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Transite originated as a brand that Johns-Manville created in 1929 for a line of asbestos-cement products, including boards and pipes. In time it became a generic term for other companies' similar asbestos-cement products, and later an even more generic term for a hard, fireproof composite material, fibre cement boards, typically used in wall construction and can be found in insulation, siding, roof gutters, and cement wallboard.
The use of asbestos to manufacture transite was phased out in the 1980s. Previously transite was made of cement, with varying amounts (12-50%) of asbestos fiber to provide tensile strength (similar to the steel in reinforced concrete), and other materials. It was frequently used for such purposes as furnace flues, roof shingles, siding, soffit and fascia panels, and wallboard for areas where fire retardancy is particularly important. It was also used in walk-in coolers made in large supermarkets in the 1960s, 1970s and even the 1980s. Other uses included roof drain piping, water piping, sanitary sewer drain piping, laboratory fume hood panels, ceiling tiles, landscape edging, and HVAC ducts. Because cutting, breaking, and machining asbestos-containing transite releases carcinogenic asbestos fibers into the air, its use has fallen out of favor. Despite asbestos-containing transite being phased out, it is still not banned in the United States and has been attributed to 230,000 deaths. Demolition of older buildings containing transite materials, particularly siding made from transite requires special precautions and disposal techniques to protect workers and the public. Finding and safely handling asbestos-containing transite is dangerous and difficult and should only be done by an asbestos abatement professional.
The transite that is produced today is made without asbestos. Transite HT and Transite 1000 are currently available fiber cement boards that contain no asbestos. Instead they contain crystalline silica, which the International Agency for Research on Cancer has classified as being carcinogenic to humans (Class 1). Crystalline silica is also known to cause silicosis, a non-cancerous lung disease.
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