If a pipe must be carried through a wood partition, protection for the woodwork can be provided by cutting an opening in the partition and inserting a galvanized-iron double-wall ventilating shield at least 12 inches larger than the pipe (fig. 13) or by using at least 4 inches of brickwork or other incombustible material. Smoke pipes should never pass through floors, closets, or concealed spaces or enter a chimney in a garret. Gases formed by burning the sulfur contained in coal are the main cause of corrosion of metal smoke pipes. Little corrosion occurs during the heating season, when the pipe is kept hot and dry. The life of metal pipes can be prolonged if each summer when they are not in use they are taken down, cleaned, wrapped in paper, and stored in a dry place. This is especially true of pipe to heaters in damp cellars. [Illustration: Figure 13.--_A_, Elevation of protection around a stovepipe passing through a frame partition; _B_, sectional view.] [Illustration: Figure 14.--Method of insulating wood floor joists and baseboard at a chimney with 4-inch walls. A single header is used as it is less than 4 feet long.] _Insulation_ No wood should be in contact with a chimney. Leave a space of 2 inches between the outside face of a chimney and all wooden beams or joists except when 8 inches of masonry is used outside flue lining, in which case the framing may be within one-half inch of the chimney masonry. The space between the floor framing and the chimney may be filled with porous, nonmetallic, incombustible material, such as loose cinders. Brickwork, mortar, and concrete are not suitable. Place the filling before the floor is laid, as it not only forms a fire stop but prevents accumulation of shavings or other combustible material. Subflooring may be laid within one-half inch of the masonry. Baseboards, when fastened to plaster that is directly in contact with the wall of a chimney, can be protected by a layer of fireproof material, such as asbestos, at least one-eighth of an inch thick between the woodwork and the plaster (fig. 14). Wooden studding, furring, or lathing should not be placed against a chimney but set back, as indicated in figure 9; or the plaster may be applied directly to the masonry or to metal lath laid over the masonry. The former is the better method, as settlement will not crack the plaster. It is recommended that a coat of cement plaster be applied directly upon the outside surfaces of masonry chimneys that are to be incased by a wooden partition or other combustible construction. Metal lath, lapped 6 inches on the masonry, at the intersection of chimneys with partitions prevents corner cracks. (See plan in fig. 34.) _Chimney and Roof Connection_ Where the chimney passes through the roof, provide a 2-inch clearance between the wood framing and masonry for fire protection and for expansion due to temperature changes, settlement, or slight movement of the chimney during heavy winds.