§ 23.20.601.4. Contamination prevention.

Amend by adding the following two exceptions:

Exceptions:

* * *

3.

Environmental air exhaust ducts under positive pressure may extend into or through ducts or plenums if one of the following design approaches is used:

a.

Route environmental air exhaust ducts inside a shaft when passing through a duct or plenum.

b.

Install a second duct around the environmental air exhaust duct where passing through ducts and plenums to minimize leakage to the duct or plenum; seal both ends of the outer duct to outside.

c.

Seal the environmental air exhaust ducts along all seams and joints using a listed low to medium pressure duct sealant, typically applied by brush, trowel, or caulking gun; install sealant per manufacturer's recommendations.

d.

Provide flexible duct with no seams in the duct or plenum only to a limit of eight (8) feet. The eight (8) feet limit is due to high static losses. Also, sleeving the metal duct with flexible seamless duct is acceptable.

4.

Gas vents installed in accordance with section 503.3.6 in the International Fuel Gas Code.

( AO No. 2015-127, § 1, 4-1-16 )