[Comparison of breath and blood alcohol concentration from measurements in police work]

4.135 measurements of breath- and blood-alcohol concentration were performed by police in 1986 and 1987 using the Alcomat A 11 (wavelength 3.4 microns). Important conclusions from these measurements can be derived with regard to legal breath-alcohol limits. The parameter for judgement is the breath- to blood-alcohol concentration ratio. Extreme deviations which have to be considered as malfunctions were found only in 0.4% of all cases, despite of the fact that not all precautions for evidential measurements are fulfilled. The reasons for malfunction may result from faulty breath- or blood-alcohol determinations or may simply be errors of transfer. The frequency of relatively too high breath-alcohol values (e.g. by interfering substances) is nearly the same as of relatively too low values (e.g. by too small breath volume). It has to be considered that the requirements according to the expertise of the Federal Health Office for evidential breath-alcohol measurements are only fulfilled partly. Especially the influence of breath-temperature is disregarded although the influence on frequency distributions is important as the comparison with other measurements demonstrates. A further result shows that the frequency distribution of the breath- to blood-alcohol ratio does not depend on blood-alcohol values.