https://www.mdu.se/

In screening applications there is a need forimproved breath alcohol analyzers. Accuracy, specificity,usability, and through-put are critical to the device performance. Objective: To characterize the critical performance of a newcontactless breath alcohol analyzer. Methods: The device ischaracterized by measurements using artificial breath gas andhuman subjects. Breath sampling is performed in ambient airusing carbon dioxide as a biomarker. Results: Resolution andinter-individual variation, response time, and specificity wereshown to meet the requirements of industrial standards. Thefeasibility of contactless measurement was demonstrated. Conclusions: The new device exhibits sufficient performance inmoderately diluted breath samples. Further work is underway toreach the objective of unobtrusive breath alcohol analysis.

The study objective was to evaluate a novel method and technology for unobtrusive determination of breath alcohol in relation to current industrial accuracy standards. The methodology uses carbon dioxide as a tracer gas detected by sensor technology based on infrared spectroscopy. Part one of the investigation was to analyse the performance of hand-held prototype devices and included tests of resolution, unit-to-unit variation during calibration, response to alcohol containing gas pulses created with a wet gas simulator, and cross sensitivity to other substances. In part two of the study, 30 human participants provided 1465 breath tests in both unobtrusive and obtrusive use modes. The results of both parts of the study indicate that the prototype devices exceeded present industrial accuracy requirements. The proposed methodology and technology eliminate the previous contradiction between unobtrusiveness and high accuracy.

Although the vast majority of vehicle drivers are sober, drunk driving remains to be a major contributor to fatal accidents. Massive deployment of unobtrusive breath alcohol sensing systems could potentially save tens of thousands of lives worldwide every year by preventing drunk driving [1]. The work reported here is ultimately aiming at such a system. The technical performance of the present sensing system with respect to automotive requirements is summarized, and new results towards unobtrusive breath alcohol determination within vehicle compartments are presented. Breath alcohol concentration (BrAC) can be determined unobtrusively if (i) the sensing system provides real-time signals with adequate accuracy corresponding to the local concentrations of both alcohol and a tracer gas, e g CO2, (ii) the dilution of the breath is not excessive in relation to background concentrations, (iii) the sensor location can be seamlessly integrated into the interior of a vehicle cabin. All three of these aspects are addressed in the present paper. More than a hundred prototypes based on infrared spectroscopy were fabricated and subjected to automotive qualification tests in the full temperature range -40 … +85?C. In the majority of tests, adequate performance was noted. Measures are now being taken to fill remaining performance gaps. Test results with human subjects were positive and in accordance with expectations with respect to physiological variations. In-vehicle tests showed that for the best sensor position, passive breath samples allowed BrAC to be determined at a resolution of 2-4% of the US legal limit, providing proof-of-principle for unobtrusive testing. Nevertheless, vehicle integration remains to be the major technological challenge to the objective of deployment on a large scale of unobtrusive driver breath alcohol determination. The feasibility of unobtrusive breath alcohol determination in vehicles, and adequate performance of a sensor system based on infrared spectroscopy have been experimentally demonstrated. The alcohol sensing system may advantageously be integrated into vehicles, and may also be combined with other technologies to monitor driver impairment.

Breath alcohol screening is important for traffic safety, access control and other areas of health promotion. A family of sensor devices useful for these purposes is being developed and evaluated. This paper is focusing on algorithms for the determination of breath alcohol concentration in diluted breath samples using carbon dioxide to compensate for the dilution. The examined algorithms make use of signal averaging, weighting and personalization to reduce estimation errors. Evaluation has been performed by using data from a previously conducted human study. It is concluded that these features in combination will significantly reduce the random error compared to the signal averaging algorithm taken alone.

Objective: The research objective of the present investigation is to demonstrate the present status of passive in-vehicle driver breath alcohol detection and highlight the necessary conditions for large-scale implementation of such a system. Completely passive detection has remained a challenge mainly because of the requirements on signal resolution combined with the constraints of vehicle integration. The work is part of the Driver Alcohol Detection System for Safety (DADSS) program aiming at massive deployment of alcohol sensing systems that could potentially save thousands of American lives annually.

Method: The work reported here builds on earlier investigations, in which it has been shown that detection of alcohol vapor in the proximity of a human subject may be traced to that subject by means of simultaneous recording of carbon dioxide (CO2) at the same location. Sensors based on infrared spectroscopy were developed to detect and quantify low concentrations of alcohol and CO2. In the present investigation, alcohol and CO2 were recorded at various locations in a vehicle cabin while human subjects were performing normal in-step procedures and driving preparations. A video camera directed to the driver position was recording images of the driver's upper body parts, including the face, and the images were analyzed with respect to features of significance to the breathing behavior and breath detection, such as mouth opening and head direction.

Results: Improvement of the sensor system with respect to signal resolution including algorithm and software development, and fusion of the sensor and camera signals was successfully implemented and tested before starting the human study. In addition, experimental tests and simulations were performed with the purpose of connecting human subject data with repeatable experimental conditions. The results include occurrence statistics of detected breaths by signal peaks of CO2 and alcohol. From the statistical data, the accuracy of breath alcohol estimation and timing related to initial driver routines (door opening, taking a seat, door closure, buckling up, etc.) can be estimated.The investigation confirmed the feasibility of passive driver breath alcohol detection using our present system. Trade-offs between timing and sensor signal resolution requirements will become critical. Further improvement of sensor resolution and system ruggedness is required before the results can be industrialized.

Conclusions: It is concluded that a further important step toward completely passive detection of driver breath alcohol has been taken. If required, the sniffer function with alcohol detection capability can be combined with a subsequent highly accurate breath test to confirm the driver's legal status using the same sensor device. The study is relevant to crash avoidance, in particular driver monitoring systems and driver-vehicle interface design.