I recently ran into s similar situation in a large mechanical room. Large duct 
within 4" of a pair of W sections that went horizontally about 60 ft. The 
pocket above was impossible to get to and provide little protection is 
activated. We put sprinklers under the duct and at either end at roof level. 
Omitted sprinklers above. This was accepted by the AHJ and FM Global. It is 
always best to run this by them first.

Todd G Williams, PE Fire Protection Design/Consulting Stonington, CT 
860-535-2080 (ofc) 860-608-4559 (cell)
Sent using CloudMagic 
On Thu, Sep 15, 2016 at 6:46 AM, tcfire <tcf...@bellsouth.net> wrote:
I say no since it sounds like you have a total compartmetalization of the 
hallway with the dry wall partitions extending vertically to the deck.
In this situation heads above the duct would be useless.

Sent from my Sprint Samsung Galaxy S7.
-------- Original message -------- From: Tim Stone <tston...@comcast.net> Date: 
9/14/16 10:04 PM (GMT-05:00) To: sprinklerforum@lists.firesprinkler.org 
Subject: Noncombustible concealed space
I have an interesting situation.

Steel and concrete School building. A Corridor runs down the middle on each 
floor about 8’ wide, W12 steel I-Beams forming the side at the floor deck 
above, (About 12’-0 Floor to Bottom of deck).

There is a large duct running the length of the Corridor about 7’-6 wide x 24” 
tall. This leaves a gap of about 3” on each side between duct and sheetrock 
partitions. The top of the duct is about 11” below the steel Q-Deck above.

An open metal grid ceiling system is installed 12” – 16” below the duct.

We are installing upright heads 1”-4” below the duct allowing the water to 
spray down through the open grid ceiling.

The question is, do I need to install heads above the duct? There will be no 
way to service or replace these heads and if installed between the duct and the 
wall, the head will not meet the minimum 4” off the wall.

Referencing 2010 ed., concealed spaces, I believe I am following the 

Thank you in advance.


G. Tim Stone

G. Tim Stone Consulting, LLC

NICET Level III Engineering Technician

Fire Protection Sprinkler Design

and Consulting Services

117 Old Stage Rd. - Essex Jct., VT. 05452

CELL: (802) 373-0638 TEL: (802) 434-2968 Fax: (802) 434-4343

tston...@comcast.net [tston...@comcast.net]
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