Outlets for exhaust that exceed 600°F (315°C) shall be designed as a chimney in accordance with Table 18-28-511.2.
The termination point for exhaust ducts discharging to the atmosphere shall not be less than the following:
1. Ducts conveying explosive or flammable vapors, fumes or dusts: 30 feet (9144 mm) from property line; 10 feet (3048 mm) from openings into the building; 6 feet (1829 mm) from exterior walls or roofs; 30 feet (9144 mm) from combustible walls or openings into the building which are in the direction of the exhaust discharge; and 10 feet (3048 mm) above adjoining grade.
2. Other product-conveying outlets: 10 feet (3048 mm) from property line; 3 feet (914 mm) from exterior wall or roof; 10 feet (3048 mm) from openings into the building; and 10 feet (3048 mm) above adjoining grade.
3. Environmental air duct exhaust: 3 feet (914 mm) from property line; and 3 feet (914 mm) from openings into the building.
Chimneys Serving | Minimum Thickness | Termination | Clearance | |||||||
Wall | Lining | Above Roof Opening (Feet) | Above Any Part of Building Within (Feet) | Combustible Construction (Inches) | Noncombustible Construction | |||||
10 | 25 | 50 | Interior Inst. | Exterior Inst. | Interior Inst. | Exterior Inst. | ||||
Low-heat appliances (1,000°F normal operation) | 0.127" (No. 10 MSG) | None | 3 | 2 | – | – | 18 | 6 | Up to 18" diameter, 2" Over 18" diameter, 4" | |
Medium-heat appliances (2,000°F maximum) | 0.127" (No. 10 MSG) | Up to 18" dia. - 2 1/2" Over 18" - 4 1/2" on 4 1/2 bed | 10 | – | 10 | – | 36 | 24 | ||
High-heat appliances (over 2,000°F) a | 0.127" (No. 10 MSG) | 4 1/2" laid on 4 1/2 bed | 20 | – | – | 20 | See Footnote C | |||
For SI: 1 inch = 25.4 inch, 1 foot = 304.8 mm,°C =[(°F)-32]1.8.
a. Lining shall extend from bottom to top of outlet.
b. Lining shall extend from 24 inches below connector to 24 feet above.
c. Clearance shall be as specified by the design engineer and shall have sufficient clearance from buildings and structures to avoid overheating combustible materials (maximum 160°F).