The Accuracy of Evidential Breath Testers at Low BACs

Frank, James F.; Flores, Arthur L. · 1989 · ROSA P / United States. National Highway Traffic Safety Administration

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Summary

This technical note addresses concerns regarding the accuracy of evidential breath testers (EBTs) at low blood alcohol concentrations (BACs), specifically below 0.050%. The study was motivated by recent research indicating that alcohol levels as low as 0.050% may impair driving-related skills, raising questions among law enforcement about the reliability of their testing devices at these lower thresholds. The objective was to determine if EBTs maintain the same level of accuracy at low BACs as they do at higher, legally significant levels. The researchers conducted laboratory testing on seven widely used EBT models, which represent at least 60% of units used by police for drinking and driving enforcement. The devices included the Alco-Sensor III, BAC Verifier, Intoxilyzer 4011AS-A, Intoxilyzer 5000, Intoximeter 3000, Lion Alcometer S-D2, and Smith & Wesson Breathalyzer 2000. Each unit was tested ten times against simulated BACs of 0.010%, 0.020%, 0.030%, 0.040%, and 0.100%. Simulated alcohol vapor was generated using a Smith & Wesson Calibrating Unit compliant with NHTSA specifications. The performance was evaluated against NHTSA model specifications, which require accuracy within ±0.005% BAC (or ±5%, whichever is greater) at standard test levels of 0.050%, 0.100%, and 0.150%. The results demonstrated that all seven devices met the ±0.005% BAC accuracy requirements at simulated BACs of 0.030% and above. At the 0.020% level, six of the seven devices met the accuracy requirements. However, at the 0.010% level, two devices produced readings between 0 and 0.005%, suggesting potential failure to detect alcohol at this very low concentration. Additionally, testing with non-alcoholic samples (0.00% BAC) showed that the devices did not produce false positive readings, with the exception of the Alco-Sensor III, which recorded ten consecutive readings of 0.001% BAC. The study concludes that evidential breath testers perform with the same accuracy at BACs of 0.020% and above as they do at higher levels tested against NHTSA guidelines. This finding provides confidence in the reliability of these devices for law enforcement purposes at low alcohol concentrations. The authors note that while the devices are technically accurate, their high-quality performance in the field depends on proper maintenance and use by trained operators.

Key finding

Seven evidential breath testers met NHTSA accuracy specifications at simulated BACs of 0.030% and above, and six devices met specifications at 0.020% BAC.

Methodology

lab_experiment

Sample size: 7

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• alcohol detection systems