An improved portable breath measurement method has been developed that allows one-minute sampling times. The equipment has been successfully tested in field and chamber studies. Results of these studies suggest that breath levels following known exposures are predictable and reproducible across a small number of volunteers. The residence times in the body and the distribution in body compartments of several common air toxics have been determined. A simple four-compartment linear model is capable of fitting the observed data. The main parameters of the model include the fraction f of the parent compound exhaled under steady-state conditions and the residence times tau(sub i) in the ith compartment. The values of these parameters for several volatile organic compounds (VOCs) and for the four body compartments (blood, vessel-rich tissues, vessel-poor tissues, and fat) are provided.