Citation

Schmidt M, Hattendorff HD. Proc. Int. Counc. Alcohol Drugs Traffic Safety Conf. 1982; 1982: 179-185.

Copyright

(Copyright © 1982, The author(s) and the Council, Publisher International Council on Alcohol, Drugs and Traffic Safety)

DOI

unavailable

PMID

unavailable

Abstract

A customary method of simulating breath alcohol is bubbling air through an aqueous alcohol solution of proper concentration at 34 deg C. The decrease of the alcohol concentration of the solution and hence of the test gas has been calculated as a function of the air throughput. In simulators with one chamber the alcohol concentration decreases exponentially from the initial value. There is also an uncertainty whether the alcohol concentration in the air is in equilibrium with the alcohol concentration of the solution. Improved accuracy is achieved by dividing the solution between two chambers and connecting the gas outlet of the first chamber to the gas inlet of the second. The calculated decrease of the alcohol concentration of the test gas is considerably less than for one chamber up to high air throughput volume. The decrease might be less than 6% when performing 100 tests with the A.L.E.R.T. alcohol screening tester using 2 x 250 ml alcohol solution. The calculated decrease has been checked experimentally, using a precise infrared breath alcohol testing device (the Drager Alcytron). The experimental values agree well with the calculation. Dividing the alcohol solution among more than two chambers leads to even improved long-term stability of the test gas alcohol concentration up to a critical air throughput volume. At higher throughput volumes the alcohol concentration will quickly drop to lower values. In practical use the two-chamber simulator is the best compromise between the accuracy and stability of the test gas alcohol concentration and the ease of handling and price.