Mouth Alcohol Detector
I an earlier blog, I mentioned that one problem associated with breath tests in DUI cases was mouth alcohol contamination. Breath machines should "read' alveolar air . However, even a tiny amount of undigested alcohol in the mouth can elevate the breath alcohol reading. This may result from "trapped" mouth alcohol in dentures or food stuck between the teeth, or from alcohol from the stomach entering the mouth as a result of burping or regurgitation.
Most, but not all breath machines have a "slope detector" which is a device intended to measure for mouth alcohol and abort a test if it is present. In theory, mouth alcohol would cause a rapid rise followed by a rapid fall in breath alcohol at the time of the test. This would be inconsistent with the steady rise, peak and leveling off of breath alcohol expected from alveolar air.
However, this is a device that does not work with any acceptable degree of reliability. Additionally, the slope detector is not equipped to measure "trapped" mouth alcohol as opposed to mouth alcohol from belching or burping. The contribution from trapped mouth alcohol is constant during the blow and cannot be detected.