A safety device is disclosed which is configured to be actuated by the supply of gas. The safety device incorporates an outlet vent pipe which is sealed by a releasable clip. The releasable clip has a first elongate main gripping element and a second elongate moveable gripping element. The main gripping element has a retaining element to retain one end of the moveable gripping element. The safety device also includes an arrangement to retain the other end of the moveable gripping element in a predetermined position such that the clip may grip a fabric tube or the like between the main gripping element and the moveable gripping element. A mechanism is provided which responds to a supply signal to move the other end of the moveable gripping element to release the grip.