That’s right.  What these machines actually detect and measure is any chemical compund that contains the methyl group in its molecular structure. There are thousands of such compounds — including quite a few which can be found on the human breath. And this machine that determines a person’s guilt or innocence will “see” all of those [...]

Read the complete post at http://www.duiblog.com/2008/01/26/breathalyzers-dont-measure-alcohol/