A tracer method for evaluating recirculation of pollutant releases in buildings

A method is introduced for evaluating recirculation in a building ventilation system from pollutant emissions in or near the building. Tracer was released at a known rate at the point of pollutant emission. Using measured tracer concentrations, the tracer release rate, and an estimate of the pollutant release rate, pollutant concentrations were estimated at the locations in the building where the tracer was measured. The method can be used to test whether a ventilation system is adequate for maintaining an acceptable work environment before work with a hazardous substance begins. In a case study presented to illustrate the technique, initial attempts to correct a problem of recirculation of sulfuric acid from a fume hood in a chemistry laboratory were shown to be inadequate, prompting the ventilation contractor to make further repairs before work with sulfuric acid could be resumed.