NFPA 72 does not define “Area Coverage”.

However, they do define partial or selective coverage.
From NFPA 72, 2016 Handbook* Partial or Selective Coverage.   Where other governing laws, codes, 
or standards require the protection of selected areas only, the specified areas 
shall be protected in accordance with this Code.

A.    If there are no detectors in the room or area of fire origin, the 
fire could exceed the design objectives before being detected by remotely 
located detectors. When coverage other than total coverage is required, partial 
coverage can be provided in common areas and work spaces such as corridors, 
lobbies, storage rooms, equipment rooms, and other tenantless spaces. The 
intent of selective coverage is to address a specific hazard only.
Where a specific area is to be protected, all points within that area should be 
within 0.7 × the adjusted detector spacing for spot-type detectors as required 
 Note that an area does not necessarily mean an entire room. It is possible to 
provide properly spaced detectors to provide detection for only part of a room. 
Similarly, the Code permits protection of a specific hazard. In that case, 
detectors within a radius of 0.7 × the adjusted detector spacing from the 
hazard provide the required detection. An example of protection of specific 
risk is the smoke detector required by Section 
21.3<> to 
be within 21 ft (6.4 m) of an elevator, where elevator recall is required.
It should also be noted that fire detection by itself is not fire protection. 
Also, protection goals could be such that detection being provided for a 
specific area or hazard might require a form of total coverage for that 
particular area or hazard. That is, it might be necessary to provide detectors 
above suspended ceilings or in small closets and other ancillary spaces that 
are a part of, or an exposure to, the area or hazard being protected.

72 also doesn’t mention anything about being Listed “FOR AREA PROTECTION”. 
However, it does mention against using duct detectors as substitutes for open 
area coverage.*    Detectors placed in environmental air ducts or plenums shall not 
(Emphasis by me) be used as a substitute for open area detectors. Where 
detectors are used for the control of smoke spread, the requirements of 
 shall apply. Where open area protection is required, 
 shall apply.
In most buildings, there are periods when the HVAC system is not moving 
significant quantities of air from the compartments it serves. As a result, the 
fire detection system cannot be designed to rely on the HVAC system operation 
for the transport of smoke to smoke detectors.

A.    Smoke might not be drawn into the duct or plenums when the 
ventilating system is shut down. Furthermore, when the ventilating system is 
operating, the detector(s) can be less responsive to a fire condition in the 
room of fire origin due to dilution by clean air.

They both point out smoke dilution and delayed activation.

Kind Regards,


Mike Henke CET
Sprinkler Product Manager


Potter Electric Signal Company, LLC
1609 Park 370 Place, St. Louis, MO 63042
phone: 800-325-3936   |   direct: 314-595-6740<>   |<>

From: Sprinklerforum [] On 
Behalf Of
Sent: Tuesday, September 20, 2016 10:43 AM
Subject: RE: Pre-action detection

Define “Area Coverage”.  The duct detector covers or senses within the same 
AREA the air handling system serves.

Does it say in either NFPA 13 or NFPA 72 that a detector has to be listed “FOR 
AREA PROTECTION”?  Actually a detector isn’t really protecting anything, just 
sensing and alarming.

Craig L. Prahl
Fire Protection Group Lead/SME
200 Verdae Blvd.
Greenville, SC  29607
Direct - 864.920.7540
Fax - 864.920.7129
CH2MHILL Extension  77540<>

From: Sprinklerforum [] On 
Behalf Of michael G
Sent: Tuesday, September 20, 2016 11:16 AM
Subject: RE: Pre-action detection [EXTERNAL]


They don’t make a Duct detector that is listed for area of protection.   Also 
our other major concern.

Michael Goodis
Estimator, Project Manager
IL#000635   NICET#135586
Key Fire Protection Enterprises LLC
3200 Mike Padgett HWY
Augusta, GA 30906
Office- (706)790-3473
Cell- (706) 220-8822
Fax: (706) 738-2119

From: Sprinklerforum [] On 
Behalf Of Bruce Verhei
Sent: Tuesday, September 20, 2016 11:01 AM
Subject: Re: Pre-action detection

Guess I'll be the angel's advocate. Is the duct detector listed for area 

That said, I think (51%) that a detector in the exhaust from each one-person 
cell was used as the detection for such a system in Kent WA. I was not the plan 
reviewer for this project so I am not sure.

Operator is King Co. Constructed as King County Regional Justice Center, 
renamed Norm Maleng Regional Justice Center. I don't have a current contact.


Bruce Verhei

On Sep 20, 2016, at 07:04, <<>> 
<<>> wrote:
Playing devil’s advocate here for a minute, how does the duct detector differ 
from a room detector with regards to its listing for this application?

How does a duct detector sensing room smoke conditions differ from a VESDA 
system which samples air from a room?

Does the HVAC unit serve only the same area as the preaction system covers?

Is there specific verbiage cited within NFPA 13 or NFPA 72 which does not allow 
the use of an HVAC return air smoke detector as an initiating device for a 
preaction system?

Craig L. Prahl
Fire Protection Group Lead/SME
200 Verdae Blvd.
Greenville, SC  29607
Direct - 864.920.7540
Fax - 864.920.7129
CH2MHILL Extension  77540<>

From: Sprinklerforum [] On 
Behalf Of Gregg Key
Sent: Tuesday, September 20, 2016 9:28 AM
Subject: Pre-action detection [EXTERNAL]


                              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
C- 706-220-8821
F- 706-738-2119<>

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