An environmental radon monitoring system, comprising a radon-chamber, an etching system, and a track counting system, was constructed. The radon chamber is a detector chamber with an internal diameter of58mm and a height of20mmin combination with a CR-39 detector. Carbon is impregnated in the bodies of the detector chamber to avoid problem of an electrostatic charge. The optimized etching condition for the CR-39 exposed to a radon environment turned out to be a 6.25 N,NaOH solution at 70°C during a 7hours' period. According to the calculations, the dosimeter can detect minimum Radon concentration equal to 18.66Bq.m^-3 after 30 days. The bulk etch rate under the optimized condition was 1.14±0.03 μm h^-1. The diameter of the tracks caused by radon and its progeny were found to be in the range of 10~25 μm under the optimized condition. The track images were observed with a track counting system, which consisted of an optical microscope, a color charged couple device (CCD) camera, and an image processor. The calibration factor of this system is obtained to be 0.105 ± 0.006 tracks cm^-2 per Bq m^-3 d.

The calibration factor for optimized conditions was gained150 tracks.cm^-2 (Bq.lit-1.day)^-1.