International Mechanical Code Section 510.8 is hereby amended to read as follows:

510.8 Suppression required. Duct shall be protected with an approved automatic fire suppression system installed in accordance with the International Building Code.

Exceptions:

1. An approved automatic fire suppression system shall not be required in ducts conveying materials, fumes, mists and vapors that are nonflammable and noncombustible under all conditions and at any concentrations.

2. Automatic fire suppression systems shall not be required in metallic and noncombustible, nonmetallic exhaust ducts in semiconductor fabrication facilities.

3. An approved automatic fire suppression system shall not be required in ducts where the largest cross-sectional diameter or width of the duct is less than 10 inches (254 mm).

4. For laboratories, as defined in Section 510.1, automatic fire protection systems shall not be required in laboratory hoods or exhaust systems.