A sealing system for a flow tube keeps cement from getting around it to the flapper when the safety valve is in the open position. The fixing device is removably installable in the image forming apparatus and includes a rotary fixing member to fuse a toner image on a recording medium, a fixing frame to support the fixing member, and an outer fixing cover provided to cover the fixing member and the fixing frame and having an opening from which a portion of a surface of the fixing member is exposed to the outside. USE: Ski boots and skating boots, safety footwear and the like.