High altitude is characterised by hypoxic and hypobaric conditions. Exposure to high altitude is known to affect human physiology, specially blood oxygen tension and saturation. Also, oxygen, carbon dioxide and vacuum are known to affect some polymers used in radon detection. In the present work alpha track detector (CR–39 plastic) was used to assess the radon exhalation rates and effective radium in rock, soil, plants (wild herbs) and water samples measured at low altitude with normal oxygen and atmospheric pressure and compared with the corresponding measurements in hypoxic and hypobaric conditions at high altitude (2412 m above sea level). The data indicated that high–altitude conditions slightly affect the measurements of the radon concentration and its exhalation rate.