Utah DUI Intoxilyzers Are Inaccurate Because They Use a Single Breath Sample, allow for interference and fail to measure temperature:

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; 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, 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 20% higher) on average than they should be just from breath temperature.

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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 : 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. 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. 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.

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Bell, et al., Diethyl Ether Interference with Infrared Breath Analysis, 16 Journal of Analytical Toxicology (1992)

Intoxilyzers are well known to have specificity difficulties (difficulty distinguishing between ethanol -alcohol, and other similarly sized molecules which can fool the machine into a high false positive) due to the large amount of substances having the same wavelength interference as ethanol molecules; this is why every machine has more than just the single “filter” needed to detect ethanol. Abstract courtesy of www.pubmed.org – A service of the National Library of Medicine and the National Institutes of Health
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Bosch, Xavier, Using Asthma Inhalers Can Give False Positive Results in Breath Tests, 324 British Medical Journal, 756 (2002)

Dave’s Plain Language Analysis / Synopsis: Inhalers without ethanol produced false positives for ethanol when subjects given breath tests within 10 minutes. Dr. Ignacio-Garcia suggests that the propellants are the cause.

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Caldwell & Kim, The Response of the Intoxilyzer 5000 to Five Potential Interfering Substances, 42 (6) Journal of Forensic Sciences 1080,(1997)

A study was conducted of potential vapor phase interferents which could be present on human breath and also be capable of inducing a false-positive response for ethanol on the evidential infrared-based breath testing device. All compounds tested were found to be capable of inducing false-positive readings for ethanol in a highly reproducible manner, as a result of which it has been possible to derive precise least-squares equations describing the ethanol readout expected for any given blood concentration. Abstract courtesy of www.pubmed.org – A service of the National Library of Medicine and the National Institutes of Health
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Giguiere, Lewis, Baselt, Chang, Lacquer fumes and the Intoxilyzer, 12 Journal of Analytical Toxicology 168, 168 (1988)

Dave’s Plain Language Analysis / Synopsis: Painter blows a .075 on Intoxilizer after painting with lacquer fumes for 20 minutes with mask. Then another ten minutes without mask blew .48
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Janhanen, Baraona, Hiyakawa, and Lieber, Origin of Breath Acetaldehyde During Ehtanol Oxidation: Effects of Long-Term Cigarette Smoking, 100 Journal of Laboratory Clinical Medicine 908 (1982)

Dave’s Plain Language Analysis / Synopsis: Acetaldehyde greater than would be expected if just passing from liver to lungs via blood.
Acetaldehyde was greater in the lungs for smokers than non smokers.
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Krotosyynski, Gabriel, O’Neil & Claudio; Characterization of Human Expired Air: A Promising Investigation and Diagnostic Technique, 15 Journal of Chromatographic Science 239 (1977)

Dave’s Plain Language Analysis / Synopsis:  Perhaps as much as 50% of the population have substances on their breath that can “fool” the machine into reporting high breath alcohol concentrations.
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Labianca, How Specific for Ethanol is Breath-Alcohol Analysis Based on Absorption of IR Radiation at 9.5 um? 16 Journal of Analytical Toxicology 404, 405 (Nov.-Dec. 1992)

Dave’s Plain Language Analysis / Synopsis: Breath testing lacks of specificity because thousands of organic molecules that contain the methyl group and the corresponding carbon-hydrogen bond absorb the light producing false positives.

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Logan & Distefano; Ethanol Content of Various Foods and Soft Drinks and their Potential for Interference with a Breath-Alcohol Test, 22 Journal of Analytical Toxicology 181 (1988),

Dave’s Plain Language Analysis / Synopsis: Datamaster Intoxilyzer read up to .046 on bread etc. The mouth alcohol Slope detector failed.

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Stowell, et al., A Reinvestigation of the Usefulness of Breath Analysis in the Determination of Blood Acetaldehyde Concentrations, 8 Alcoholism: Clinical and Experimental Research 442 (1984)
Dave’s Plain Language Analysis / Synopsis: Acetaldehyde was coming not from the liver but the lungs! Showing BAC 30 times higher than actual result. Abstract courtesy of www.pubmed.org – A service of the National Library of Medicine and the National Institutes of Health
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