In this investigation, ignition processes of the methane and the propane using a high-temperature oxidizer .T oxi > T ai / with a varying oxygen concentration z O2 -the HTAC (High Temperature Air Combustion) conditions, applying a constant-volume bomb (CVB) was investigated. The influence of the initial temperature of the oxidizer T oxi was analyzed and discussed. It is shown that in order to achieve an effective reaction of ignition the oxidizer temperature needn't be maximized. Detailed evolution of ignition delay time with equivalence ratio ig was presented. It can be concluded that increment of oxygen concentration z O2 in oxidizer results in decrease of ig . Trials with propane are characterizing lower values of ignition delay time ig in comparison with methane.