The invention relates to an autonomously functioning ignition system which, with a simple design, allows reliable ignition of combustible gas mixtures already slightly above the ignition limit. According to the invention, this is achieved by an ignition system (2) for igniting combustible gas mixtures, particularly in a containment structure (4) of a nuclear facility, comprising an electric ignition element (24) and a thermoelectric generator (8) as a source of current for said ignition element (24).