A flow-mode integrated sampler consisting of a wire-mesh and filter-paper array along with passive solid state nuclear track detectors has been developed for estimating unattached and attached fraction of ²²²Rn/²²⁰Rn progeny concentration. The essential element of this sampler is the direct ²²²Rn/²²⁰Rn progeny sensor (DRPS/DTPS), which is an absorber-mounted-LR115 type nuclear track detector that selectively registers the alpha particles emitted from the progeny deposited on its surface. During sampling at a specified flow-rate, the unattached progeny is captured on the wire-mesh; while the attached progeny gets transmitted and is captured on the filter-paper. The alpha particles emitted by the deposited progeny atoms are registered on the sensors placed at a specified distance facing the wire-mesh and the filter-paper, respectively. The various steps involved in the development of this flow-mode direct progeny sampler such as the optimization of the sampling rate and the distance between the sensor and the deposition substrate are discussed. The sensitivity factor of the DTPS-loaded sampler for ²²⁰Rn progeny deposited on the wire-mesh and filter-paper is found to be 23.77 ± 0.64 (track cm^-2 h^-1) (Bq m^-3)^-1 and 22.30 ± 0.18 (track cm^-2 h^-1) (Bq m^-3)^-1, respectively; while that of DRPS-loaded sampler for ²²²Rn progeny deposition, is 3.03 ± 0.14 (track cm^-2 h^-1) (Bq m^-3)^-1 and 2.08 ± 0.07 (track cm^-2 h^-1) (Bq m^-3)^-1, respectively. The highlight of this flow-mode sampler is its high sensitivity and that it utilizes the passive technique for estimating the unattached and attached progeny concentration, thus doing away with the alpha counting procedures.