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ABSTRACTIt is well known that volatile substances on the breath of test subjects have the potential to interfere with infrared-based breath alcohol testing instruments. This case report involves a 68-year-old male who was arrested for suspected alcohol-impaired driving. He worked for a company where he was exposed to acetone and toluene. The subject ultimately provided two breath samples into the Intoxilyzer® 8000C resulting in two “Interferent Detect” messages. Subsequent analysis of a blood sample using headspace gas chromatography detected: ethanol at 101 mg/100 mL, acetone at 17 mg/100 mL, isopropanol at 10 mg/100 mL, methanol at 26 mg/100 mL and toluene (<2.5 mg/L). This case provides an example of two “Interferent Detect” messages obtained from a driver and demonstrates the ability of the Intoxilyzer® 8000C to detect the presence of volatile substances other than ethanol on the breath of a drinking driver.

ABSTRACTRetrospective analysis of the incidence of Radio Frequency Interference (RFI) exception messages obtained during testing of suspected impaired drivers on the Intoxilyzer® 5000C over a 13-year period (1997 to 2009) was examined in order to address concerns on the hypothetical impact of RFI on breath alcohol testing. RFI messages were rare, occurring in less than 0.48% (n = 128) of the 26,939 drivers tested. Multiple RFI messages were even more infrequent, occurring in only 10.2% of RFI-positive cases (n = 13). There was no significant effect of the incidence of RFI messages attributable to a particular testing location (p = 0.98), a specific instrument (p = 0.98), or year of testing (p = 0.99). In addition, the data show no evidence that hypothetical “undetected” RFI events, in addition to those already detected by the instrument, affected either the calibration check results or the subject breath tests in this study. Instruments are designed with an RFI detection system and shielding to protect the internal electronics against RFI. The breath testing procedure requiring two tests in good agreement (within 20 mg/100 mL truncated) is an additional safeguard against “undetected” RFI impacting the tests, and serves to increase the scientific confidence in the results obtained.