NFPA 82-1999 Standard on Incinerators and Waste and Linen Handling Systems and Equipment.
2-2.9 Chimney Clearances. 2-2.9.1 Listed chimneys shall be installed in accordance with the conditions of the manufacturer’s instructions for clearances. Exposed portions of chimneys or breechings that can be touched shall be so designed that maximum surface temperatures shall not exceed 70°F (39°C) above ambient temperature. 2-2.9.2 Masonry Chimneys. A clearance of not less than 4 in. (102 mm) shall be provided between the exterior surface of masonry chimneys and combustible material. 2-2.9.3 Exterior Metal Chimneys. 2-18.104.22.168 Exterior metal chimneys shall have a clearance of not less than 24 in. (610 mm) from a wall of wood frame construction and from any combustible material. 2-22.214.171.124 Exterior metal chimneys over 18 in. (457 mm) in diam- eter shall have a clearance of not less than 4 in. (102 mm), and those chimneys 18 in. (457 mm) or less in diameter shall have a clearance of not less than 2 in. (51 mm) from a building wall of other than wood frame construction. 2-126.96.36.199 An exterior metal chimney shall be installed with a min- imum clearance of 24 in. (610 mm) to any door or window or to any walkway, unless insulated or shielded in an approved manner to prevent a person from coming in contact with the chimney.
2-2.12 Chimney Connector or Breeching. 2-2.12.1 A chimney connector or breeching connecting a com- mercial-institutional-type incinerator to a chimney shall be con- structed of not lighter than 16 U.S. gauge steel if it is 12 in. (305 mm) or less in diameter or greatest cross-section dimension, and of not lighter than 12 U.S. gauge steel if it exceeds 12 in. (305 mm) in diameter or greatest cross-section dimension. Exception: Breechings that utilize listed medium-heat chimney sections, provided these sections are joined together with continuous welds, flanges, or couplings. 2-2.12.2 Chimney connectors or breeching up to 18 in. (457 mm) in diameter or greatest cross-section dimension shall be lined with not less than 2 1 / 2 -in. (63.5-mm) high-duty, spall-resistant refrac- tory brick (as defined in ASTM C 27). 2-2.12.3 Chimney connectors or breeching over 18 in. (457 mm) in diameter or greatest cross-section dimension shall be lined with not less than 4 1 / 2 -in. (114-mm) of high-duty, spall-resistant refractory brick (as defined in ASTM C 27).NFPA 82 pdf download.