Goal. Metal frame supports SVP-22 with round timber lagging and backfilling of the voidsof unsupported space with chock support is used in the workings of unstable ores and rocks at the Orlovsky mine. When filling the voids with a chock supportmanually, people are located in an unsupported part of the working, therefore this operation is hazardous and laborious. The purpose of the work is to select and test the backfill material for voids of unsupported space, which ensures a decrease in diffusion and oxygen seepage to the centers of spontaneous ignition of the ore bodies under conditions of intense oxidation of sulphide ores at the Orlovsky deposit. Methods. Foaming non-combustible materials (“Blockfil” phenolic two-component resins) were tested in the experimental works at the Orlovsky mine for backfilling the voids when supporting the mine workings by metal frame supports with a round timber lagging. Results. It has been established that the use of phenolic resins as backfilling will reduce the intensity of the oxidation reaction and prevent self-heating of the ore to critical temperatures, and also prevent or slow down the process of heating ofmine air from the heated surface of the ore body to temperatures exceeding the design values. Conclusions. The use of phenolic resin “Blockfil” to fill the voids ensured the absence of deformation of the elements of the metal frame support and the safety of mining, and also allowed to reduce the intensity of the oxidation reaction and prevent self-heating from the ore to critical temperatures and prevent or slow down the process of heating the mine air from the heated surface of the ore body to temperatures, exceeding the design values.