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Alcohol breath testing on a larger scale will save lives. Alcohol abuse is a major contributor to death and disease. Alcohol intake affects the human body by significantly longer response time to external stimuli. In situations where the senses need to be on alert this delay can be the difference between life and death. To make the alcohol breath test more available in everyday use, the mouthpiece has been removed. Instead, the exhaled alcohol is measured directly in a diluted sample. The dilution can be accounted for by simultaneous measurement of an endogenous tracer gas. Because of the lack of a mouthpiece several additional factors influence the alcohol measurement, e.g. the obvious lower abundance of analyte gas, shorter time of analysis and physiological aspects of the tracer gas. My studies include sensor development and validation through laboratory experiments as well as human subject studies. Several sensor parameters are crucial for the functionality of the alcohol detection system and are in need of careful investigation. Human behaviour and physiology also needs further understanding. A better understanding of the system provides vital knowledge for the design of smarter algorithms. Planning, conducting and evaluation of these studies lie within the scope of the licentiate thesis.

Alcohol breath testing on a larger scale will save lives. Alcohol intake affects the human body by significantly longer response time to external stimuli. In demanding situations where the senses need to be on alert a prolonged reaction time can be the difference between life and death, both for the intoxicated subject and for surrounding  individuals.

The aims of this thesis include investigations of a new type of breath alcohol sensor, designed for operation without a mouthpiece, both with regards to sensor performance as well as usability in relation to various breath  alcohol  screening applications.

In many situations where breath alcohol screening is suitable, there is a need for quick and easy use. The instrument should interfere as little as possible with the regular routines and procedures. One such task is driving. To accommodate for these needs in an in-vehicle application, the breath alcohol sensing system must be seamlessly installed in the vehicle and not interfere with the normal behavior of the sober driver. Driving is also a task requiring high level of concentration over a prolonged period of time. In the U.S. alone thousands of lives are annually lost in accidents where the driver was under the influence of  alcohol.  Similar numbers have been recorded for Europe. The potential for a system handling the needs for ease-of-use is huge and may result in successful products.

The results presented within this thesis provide experimental evidence of sufficient sensor performance for screening applications with an instrument operating without a mouthpiece. Smarter calculation methods were also shown to be a feasible path to improved measurement reliability. Important steps towards an even more passive solution for in-vehicle screening is also presented. Experiments showed that given enough time and sensor resolution, passive alcohol detection systems are feasible.