<p>A numerical simulation of the ignition of an ultralean (equivalence ratio of the mixture is 0.1) hydrogen–air mixture at pressures of 1 and 5 atm in the temperature range of 910–1600 K was performed using several detailed kinetic mechanisms. A comparison was made of the experimentally recorded profiles of the electron-excited OH^* radical with the calculated ones. At normal pressure (1 atm), the experimental results agree well with the results of calculations based on the mechanisms of Tereza et al. and Konnov (2019), and at elevated pressure (5 atm) with the results of FFCM-2, Konnov 2019, and Tereza et al. A comparative analysis of the experimentally measured ignition delay with the results of numerical simulation demonstrated the best agreement for calculations based on the mechanisms of Tereza et al. and Konnov (2019).</p>