why does asphyxiation from carbon dioxide cause pain, but other gases such as nitrogen don’t?


Why does nitrogen cause you to just pass out but carbon dioxide causes you to suffocated and feel it? Is it because of the oxygen in carbon dioxide?

In: 42

Your body produces carbon dioxide as a byproduct of your metabolism, so it’s fine-tuned to recognizing elevated levels of that. In contrast, your body doesn’t really have a measure for how much oxygen you’re getting.

So, it’s not the lack of oxygen that makes you feel like you’re suffocating, but the build-up of carbon dioxide. If you start breathing pure nitrogen instead, you’re still getting rid of the carbon dioxide normally, but you’re not getting any oxygen.

The answer is going ultimately be a restatement of the question: high levels of carbon dioxide cause discomfort or pain because our bodies have mechanisms for detecting it, whereas we don’t have comparable mechanisms for detecting low levels of oxygen. (High levels of nitrogen *are* toxic, but only under conditions that never existed until the late 19th century and the advent of pressurized caissons and, eventually, saturation diving.)

The best further elaboration is that situations with elevated carbon dioxide levels *do* happen in nature, and it’s a good idea to get out of them. But low-oxygen conditions are rare in the environment where humans evolved.

Asphyxia – a condition caused by lack of oxygen causing death.

It isn’t necessarily the carbon dioxide that causes asphyxia however it does result in harm and can be potentially fatal to the body.
The body reacts to excess carbon dioxide much more readily than other gases as it is naturally occurring within the body in harmful quantities. The way the body reacts is by breathing (ventilating) more to get rid of it. This gives an
uncomfortable and breathless experience.
The relationship between amount of Carbon dioxide in the lungs and the amount the body needs to breath is illustrated with this graph:

As a side note others have noted that the body does not react to low oxygen levels, this is incorrect. The body has mechanisms that ultimately result in an increased amount of breathing (ventilation) which is quite well illustrated with this graph:

The likely reason for the misunderstanding is that most people don’t get to the point where they experience low levels of carbon dioxide before they experience low oxygen.


When CO2 is dissolved in your blood, it makes carbonic acid. Our bodies can detect the levels of carbonic acid, and if it builds up too much, we know it’s an issue and that’s what causes the pain.

A lack of oxygen, or asphyxiation with nitrogen doesn’t prevent you from exhaling CO2, so the CO2 never builds up. Our bodies also cant detect the levels of oxygen or nitrogen because they don’t form something easy to detect like carbonic acid when they are in our blood.

You can’t actually die of asphyxiation from CO2 because you’d die of CO2 poisoning first. The carbonic acid levels would build too high and start doing damage after overpowering the buffers that keep your pH in check.