Presented techniques and research results relating to the gas-bearing capacity and gas and dynamic features of the Third potash level seam rocks at the different sections of mine fields of the potash mines of the First, Second and Third Production Units of «PA «Belaruskali». Given the quantitative evaluation of the rocks gas-bearing capacity of the 4th sylvinite stratum and clay and carnallite package of the Third potash level relating to the free and inflammable gases. The received results are designated to be used while engineering and perfecting the mining systems and modes of potash mines ventilating.