RDS supplies a medium flow-rate air sampler that is coupled with a filter cassette that contains the 37 mm glass microfiber filter. The RDS Low Background Alpha Counter is used for alpha counting of long-lived dust on the filter. As the background count rate of the alpha counter is very low (typically less that 2 counts per hour) the lowest limit of detection is approximately 5E-5 Bq/m3 of long-lived alpha activity of dust provided the air sampling is carried for 5 days with the flow rate of 1L/min.