REDUCTION OF CROSS-SENSITIVITY OF INFRARED ALCOHOL BREATH TESTERS USING DOUBLE FILTER TECHNIQUE IN THE 10 urn RANGE

The cross-sensitivity of breath-alcohol analysing systems is intensively discussed since these instruments are used for evidential breath testing. Besides ethanol other substances can be present in human breath at significant concentrations. In the beginning of the design of such instruments most of the interest was concentrated only on aceton, which can be found in the breath of subjects, who are suffering from diabetics or have fasted for along period of time [1]. But also a large variety of other compounds may occur in the human breath like organic compounds inhaled in the working process or through the deliberate abuse of solvents evaporating from paints and glue, or like methanol after drinking at high levels for several days, even after blood ethanol levels are no longer measurable. Unfortunately, the highly specific analysing techniques for blood samples, like gas-chromatography, are complex to handle or require frequent calibration and are therefore restricted to laboratory use only.