Monitoring of workplaces is the first step of the monitoring of radiation hazard in coal mines. Decision concerning application of individual dosimetry is taken on the basis of the results of workplace monitoring. The system applies to all sources of natural radiation in coal mines.
The workplace monitoring is performed at certain preselected points, usually in one air stream while miners change their position during their work. Therefore, a question arises how far one can relay on workplace monitoring when making decision on application of personal dosimetry and when evaluating individual radiation doses.
The results of investigations concerning this question are presented in this paper. Results of measurements of radon daughters concentrations at workplaces obtained by ALFA-31 sampling probes and dust samplers are compared with the results of individual exposures measured by active French individual dosimeters and by passive track detectors used as individual dosimeters and for workplace monitoring by the Institute of Occupational Medicine (IOM) in Łódź.
The readouts of detectors were performed by its owners: IOM Łódź, Centre de Radioprotection dans les Mines (CRPM) - France and Central Mining Institute (CMI).
The presented results have been obtained in two independent coal mines in Upper Silesia - Ziemowit and Jankowice - during 1991-1992. The results obtained by passive dosimeters (IOM track detectors) were by 1-2 orders of magnitude higher than the results of measurements carried out by active dosimeters (CRPM and CMI).