Passive radon radiometers, based on alpha particle etched track detectors,
are very attractive for the assessment of radon exposure. The present revie
w considers various devices used for measurement of the volume activity of
radon isotopes and their daughters and determination of equilibrium coeffic
ients. Such devices can be classified into 8 groups: (i) open or "bare" det
ectors, (ii) open chambers, (iii) Rn-222 chambers with an inlet filter, (iv
) advanced Rn-222 radiometers, (v) multipurpose radiometers, (vi) radiomete
rs based on a combination of etched track detectors and an electrostatic fi
eld, (vii) radiometers based on etched track detectors and activated charco
al and (viii) devices for the measurement of radon isotopes and/or radon da
ughters by means of track parameter measurements. Some of them such as the
open detector and the chamber with an inlet filter have a variety of modifi
cations and are applied widely both in geophysical research and radon dosim
etric surveys. At the same time, some of the radiometers are still in the d
evelopment phase. CR-39 has become the state-of-the-art etched track detect
or for environmental radon. However, due to their ability to work in the op
en mode, cheapness, possibility of utilization of spark track counters and/
or smaller measurement error, other types of alpha particle sensitive detec
tors such as cellulose nitrate (LR 115) or polycarbonate (Makrofol E) are o
ften used for radon measurements in the environment. In the last decade a n
umber of papers devoted to development of multipurpose radiometers, theoret
ical models which enable calculation of the dosimeter response and investig
ation of the permeability of various filters to radon, have been published
and are reviewed. (C) 1999 Elsevier Science Ltd. All rights reserved.