Notes that drift loss from cooling towers may transmit legionnaires' disease. Measurement of drift loss is essential to reducing infection. Briefly describes the alternatives for drift loss measurement. Describes a new, indirect method which, with additional sample of circulating water and more rigorous equations avoids errors due to tracer in the makeup water and surroundings. Notes that the international standard for potentiometric titrations, with silver nitrate allows precise and accurate analysis of chloride ion tracer. States this modified chloride balance is easy, practical and accurate for drift loss measurement.

KEYWORDS: Cooling towers, aerosols, legionnaires disease, measuring, infectious diseases, chlorides, sodium compounds, ions, tracers, accuracy