In 2017, approximately 57.3 million gallons of retardant was loaded onto airtankers. Of that, approximately 19 million gallons were dropped onto NFS lands. The use of fire chemicals is not without controversy. This presentation will summarize the various categories of wildland fire chemicals, their characteristics, and the environmental implications of their use.Aerial delivery systems are utilized to distribute fire chemicals, primarily retardant, on the landscape. Knowledge of drop patterns, parameters influencing those patterns, application tactics and reasons for line failure will also be discussed.