[en] Atmospheric tracer techniques are reviewed, with emphasis on the Hanford inert gas krypton-85 field technique. This technique is considerably more sophisticated than the visible and particulate tracer techniques. The krypton technique develops histories of concentration at up to 128 field locations; the particulate techniques generate only bulk time integrated samples. The krypton dispersal technique permits release of either a plume or a true puff; the particulate techniques permit continuous releases, but only approximations of puffs through short continuous releases. The Hanford krypton-85 inert gas system offers the advantages of an inert gas tracer, permits release of either puffs or plumes, and presents histories of concentration as opposed to only time-integrated concentrations. However, the approach used has the disadvantages of being usable at only short distances, is a relatively expensive system to deploy and maintain, and is restricted as to locations where it may be used due to the radioactive nature of the tracer