This standard specifies a method for the determination of the free radon exhalation rate of a batch of mineral based building materials. The standard only refers to 222Rn exhalation determination using two test methods: Liquid Scintillation Counting (LSC) and gamma ray spectrometry (Annex A and Annex B)The exhalation of thoron (220Rn) does not affect the test result when applying the determination methods described in this part of the standard.