Arrangement for reducing harmful effects from fire and/or explosion comprising wall elements that are placed in adjacent relationship to one another to form a continuous wall. The element are adapted, when an explosion occurs, to open the area towards the surroundings until the pressure in the area is balanced in relation to the surroundings. Thereafter the elements return to their closed state to enclose the area in relation to the surroundings, preventing air from the surroundings from entering the enclosed area and prevent fire extinguishing fluids from exiting the enclosed area. Preferably, the elements comprises an elastically deformable material so that when the element is forced open, elastic energy is stored in the element to rapidly return the element to the closed state.