Continuous measurements of outdoor 222Rn concentrations for three years at one location in Colorado.

Measurements were made of {sup 222}Rn concentrations outdoors in Ft. Collins, Colorado, using a continuously sampling scintillation flask between January 1993 and December 1995. These data were analyzed for hourly, daily, and seasonal variations. The average {sup 222}Rn concentration at 1 m above the ground was 18 {+-} 10 Bq m{sup {minus}3} with a geometric mean of 15 Bq m{sup {minus}3} and a geometric standard deviation of 1.7. Hourly averaged data indicated a diurnal pattern with the outdoor {sup 222}Rn concentration reaching a maximum in the early morning between 4:00 a.m. and 6:00 a.m. and a broad minimum between 1:00 p.m. and 4:00 p.m. in the afternoon. An analysis also indicated that the outdoor {sup 222}Rn concentrations were consistently lowest during the spring (March and April) and highest during the late summer (July--September).