Laboratory tests have been undertaken to study the temperature dependence of radon (Rn) concentration in coal. The tests are of fundamental importance in relating the intensity of a subsurface coal heating with its surface Rn concentration anomaly. A specially designed experimental apparatus was built to undertake the tests. The results of the tests show that the Rn concentration increases significantly with coal temperature. As temperature was raised from 30 degrees C to 180 degrees C, the Rn concentration in coal increased by 8 to 10 times, indicating that the Rn concentration and the intensity of the coal heating are closely related. Even within a low temperature range (between 30 degrees C and 70 degrees C) the Rn concentration also increased substantially, by 2 to 3 times, implying that Rn concentration in coal may be used as a precursor for early detection of a coal heating. (C) 2010 Elsevier B.V. All rights reserved.