**2. Radon measurement**

Radon is measured by a wide range of techniques developed over years and improved in sensitivity, portability, and performance parameters [14]. The radon measurement technique mostly depends on the concentration of radon-222 and the characteristics used to classify them as follows:

• whether the technique measures radon-222 and radon progeny

*An Overview of Radon Emanation Measurement System for South African Communities DOI: http://dx.doi.org/10.5772/intechopen.109065*


An alpha particle detected can be used to measure radon-222 decay products by using scintillation counters. Conversely, in the measurement of radon-222, gamma rays emitted from radon-222 daughters can be used to determine or measure radon-222, for example, bismuth-214 and lead-214 [15].

Time resolution sampling analysis and measurement are classified into three techniques, namely grab sampling, continuous technique, and integrating technique. Integrating technique utilizes passive detectors to measure the integrated radon-222 concentration annually or monthly mostly in buildings. Continuous technique provides the simultaneous act of sampling and determination of radon-222 in samples of soil or water in minutes, hours, and days with a device such as scintillation radon monitors and smart radon duo. Grab sampling technique includes the collection of samples of groundwater air samples, in a short time whereby devices such as RAD7 are used to measure radon-222 in samples collected. Awhida [16] states that radon measurement technique differs to the point that one technique cannot meet the requirement such as radon survey type, environmental parameter measurement, and cost of the apparatus.

#### **2.1 Determination of radon-222 by its progeny**

Baskaran [17] states that the decay of 222Rn leads to the formation of numerous radon-222 progenies before 210Pb:

222Rn (3.82) → 218Po(3.10 min) → 214Pb(26.8 min) → 214Bi(19.7 min) →

214Po(40.2 min) → 210Pb(22.3 yr) → 210Bi(5.0d) → 210Po (138.4d).

All the progenies of 222Rn are metals, and the longest-lived progeny is 214Pb. Polonium(Pb) and bismuth (Bi) are particle reactive and attach to atmospheric aerosol particles. 222Rn concentration can be determined from the activity concentration of its progenies. Using Geiger Muller counter, 222Rn activity concentration can be determined from the alpha particles of progenies such as 218Po (6.002 MeV), 214Po (7.687 MeV) or 214Bi (βmax = 3.272 MeV), and 214Pb (βmax = 1.022 MeV) beta decay particles.
