A passive direct-reading radon monitor utilizing a custom α particle detecting MOS integrated circuit and electrostatic radon progeny concentrator has been designed, built and successfully tested. Radon concentrations at the threshold generally considered hazardous can be detected within hours. This monitor appears suitable for low-cost, high-volume production.

A second generation fast-responding passive radon detector using electrostatic concentration and enhanced readout electronics has been designed, built and tested. This detector utilizes the custom α-detecting IC called αRAM. In order to assess the response time, simulations were performed to analyze the turn-on transient of the detector. In an ambient with constant radon concentration, simulations indicate 1.44 hours will be required for the detector to reach 90% of its maximum count rate. This result is consistent with experimental findings using both first and second generation passive radon detectors.