Discusses five different models for predicting air infiltration. Presents a new model developed at the Institute of Gas Technology. The model is based on the results of tests to obtain the contribution of the existence of a chimney, and furnace operation, to house air infiltration. Reports verification of model by simulating results from 23 test homes. Concludes that model simulates with reasonable accuracy the measured values for a single-storey home equipped with an oil-fired central furnace.