Following the accident at the Fukushima Daiichi nuclear power plant, combustible gas behaviour and related accident management measures have been the subject of increased study and analysis. This has included on measures to limit the fission product release into the environment. This publication reviews the current state of technology regarding combustible gas related safety issues in water cooled nuclear reactors, with a specific focus on post-Fukushima Daiichi accident developments. The recent results obtained from experimental and analytical research on hydrogen/combustible gas behavior are discussed. The knowledge base developed will be useful for validation and assessment activities related to combustible gas modelling implemented in the existing safety analysis tools. It may also contribute to future improvements in severe accident management guidelines.