Unobtrusive Breath Testing

Background: Breath testing today requires cooperation, significant physical effort, and is time-consuming. In order to reach an increased acceptance for general breath testing among drivers and professionals whose sobriety is of importance for a safe work environment, a less obtrusive breath testing procedure is desirable.

Aim: The aim has been to develop a breath alcohol analyser enabling fast, simple contact free breath testing with less physical effort. The sensor should meet the automotive industry’s requirements of long-time stability, and short start-up and response time, regardless of the ambient temperature. The long term goal is extensive implementation of an in-vehicle integrated unobtrusive alcohol detection system.

Results: The physiological rationale of the use of CO2 as a tracer gas has been investigated, and a new non-dispersive infrared gas senor enabling measurements of both breath alcohol and expired CO2 have been developed. The gas sensor has been evaluated with excellent results in sensitivity, cross-sensitivity. In a controlled drinking study a strong correlation (r=0.95) was found between reference tests and tests performed from a distance of a few centimetres with the new sensor. As proof-of-principle of unobtrusive breath testing we have now shown detection of normal human mouth and nose breathing, and artificial gas pulses containing alcohol from a distance over 60 cm in a vehicle compartment.

Future: To improve sampling of the driver’s breath, future work focuses on optimised signal acquisition and selection of positions within the vehicle compartment. Present challenges and important input to this work will be the influence from external air flows (ventilation), difference in breathing pattern (mouth/nose), passengers, and e.g. wind shield fluid. The sensor also provides possibilities to other applications, e.g. for access and passage control.