How does alcohol get into your breath?

When a person drinks alcohol, the alcohol is absorbed throughout all the water-bearing tissue in a person’s body, including the blood.  Deep in our lungs, as a part of the respiration process, a tiny amount of alcohol “evaporates” from the blood into the lungs.  When a person exhales, the alcohol that “evaporated” from the blood appears in their breath.  Scientists have established (Henry’s Law) that the ratio of alcohol in breath and alcohol in blood is consistent, 1:2100.  Therefore, a breath test gives an accurate measure of intoxication levels.