Abstract: An IR cell for the detection and measurement of breath alcohol is standardized by passing a dry gas carrier containing a known amount of alcohol through an IR cell the walls exposed to the standardizing mixture of which are, as to the alcohol, non-adsorbent.

Abstract: A method of measuring breath alcohol includes blowing breath in a stream through an inlet line, hence through an orifice, past a thermistor exposed to the stream, changing the temperature of the thermistor to a predetermined temperature in response to a predetermined volume of breath. The thermistor provides an output signal to trigger the measurement of alcohol in the breath by an alcohol detecting device. The method and apparatus permit the purging of the system to provide a base line reference for the alcohol detection device, then testing to ensure that the breath inlet line is clear of contamination, then running an alcohol standard sample through the alcohol detecting device, again purging the system, again testing to ensure that the breath inlet line is clear of contamination, recording the result as a blank test, and thereafter blowing breath through the inlet line to obtain a demonstratably accurate measurement of breath alcohol.

Abstract: A method and apparatus for discriminating between alcohol and acetone in a breath sample and accurately measuring the alcohol level when acetone is present in the sample. The breath sample is measured with two different types of detectors and their outputs compared. One detector uses the principles of infrared (IR) absorption, the other detector is a semiconductor, commonly called a Taguci cell, or its equivalent. Automatic correction is provided for variations in sensitivity of the semiconductor.