This paper is aimed at investigation of the spontaneous ignition process of high-pressure hydrogen and hydrogen-methane mixtures injected into the air. The experiments were conducted in a closed channel filled with air where the hydrogen or hydrogen-methane mixture was injected through different geometries (various diameters and extension tube lengths). The methane addition to the mixture was 5%2and 10%2[v/v]. The results showed that only 5%2methane addition may 2.75 times increase the pressure at which the mixture may ignite in comparison to the pressure of the pure hydrogen flow. The 10%2of methane addition did not provide an ignition for burst pressures up to 15.0 MPa in the geometrical configuration with the longest tube (100 mm). Additionally, the simulations of the experimental configuration with pure hydrogen were performed with the use of KIVA numerical code with full kinetic reaction mechanism.