This paper deals with the problem of exhaust cross-contamination between vehicles in a slow-moving traffic queue, as would be found in a busy modern city. This study has been undertaken using an open-jet wind tunnel, to determine the level of exhaust contamination around a 1:10 scale model car under various prevailing wind conditions. Tracer-gas techniques have been combined with static pressure measurements, to model the flow of pollutants around a vehicle body.

Local age of air and air change effectiveness were determined in two office buildings using tracer gas techniques to study the air applicability of the associated measurement procedures in mechanically ventilated office buildings. Measurement issues examined include the establishment of a uniform tracer gas concentration at the start of the test and the relationship of ventilation system configuration and system operation to the test procedure.

Plants have been used as initial indicators, or monitors, of air pollutants around industrial sources for a long time (Heck, 1966). Sulfur dioxide (S02) was early identified as causing injury to field-grown plants (Thomas, 1951; Zimmerman & Hitchcock, 1956).