).
A common conversation between CO2 (on the left) and CO (on the right).

Death by Carbon Dioxide

If you breathe in too much CO2, you’re probably not getting all the oxygen you need. In most cases, this will make you feel a little uncomfortable, and you’ll probably experience an uncontrollable urge to step outside for some fresh air.

It takes a lot of CO2 to kill a human, so unless you’re knocked out or otherwise incapacitated (inhaling large quantities of CO2 could cause you to faint), you’ll probably be okay.

Carbon monoxide, on the other hand, is a more aggressive killer.

Death by Carbon Monoxide

Carbon monoxide loves bonding with the hemoglobin in your blood. It sort of has a fetish for anything that contains iron or similar metals. So inhaling CO reduces your total oxygen intake AND reduces your blood’s capacity to transport whatever oxygen you do get.

This double whammy means it takes a lot less CO to incapacitate and kill a human. Even if you do survive, CO is reluctant to leave your bloodstream once it’s bonded with hemoglobin. So your blood could have diminished oxygen-carrying capacity for a long, long time after exposure.

Similar but Different

So are carbon monoxide and carbon dioxide basically the same thing? In some ways, yes. But if you’re human (or any other respirating animal), there is at least one crucial difference.


Carbon Monoxide from Molecule of the Month.

Why Does Pure CO2 Kill You? from The Naked Scientists.

Inert Gas Asphyxiation from Wikipedia.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.