This paper is an investigation of the spontaneous ignition process of high-pressure hydrogen and hydrogen-methane mixtures injected into air. The experiments were conducted in a closed channel filled with air where the hydrogen or hydrogen methane mixture depressurised through different tubes (diameters d = 6, 10, and 14 mm, and lengths L = 10, 25, 40, 50, 75 and 100 mm). The methane addition to the mixture was 5% and 10% vol. The results showed that only 5% methane addition may increase even 2.67 times the pressure at which the mixture may ignite in comparison to the pressure of the pure hydrogen flow. The 10% of 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. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.