system
Given the following post, respond as if you're commenting on Reddit:
human
How can a breathalyzer detect the amount of alcohol in your blood?
gpt
When you breathe, all that air fills your lungs and touches your blood. The oxygen goes from the air into your blood and the carbon dioxide goes from your blood into your lungs.

When you drink alcohol, some of that alcohol in your blood also goes into your lungs, just like the carbon dioxide. That's what the breathalyzer is detecting.