A new arrangement using two sheets of parallel track-etch detectors (T
EDs) in the open metalic holder for Rn measurement in soil is describe
d. The formula for the response of the system was derived and experime
ntally proved as the linear function of the gap width between the shee
ts within the limits 0.5 - 7 mm. The proper choice of the gap width al
lows to optimise the measuring conditions with respect to both the per
iod of application and the expected radon concentration. The features
such as, firmness, small size (outer volume less than 5 cm(3)), simple
and compact construction as well as low costs offer this method as th
e complementary one to the commonly used cup-technique. The preliminar
y calibrations are described and the results of several pilot field me
asurements are presented.