Passive alcobol sensors (PAS) are screening devices designed to sample nonintrusively the ambient air around a driver's mouth to determine the presence of alcohol. Studies have shown that PAS devices can aid police officers in the identification of impaired drivers, particularly at sobriety checkpoints. Data from a 1996 nationwide survey, in which 5,392 drivers were evaluated for alcohol using botb the PAS III (a passive sensor boused in a flasblight) and evidential breath test devices, bave allowed the determination of appropriate criteria at various blood a1cobolconcentrations (BAC) for detecting impaired drivers in the field. Using the appropriate criteria, the PAS III can identify about 75% of the drivers witb BACs at or above 0.10%, and 70% at or above 0.08%. This is a vast improvement over the 40-50% detection rate currently acbieved by police officers at cbeckpoints not using sensors. Using the PAS III few drivers would be identified inappropriately. At the criterion recommended for detecting BACs at or above 0.08%, about 14% of drivers with BACs of O.02-0.05% would be incorrectly identified as having a higher BAC. Field studies have shown that when police officers rely on observation alone about 20% of drivers witb low BACs are detained for further evaluation. More widespread use of passive sensors by police officers would aid in the detection of drinking drivers. Sensors also could provide an additional deterrent to the general public if they believe that when stopped by the police after drinking tbey will be detained for further evaluation.