Tornados can damage collections in many ways. Books and papers may be blown from shelving and desks. Collections may be scattered, damaged and soiled. Roofs may blow off and walls and buildings may collapse, burying collections under dirt, beams, furniture and yard debris, or leaving collections exposed and vulnerable to wind, rain and snow. Structural collapse may cause fire damage to collections due to broken gas and power lines, as well as water damage from fire hoses and sprinklers, or broken water or sewer pipes. Collections may be recovered from damage if appropriate measures are taken. Dry collections may be salvaged and cleaned of soil, wet collections may be frozen to prevent mold growth, and broken book bindings, photographs and papers can be boxed or treated by professional conservators.