In my opinion, you are right to be concerned about this design concept. As I’m 
sure you know, these detectors were intended to keep smoke from spreading 
between compartments during a fire by shutting down the HVAC fan units in the 
affected areas. Not as area smoke detection. Over the years I have developed a 
“distaste” for these units because of the many installation variations that I 
have seen that were not in conformance with the device listing or NFPA-72.  


To answer your question though, and this may not apply, at an Ohio correction 
facility that we worked on, there were “exhaust” ducts that came out of every 
cell and vented to the roof, that we put regular area smoke detectors into. It 
was a PITA to test them every year, but they did the job pretty well. I would 
be hesitant to use them as a detection for a pre-action system though. 


Ultimately, it’s your liability exposure that is the main concern here. In this 
configuration, depending on the CFM rating of the HVAC units, there could be a 
significant delay before a duct detector reaches alarm threshold. And I would 
make sure there were provisions for alarm verification or cross zoning 
protocols to prevent improper activation. 


Corrections is a tough market because the “tenants” have nothing to do all day 
but look for weaknesses in the infrastructure. 


My 2 cents worth.


John Paulsen – SET

Crown Fire System Design

6282 Seeds Rd.

Grove City, OH 43123

P – 614-782-2438

F – 614-782-2374

C – 614-348-8206




From: Sprinklerforum [] On 
Behalf Of michael G
Sent: Tuesday, September 20, 2016 11:15 AM
Subject: RE: Pre-action detection


No, they are back at the main return, that is it. just one duct detector, that 
covers about 30 cell pods.   They do not have any detectors in the grilles in 
the cell pods.   that’s our main concern.


From: Sprinklerforum [] On 
Behalf Of rongreenman .
Sent: Tuesday, September 20, 2016 11:07 AM
Subject: Re: Pre-action detection


I am presuming the duct detectors are just inside the return air from the cells 
and the day rooms  and other common areas are high ceilinged with normal 
detectors or where ceilings are low the access is limited.


On Tue, Sep 20, 2016 at 7:54 AM, < 
<> > wrote:

Where a fire alarm system is installed, duct detectors are an initiating device 
attached to and powered by the FACP system just as any other room detector.  
It’s essentially a regular detector head with tubes placed in an enclosure.  


Here’s a quote to chew on from the book, Operation of Fire Protection Systems:

“The detection of duct smoke is made difficult by its dilution with return air 
from other spaces (away from the fire) and possibly with outside fresh air.  
Also, when the HVAC system fan is not running, smoke may not reach the duct 
detector. For these reasons, air duct smoke detectors must never be considered 
as a substitute for open area protection.”





Craig L. Prahl 
Fire Protection Group Lead/SME
200 Verdae Blvd. 
Greenville, SC  29607
Direct - 864.920.7540 <tel:864.920.7540> 

Fax - 864.920.7129 <tel:864.920.7129> 

CH2MHILL Extension  77540 <> 


From: Sprinklerforum [ 
<> ] On Behalf Of Parsley 
Sent: Tuesday, September 20, 2016 10:22 AM
Subject: Re: Pre-action detection [EXTERNAL]


    The first issue that came to my mind was that the duct detector is 
frequently provided with power from the HVAC system and not from the FACU or 
releasing panel.  I don't know the logistics of what you're dealing with or 
whether that issue might have some impact however that might be worth looking 
into.  I have to admit I'd never heard of something like this.  That by itself 
doesn't mean it's outside the listing or the guidance in -72 or -13, just that 
I've never run across this configuration.

Ken Wagoner, SET
Parsley Consulting
350 West 9th Avenue, Suite 206
Escondido, California 92025
Phone 760-745-6181 <tel:760-745-6181> 
Visit our website <>  

On 09/20/2016 6:28 AM, Gregg Key wrote:



                              First of all, what a great convention. Good 
speakers and fellowship. Nashville was awesome as well. I am in serious need of 
some technical assistance. I have posted this a few times with some response 
but this has become a three ring circus between the architect ,fire marshal and 
us . The Architect specified a double interlock pre-action system with the 
detection being provided with a duct detector in the return duct at the unit. 
We have refused to certify the system due the fact that the detector not being 
listed for this application. State is asking me to hang a partial certification 
( yellow tag) . has anyone else dealt with this detection being used for a 
pre-action system in a detention center?   Any help would be appreciated  


Gregg Key

General Manager

Key Fire Protection Enterprises,LLC

3200 Mike Padgett Hwy

Augusta GA, 30906

O-706-790-3473 <tel:706-790-3473> 

C- 706-220-8821 <tel:706-220-8821> 

F- 706-738-2119 <tel:706-738-2119> <>  




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Ron Greenman

4110 Olson Dr., NW
Gig Harbor, WA 98335 <> 



The Universe is monstrously indifferent to the presence of man. -Werner Herzog, 
screenwriter, film director, author, actor and opera director (1942-)




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