This publication is one in series of best practice guides for ''Laboratories for the 21st Century,'' a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy Federal Energy Management Program. It is intended for those who plan to design and construct public and private-sector laboratory buildings. This guide provides general information on specifying acceptable exhaust and intake designs. It also provides various quantitative approaches that can be used to determine expected concentration levels resulting from exhaust system emissions.