More on Breath Temperature

     As far back as the 1930’s it was recognized that re-eqilibration of the alcohol and breath occurs at the lower temperature (as opposed to core body temperature) of the upper respiratory tract during expiration in such a manner that temperature controls the alcohol content of the expired alveolar air.  In the earliest “drunk-o-meter” invented by Professor Rolla Harger of Indiana University it was assumed that 61.5% of the collected breath sample was alveolar air and that 2100:1 was the appropriate partition ratio.  Partition ratio in this instance refers to the amount of alcohol in the blood compared to the amount in the breath.

     During a twenty-year period he and his colleagues conducted numerous experiments, which confirmed that the partition ratio varies at different temperatures.  In other words, breath alcohol test results will be different at different temperatures.  During all of this testing it was assumed that the average expired breath temperature was 34 degrees centigrade (Celsius), which in turn led to the conclusion that the average blood:breath partition ratio for breath alcohol testing is 2100:1.  The National Safety Council adopted this number in 1952, and so it has become engraved in the statutes of the several states over the last half century. 

     Researchers have questioned the use of a constant breath temperature and partition ratio since at least 1975.  Beginning in that year leader experts in the field began to question whether airway alcohol exchange played a bigger role in breath alcohol testing than was previously recognized.  More and more research has proven that the average expired breath temperature is closer to 35 degrees Celsius, including the German study of 1995 and a similar study sponsored by the Alabama Department of Public Safety three years later.

     As a result of the Alabama study that state adopted the Draeger 7110, which makes an adjustment for an elevated breath temperature.  In fact, the Alabama testing sequence includes two breath samples (like Georgia), two methods of analysis for every breath test, specifically infrared and fuel cell (unlike Georgia), breath temperature monitoring and correction for each breath test (unlike Georgia), and two calibration checks at .02 and .08 at the time of each breath test (unlike Georgia).  In addition, a comprehensive data collection package including breath exhalation profiles was included in the software designed for Alabama DPS (unlike Georgia).  The downloaded data includes a total review of all breath tests in the State (unlike Georgia).   This enables the state to identify and address both instrumental and operational problems.  In Georgia there is a handwritten log on which officers may make entries, but nobody knows how often it is used or how often it is ignored. 

     The Alabama program is truly a model program other states should emulate.  Before switching to the Draeger, Alabama (like Georgia) used the Inoxilyzer 5000.  That makes me wonder: If it’s not good enough for Alabama, why are we still using it?

Written by Allen Trapp who is board certified by the National College for DUI Defense and the author of Georgia DUI Survival Guide Visit Website Written by Allen Trapp who is board certified by the National College for DUI Defense and the author of Georgia DUI Survival Guide Visit Website

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