In underground coal mines, the methane distribution under actual conditions has a certain concentration gradient due to various factors such as air leakage and lower air velocity in local areas. In this paper, experiments were carried out to investigate the influence of the methane accumulation and concentration gradient on the methane–air explosion propagation. The experimental results show that in the process of methane explosion, the propagation distance of the flame and explosion wave in the rising stage are directly proportional to the methane accumulation. When the reaction time is less than a critical value, the flame propagation velocity and explosion overpressure with methane concentration distribution in the case of 9.5%–9.5%–3.5% are greater than those with a methane concentration change of 9.5%–9.5%–5.5%. However, when the methane concentration distribution is 9.5%–9.5%–0%, the flame propagation velocity and overpressure are less than those of the distributed methane in the working conditions of 9.5%–9.5%–3.5% and 9.5%–9.5%–5.5%.

Air-doors are important facilities for regulating the air flow in a mine ventilation network. It is of value to study the influence of air-doors, which are adjacent to a fire source on smoke back-layering in order to build a rational ventilation system. By regulating air-doors in a mine ventilation network test platform, two typical mine ventilation networks, with parallel branches and a diagonal branch, were constructed. During the study, into the closing degree of the air-doors adjacent to a fire source in a ventilation network with parallel branches, the back-layering length is up to 3.70 m when the ventilation velocity is 1.40 m/s. When the air-door on the return side of the adjacent branch is closed, the back-layering subsides within 1 min and the upstream temperature drops rapidly to normal. When the air-door is half closed, there is still a back-layering flow within 5 min. Smoke control, with the air-door is closed, is better than when the air-door is half closed. Based on this, tests into the influence of the closing position of air-doors, which are adjacent to a fire source, were carried out in a ventilation network with a diagonal branch. Results indicate that when the ventilation velocity is 1.70 m/s, the back-layering flow spreads to the diagonal branch, and the air flow velocity of both the adjacent branch and the diagonal branch increases. When closing the air-door on the return side of the adjacent branch, the back-layering rapidly subsided. The wind velocity on the intake side of the adjacent branch is stabilized after a rapid decrease, and the wind velocity of the diagonal branch is stabilized after a rapid increase. When closing the air-door on the intake side of the adjacent branch, the smoke from the diagonal branch spreads. Compared with closing the intake side air-door, closing the air-door on the return side of the adjacent branch is more effective in preventing back-layering. This work provides a reference for preventing back-layering and guiding the evacuation of people from the upstream of a fire source.