• Prediction of airborne concentrations of environmentally important contaminants is supported by field test data on tobacco smoke. The analysis discussed herein is completely general in nature, and the contaminants can be gases, vapors, liquid droplets, and solid particulates, including microorganisms and pollens. Several engineering controls can be applied to practical environmental systems to reduce and control undesirable contaminants in normally occupied structures. The use of the method is an important research tool to more accurately quantify airborne contaminant levels in environmental medicine experiments with animals or human subjects. It is difficult and expensive to control inside environmental contaminant levels at values less than 20% to 25% of those occurring outside. The same is true for internally generated contaminants.