Skip to Content

Breath-Alcohol Analysis and "Mouth Alcohol"


Breath alcohol analysis in DUI cases is based on the presumption that breath machines read alveolar air or deep lung air that is reasonably in equilibrium with blood alcohol levels. However, one problem associated with breath machines is that they can also read "mouth alcohol" which can result in contamination of the breath sample and a false high reading.

Mouth alcohol can result from burping, regurgitation, belching or hiccupping. This can carry alcohol from the stomach to the mouth. It can also result from trapped alcohol in dentures or food stuck between the teeth. This alcohol is not from the lungs and therefore does not represent a persons true breath alcohol level.

There are a number of safeguards to avoid this problem including an observation period of at least fifteen minutes prior to a breath test and duplicate analyses. Some machines also have a "slope detector" which, theoretically at least, can recognize mouth alcohol and abort the test.

There are a number of individual issues associated with breath testing and mouth alcohol which will be addressed in future posts.

Many people arrested for drunk driving are surprised by the reading of the breath machine in their case. If a reading seems high and is inconsistent with a persons drinking pattern, it is important to establish why. Do not feel that breath machines are always accurate and that the readings must be accepted.

If you are interested in learning more about this issue or other DUI defenses, please look out for future blogs, or call Nigel Witham at Gold & Witham, 562 938 7771.