The report gives results of a literature review of air infiltration measurements using tracer gases, including sulfur hexafluoride, hydrogen, carbon monoxide, carbon dioxide, nitrous oxide, and radioactive argon and krypton. Sulfur hexafluoride is the tracer gas of choice, primarily because its presence may be accurately measured in the parts per billion range using electron capture/gas chromatography techniques. Most of the other gases used may be accurately measured in the parts per million range using infrared technology. The report describes a computer-controlled injection system.