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APPLICATION
Grease Ducts
Double wall grease ducts are listed for a continuous internal temperature of 500°F and intermittent
temperatures of 2000°F. Double wall grease duct is ideally suited for use in commercial cooking
installations for the removal of smoke and grease laden vapors. Grease duct system size and capacity
information may be obtained from the ASHRAE Handbook – Fundamentals or from the Air Pollution
Engineering Manual of the US Environmental Protection Agency. Grease duct installations require
provisions for cleaning the interior of the duct. NFPA 96 clean-out requirements are as follows:
1. A clean-out must be provided at each change of direction, except where the entire length of duct can
be inspected and cleaned from either the hood or the discharge end.
2. On horizontal duct runs, at least one 20” diameter opening must be provided. Where the opening is
smaller than 20” diameter, openings large enough to permit cleaning must be provided at intervals of
no more than 12’.
3. Openings must be at the side or the top, whichever is more accessible. When the opening is on the
side of the duct, the lower edge of the opening must be at least 1-1/2” above the bottom of the duct.
For the listed grease duct, this is accomplished by the use of the grease manifold tee and clean-out
cap.
4. On vertical duct runs where personnel entry is possible, access must be from the top of the riser.
Where entry is not possible, access must be provided at each floor.
NOTE: Access requirements are subject to change in accordance with local code. Local authorities
should be consulted for exact requirements. Grease duct may be connected only to hoods in a
single fire zone on one floor. Do not connect grease ducts to any other part of the building
ventilation or exhaust system.
When the grease duct is installed in accordance with these installation instructions and the joints are
sealed properly with the recommended sealant, the system will contain a fire within the duct. A fire can
burn at extremely high temperatures. The system should be dismantled and inspected after any exposure
to a fire. Any section that is distorted or discolored should be replaced. All joints in the system should be
examined.
The sealant expands to ensure a positive seal in the case of a fire, and any sealant that has been exposed
to high temperature must be replaced. This will ensure that the system maintains its integrity against fire
conditions in the future. The manufacturer of this grease duct cannot be responsible for grease duct
systems that are not properly maintained or have been subjected to one or more fire conditions.
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