This paper demonstrates experimental and numerical study on spontaneous ignition of H2-N2 mixtures during high-pressure release into the air through the tubes of various diameters and lengths. The mixtures included 5%2and 10%2(vol.) N2 addition to hydrogen being at initial pressure in range of 4.3 - 15.9 MPa. As a point of reference pure hydrogen release experiments were performed with use of the same experimental stand and extension tubes. The results showed that N2 addition may increase the initial pressure necessary to self-ignite the mixture as much as 2.08 or 2.85 - times for 5%2and 10%2N2 addition respectively. Additionally, simulations were performed with use of Cantera code (0-D) based on the ideal shock tube assumption and with the modified KIVA3V code (2-D) to establish the main factors responsible for ignition and sustained combustion during the release.