Utah DUI Intoxilyzers Are Inaccurate Because They Don't Measure Breath Temperature

David Rosenbloom a Utah/Salt Lake City DUI Attorney explains false readings in Intoxilyzer testing.

Why Breath Temperature Matters For Utah DUI Breath Results

Utah DUI Intoxilyzers are calibrated each month by a member of the Utah Highway Patrol trained to carefully control the temperature of the test solution; in fact, they are so concerned about the temperature of the test solutions that they carry them around in a device that plugs into the cigarette lighter of the police cruiser to ensure the solution stays warm at 34 degrees Centigrade. Why!? Because breath temperature is critically important in determining a breath test result; and that conclusion would be correct. Only one huge problem - NONE of the Intoxilyzers owned by the state of Utah have the ability to measure breath temperature, so they settle for a fixed temperature of 34 degrees Centigrade. Which might be suitable if say, you were a Chimpanzee. If however you are testing human breath - each degree of temperature above 34 C equates to a whopping 6.7% higher than actual value! And yes, you guessed it, the average temperature for humans is around 35.7 degrees C; so on average, right off the bat, the Intoxilyzer results are actually about 10% higher (and can be as much as 24% higher) on average than they should be.

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Bell, What About the Humble Mouthpiece? Breath Sample Modification and Implications for Breath Alcohol Analysis, Victoria Forensic Science Centre, B.C. (1991)

The modifying effect of the mouthpiece used in breath alcohol analysis was examined in terms of alcohol concentration in, and temperature of, the sample delivered. With repetitive testing, the standard Disposable Products mouthpiece (generally used for evidential breath analyses in Australia) was examined using a simulated blood alcohol concentration (BAC) of 0.250 g/100mL, delivery flowrate of 12 L/min and delivery volume of 2.5 L. The measured BAC and temperature values for tests with and without a mouthpiece were signicantly different (p< 0.0001) and the differences averaged 0.0020 g/100mL and 1.0 °C respectively. Using an Allplastics brand mouthpiece, the reduction in BAC and temperature were 0.0027 g/100mL and 1.8 °C. Further testing using the Disposable Products mouthpiece pre-warmed (40 °C) and cooled (3 °C), when compared to using a mouthpiece at 20 °C, did not significantly alter BAC, but increased and decreased the measured temperature by 1.0 and 0.6 °C respectively (p<0.0001). The temperature reduction using a Disposable Products mouthpiece and a human subject who provided breath samples in a standardised fashion, was 1.0 °C. The conclusions are that the mouthpiece modifies the breath sample delivered, lowering both BAC and temperature. The variations in BAC and temperature do not correlate with the change in alcohol air/water partition ratio of 6.7% per degree. Therefore, the correction of BAC readings to a standardised temperature (of 34.0 °C) is not straightforward.

Carpenter and Buttram, Breath Temperature: An Alabama Perspective, 9 IACT Newsletter 16, 16 (July 1998)

Dave's Plain English Summary / Synopsis: Mouthpieces lower temperature by 1 degree centigrade, resulting in higher false positives.
1. One reason the Draeger Alcotest is better than Datamaster is because it measures breath temperature
2. Reviewing "Modern" literature 34° is not average. 35.5 ° is average.
3. Schokneckt says 33 - 36.7° range.

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Dubowski, Studies in Breath-Alcohol Analysis: Biological Factors, 76 International Journal of Legal Medicine 93 (1975)

Dave's Plain English Summary / Synopsis: Intoxilyzers that do not measure breath temperature end up reporting higher than normal breath test results as a result of condensation in the mouthpiece with higher than normal expiration samples following plateau of alcohol level.

Various biological factors affecting breath-alcohol analysis were studied experimentally. End-expiratory temperatures in 55 healthy subjects were found to range from 32.41 to 35.69 degrees C with a mean of 34.53 degrees C. Forced vital capacity in the same subjects ranged from 1825 to 6550 ml with a mean of 4038 ml, and maximum exhalation after normal inhalation ranged from 1180 to 4550 ml with a mean of 2730 ml. It was found that 65-70% of available breath must be discarded before the alveolar plateau is reached during expiration. End-expiratory (alveolar) carbon dioxide in 155 healthy subjects was 3.5-8.3% by volume (mean = 6.52). After oral alcohol intake, retained mouth-alcohol in 8 subjects had disappeared after 11 minutes without subsequent water-rinsing of the mouth, and after 8 minutes with rinsing. Water condensation in plastic mouthpieces/saliva traps during breath sampling yielded mean weight gains of 13.0, 8.6, and 4.6 mg., respectively, at initial mouthpiece temperatures of 3 degrees C, 22.5 degrees C, and 34.7 degrees C, respectively.

Abstract courtesy of www.pubmed.org - A service of the National Library of Medicine and the National Institutes of Health

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Fox and Hayward, Effects of Hyperthermia on Breath Alcohol Analysis 34 Journal of Forensic Sciences 320 (1987)

Dave's Plain English Summary / Synopsis: Hyperthermia causes up to a 23% increase of breath alcohol over blood alcohol. 8.62% increase of breath alchol over blood alcohol per degree Celsius increase in core body temperature. Mouth temperature should be measured to allow a temperature correction factor.

ARTICLE

Mild hyperthermia to the extent of a 2.5"C Increase above normal body temperature was produced by immersion of ethanol-intoxicated subjects in a warm water bath. Hyperthermia did not influent- the blood-alcohol decay curve of the subjects. Hyperthermia did cause a significant distortion of the breath-alcohol decay curve, up to as much as a 23% increase above blood-alcohol concentration. The magnitude of this distortion effect was calculated to be a 8.62% increase in breath-alcohol concentration over blood-alcohol concentration for each °C Increase in core body temperature. The forensic relevance of these results is that further support is given to previous recommendations that temperature monitoring be included in procedures for breath-alcohol analysis. This leads to the recommendation that mouth temperature be measured before breath sampling to screen for abnormal body temperature and to allow for potential use of a "temperature correction factor." This modification to existing analytical procedures would optimize the reliability of breath-ethanol analysis for prediction of blood-ethanol concentration.

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SEE ALSO:

Jones, Effect of Temperature and Humidity of Inhaled Air on the Concentration of Ethanol in a Man's Exhaled Breath, 63 Clinical Science 441, 441 (1982)

Jones, Medicolegal Alcohol Determinations - Blood-or Breath-Alcohol Concentrations? 12 Forensic Science Review 23, 42 (Jan. 2000)

McMurray, Breath Temperature and Breath Alcohol Analysis, 20 DWI Journal: Law and Science, 5 (2005)

Ohlson, etal., Accurate Measurement of Blood Alcohol Concentration with Isothermal Rebreathing, 51 (1) Journal of Studies on Alcohol 6 (1990)