Coal continues to be the major source of energy and various subsidiaries of Coal India Limited serve as prominent coal producers towards generation of electricity. Operational safety is a major concern as considerable danger of fire looms due to spontaneous combustion of such power coals in the process of storage and transportation. In total, sixty-six (66) coal samples obtained from various subsidiaries of Coal India such as ECL, BCCL, CCL, WCL, NCL, SECL and SCCL have been investigated to assess their inclination towards auto oxidation leading to spontaneous combustion. For this, a convenient method has been utilized comprising tubular reactors that works on the intrinsic nature of coal and is based on the guidelines of DGMS. It has been observed that on an average the coal samples from BCCL are least prone to auto oxidation, which lead to spontaneous fire, whereas the samples from SECL are most prone. Based on the average data, the proneness follows the order: SECL > ECL > NCL > CCL > WCL > SCCL > BCCL. The auto oxidation phenomenon has been correlated with the composition of coal which suggests that oxygen bearing groups play a significant role. According to the reflectance studies, it is quite evident that lower rank coals are more prone to spontaneous fire.