(1)
Return-air systems shall comply with Article 3.6.5.8.
(2)
Where a ceiling space is used as a return-air plenum, the requirements of Article 3.6.4.3. shall apply.
(3)
A public corridor or exit shall not be used as a return-air plenum.
(4)
The return-air system shall be designed to handle the entire air supply.
(5)
The return-air system shall be designed so that the negative pressure from the circulating fan cannot affect the furnace combustion air supply nor draw combustion products from joints or openings in the furnace or flue pipe.
(6)
Return-air inlets shall not be installed in an enclosed room or crawl space that provides combustion air to a fuel-fired appliance.