Safety distances for hydrogen plumes are currently derived using models developed for hydrocarbon releases. It is well known that hydrogen behaves in a significantly different manner to that of hydrocarbons when released to atmosphere. There are two main aspects involved with the development of safety distances for credible hydrogen releases; the intensity of the thermal radiation from such a plume should it be ignited, and the distance downwind from the release point to the point where a flammable mixture with air no longer exists. A number of distinct areas of venting behaviour were investigated; Thermal radiation from ignited plumes from vertical open ended vent pipes Far field radiation measurements for direct comparison with models Thermal radiation from ignited plumes from vertical vent pipes terminating in a T-piece Thermal radiation measurements from ignited hydrogen with a 45 vent termination Hydrogen concentration measurements with a T-piece.