In this paper, the reactive properties of coals associated to the low temperature oxidation were studied by using Thermogravimetric analysis (TGA). Coal samples were pulverized into a size fraction <106µm and analysed using two non-isothermal thermogravimetric methods. The ‘adsorption of oxygen’ test consisted of exposing coal samples to slow heating rates in air whilst measuring the weight increase produced by the oxygen adsorption. Two heating ramps were used (3 and 5oC min-1) recording the net mass increases from 20 to 250oC. Results range from 0.0% up to 4.4% weight gain, with the lowest heating rate giving the highest levels of adsorption. A second thermogravimetric test for spontaneous combustion potential (TGspc) was developed which focussed on the linear segment of the weight derivative curve between 150 and 350oC at different ramp rates in air (3, 5, 7, 10 and 20oC min-1). From these results, a relationship between the mass loss rate and temperature was obtained (TGspc index), where high values were produced by highly reactive coals. The ‘oxygen adsorption’ test related to the chemisorption step, which precedes ‘spontaneous combustion’. The ‘TGspc’ test was more related to the combustion process, post-ignition. These results also agreed with the known behaviour for the samples studied, indicating that these tests could be useful tools to identify coals prone to self-oxidation.