Published with permission from the book, DUI/DWI: The History of Driving Under the Influence, David N. Jolly. Outskirts Press (2009)
The DUI Guide Preliminary Breath Testing Devices (PBTs)
The majority of the preliminary breath test machines (handheld units) utilize an electrochemical fuel cell technology the technology fits in the smaller and more compact handheld units. The disadvantage of these units is that they are less reliable and accurate that the larger table top versions that use IR technology. Despite issues over reliability and accuracy these hand held screening devices are popular for use as a screening tool to detect the presence of alcohol.
There are a number of different PBT models in use for DUI purposes. The more popular models include the Intoxilyzer S-D2 and Intoxilyzer S-D5 (both manufactured by CMI Inc.), and the AlcoSensor III and AlcoSensor IV PBT Device (both manufacturedby Intoximeters Inc. of St. Louis, Missouri).
The arguments against the fuel cell technology are many. The first is that this technology is not specific to ethanol only and as a result a PBT reading can provide innaccurate results. One study found that an “Alcolmeter Pocket Model” reacted positively to ethanol but it also reacted to acetaldehyde, methanol, isopropanol, and n-propranolol. Jones, Alan W. and Goldberg, L. Evaluation of Breath Alcohol Instruments I: In Vitro Experiments with Alcolmeter Pocket Model. 12 Forensic Science International 1 (1978)
Other issues with fuel cell technology and their accuracy and reliablity is that the devices are susceptible to weather extremes. NHTSA issued the following warning regarding the AlcoSensor IV without a heated cell:
If the ambient air is cold enough, and if the hand held breath tester is unheated, it is possible for the moisture in the breath to condense onto the airway surface of the tester, and cause alcohol present to condense with it. It has been pointed out to NHTSA that if this condensation occurs, it is possible for alcohol in one test to carry over to a second test, which would cause a false positive result. U.S. Dept. of Transp. NHTSA. Special Testing for Possible Carry Over Effects Using the Intoximeters Inc. Alco Sensor IV at 10 Degrees Centigrade. DOT HS 809 424 (March 2002)
In the United States, NHTSA maintains a "Conforming Products List" of breath alcohol devices approved for preliminary screening use. Highway Safety Programs; Conforming Products List of Screening Devices to Measure Alcohol in Bodily Fluids. DOT, NHTSA. Federal Register, Volume 72, No. 20 (January, 2007) Similarly, in Canada, a preliminary non-evidentiary screening device can be approved by Parliament as an approved screening device.