Abstract: A Jet Catcher, which is a device for dissipating the energy of a gaseous jet flow, comprises a base member and a plurality of porous screens mounted on the base member. The screens are so mounted that when the Jet Catcher is in use with an axis of the catcher parallel to the direction of flow of the jet the angles of the screens to the direction of flow of the undisturbed jet decrease in the downstream direction. The base member is preferably of combined conical/frustoconical or combined pyramidal/frusto-pyramidal form with the apex being, in use, the most upstream point of the base member.