Measurement of the²¹⁴PO concentration in air using Makrofol-DE detectors

The measurement of the 214Po concentration in air with Makrofol-DE detectors is useful to estimate the long-term averaged equilibrium factor indoors. To differentiate α-particles emitted by 214Po from those emitted by 218Po and 222Rn, the detector must register only α-particles with energies between 6.2 and 7.5 MeV. The required energy response is obtained only if a removed layer of about 43 μm is achieved in a chemical etching of the detector. The methodology used to determine the etching conditions is described in this paper. The optimum conditions found are: a) chemical etching for 6 h at a temperature of 40 °C, using 7.5 M KOH mixed with 50 % ethanol as an etchant, and b) electrochemical etching for 1 h at a frequency of 3 kHz and an electric field strength of ∼34 kV cm-1. Several dosimeters have exposed during 2 months in dwellings located in the Barcelona area, Spain. A 214Po averaged concentration of (13.6 ± 8.6) Bq m-3 was obtained. © 1999 Elsevier Science Ltd. All rights reserved.