Radon-222 is a natural decay product of the uranium-radium series which exists everywhere on earth and significantly contributes to the environmental radioactivity. It is a rare gas which is colourless, odourless, and tasteless, does not combine and escapes from the soil via cracks and gaps into breathable air. Further decay results in radioactive decay products which get into the lung via respiratory ducts, where they emit, among others, alpha radiation. This can damage the lung’s cells. These damages can influence the risk of contracting cancer.