Figure 3. Tracks of alpha particles emitted by radon in a CR-39 detector. One viewing field from the microscope has the area of about 0.53 mm2

From

Measurement of Radon Exhalation Rate from Destroyed Building Material in the Gaza Strip

M.O. El-Ghossain

International Journal of Physics. 2016, 4(6), 146-151 doi:10.12691/ijp-4-6-1