ɹˈeɪdɑːn tˈuːhˈʌndɹɪd twˈɛnti tˈuː ˌɑːɹɹˈɛn ɹᵻlˈiːst ˌɪntʊ ðɪ ˈɛɹ dᵻkˈeɪz tə tˈuːhˈʌndɹɪd tˈɛn pˌiːbˈiː ænd ˈʌðɚ ɹˌeɪdɪoʊˈaɪsətˌoʊps ænd ðə lˈɛvəlz ʌv tˈuːhˈʌndɹɪd tˈɛn pˌiːbˈiː kæn biː mˈɛʒɚd.
Radon (222Rn) released into the air decays to 210Pb and other radioisotopes and the levels of 210Pb can be measured.