Abstract <p>The ability of some samples of coal enrichment waste to adsorb oxygen is investigated. The incubation period of self-ignition (spontaneous combustion) is determined, as well as the likelihood of self-ignition of coal-bearing rock. Some of the samples are susceptible to spontaneous combustion and their presence in tailings heaps may result in endogenous fires. Self-ignition of coal slurry is unusual because of its high moisture content. However, laboratory research shows that slurry may rapidly lose moisture in summer, and the incubation period is significantly shortened. That may lead ultimately to spontaneous combustion hot spots. To prevent endogenous fires, the incubation period must be determined for coal enrichment waste in rock tailings.</p>