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June 20, 2010

                             []< ET NEWS                               
====================================================================== 
    NEWS AND INFORMATION FOR THE FIRE PROTECTION ENGINEERING TEAM      
---------------------------------------------------------------------- 
 Issue No. 424  ISSN 1554-074X      http://www.etnews.org   6-20-2010  
====================================================================== 
 
Contents
--------
- News
- Journal
- Employment
- Seminar Schedule
- Comments & Acknowledgements 
 
====================================================================== 
NEWS
====================================================================== 
 
Job of the day: Fire alarm technician Pinellas
MyFox Tampa Bay
Eligibility Requirements: To be eligible for participation in the 
project (for hire for position), the applicant's total family income 
must be at or less ... 
http://www.myfoxtampabay.com/dpp/jobs/daily_jobs/job-of-the-day-fire-
alarm-technician-060310 
 
---------------------------------------------------------------------- 
 
US Fire Administration  
Today's training vignette, "Combination Smoke and Fire Damper 
Actuators" explains the requirements for these devices.  
http://www.usfa.dhs.gov/downloads/pdf/coffee-break/cb_fp_2010_25.pdf 
 
---------------------------------------------------------------------- 
 
NFPA Announces Theme for Fire Prevention Week 2010
Fire Department Network News
The National Fire Protection Association (NFPA) has announced the 
theme for this year's Fire Prevention Week: Smoke Alarms: A sound you 
can live with. ... 
http://fdnntv.com/NFPA-theme-Fire-Prevention-Week-2010 
 
---------------------------------------------------------------------- 
 
This week I'll see you in Rochester. 
 
We're rolling out live webinars in August.   More info to come ...
 
- Mike 
 
Twitter -> http://www.twitter.com/codeweenie 
 
Blog -> http://codeweenie.blogspot.com/ 
 
====================================================================== 
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====================================================================== 
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====================================================================== 
ET NEWS JOURNAL                                                        
====================================================================== 
 
LOCATION AND SPACING OF SMOKE DETECTORS IN HIGH CEILING APPPLICATIONS 
---------------------------------------------------------------------

QUESTION 
-------- 
I'm sure this comes up a lot.

How do you determine Spacing reduction on ceiling mounted smoke 
detectors for high ceilings? 

I have a project with 20' Flat ceilings.  We used the listed spacing 
of 30'.  Should we have reduced the spacing? 

Chris G.
Tyler, TX 

ANSWER 
------ 
 
Hello Chris,

We discuss this in my Intermediate and Advanced Fire Alarm seminars.  
It's easier in person but I'll give it a shot via email message.

Smoke detector spacing isn't reduced as a function of ceiling height 
like heat detectors are but rather additional smoke detectors may be 
required because of ceiling height.  The reference is:

NFPA 72-2010 17.7.1.10* The effect of stratification below the ceiling
shall be taken into account. The guidelines in Annex B shall be 
permitted to be used.

The reference in Annex B is:
 
FIGURE B.4.6.3.2.2 Temperature Change and Maximum Height of Smoke Rise 
for Given Fire Sizes.

The Annex B graph plots stratification as a function of fire size and 
delta T (the difference in temperature between floor and ceiling).  
The fire size is plotted as a curve, depending on fire size.  Delta T 
is the y axis and stratification height in the x axis.  

The concern is that if fire size is too small and or delta T is too 
large and or the ceiling is too high then stratification will occur, 
which will prevent the fire plume from rising to the ceiling to form a 
ceiling jet and therefore intersect with a smoke detector.  

Here's an example; Since the concern is small fire, assume the 
smallest fire size plotted, which is 100 Btu/sec (trash can filled 
with milk cartons).  The concern is also regarding a large delta T so 
assume a large delta T, such as 100 degrees F.  In other words, if 
it's 75F at the floor then it's 175F at the ceiling.  Look at where 
the small fire plot intersects the y axis at 100F and then extend that 
point down to the x axis where you'll find that smoke will stratify at 
25 ft above the floor.  Therefore, if your ceiling is 25 feet or less 
above the finished floor, then stratification is of no concern even 
considering a very small fire (100 Btu/sec) and very large delta T 
(100F).  If your ceiling height is more than 25 feet, you've just 
revealed a problem.  Annex A offers some suggestions regarding the 
problem.  The reference in Annex A is:

A.17.7.1.10 Stratification of air in a room can hinder air containing 
smoke particles or gaseous combustion products from reaching ceiling-
mounted smoke detectors or fire-gas detectors.

Stratification occurs when air containing smoke particles or gaseous 
combustion products is heated by smoldering or burning material and, 
becoming less dense than the surrounding cooler air, rises until it 
reaches a level at which there is no longer a difference in 
temperature between it and the surrounding air.

Stratification also can occur when evaporative coolers are used, 
because moisture introduced by these devices can condense on smoke, 
causing it to fall toward the floor. Therefore, to ensure rapid 
response, it might be necessary to install smoke detectors on 
sidewalls or at locations below the ceiling.

In installations where detection of smoldering or small fires is 
desired and where the possibility of stratification exists, 
consideration should be given to mounting a portion of the detectors 
below the ceiling. In high-ceiling areas, projected beam-type or air 
sampling-type detectors at different levels also should be considered. 
(See Figure A.17.7.1.10.) 
 
FIGURE A.17.7.1.10 Smoke Detector Layout Accounting for Stratification. 
 
- Mike 
 
This response should not be considered a formal interpretation but 
rather the author's opinion. 
  
====================================================================== 
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====================================================================== 
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====================================================================== 
JOB OPPORTUNITIES
====================================================================== 
 
JOB OPPORTUNITY and SEEKING EMPLOYMENT announcements are provided as a 
service.  ET News provides a venue for direct contact between job 
seekers and employers.  ET News is not a placement agency and does not 
endorse either job seekers or employers. 
 
---------------------------------------------------------------------- 
 
Post your announcement at http://www.etnews.org/index.php?s=257
 
====================================================================== 
SEMINAR SCHEDULE
====================================================================== 
 
Contact me regarding seminar sponsorship mailto:mikebaker@afaa.org 
  
------------------
June 22-24, 2010 Rochester NY 
------------------ 
Basic Fire Alarm 
Intermediate Fire Alarm (NICET I & II) 
Sponsored seminars (closed)  
 
------------------ 
August 3-5, 2010 Maitland FL 
------------------ 
Fire Alarm System Testing and Inspection 
Intermediate Fire Alarm (NICET I & II) 
http://www.afaa.org/pdf/TI_IntFA_Orlando_Aug2010.pdf 
 
------------------ 
August 31 and September 1-3, 2010 Kent WA 
------------------ 
Fire Alarm System Testing and Inspection 
Understanding IBC-2009 Fire Alarm Requirements 
Intermediate Fire Alarm (NICET I & II) 
http://www.afaa.org/pdf/TI_IBC_IntFA_Kent_Aug2010.pdf 
 
------------------ 
September 7-9, 2010 Phoenix AZ 
------------------ 
Fire Alarm System Testing and Inspection 
Intermediate Fire Alarm (NICET I & II) 
http://www.afaa.org/pdf/TI_IntFA_Phoenix_Sep2010.pdf 
  
====================================================================== 
COMMENTS AND ACKNOWLEDGEMENTS 
====================================================================== 
 
ET News is written nearly every week and almost always sent on Sunday. 
 
Doug Hockinson built ETNews.org using PHP/MySQL-> http://www.phpvs.com 
 
---------------------------------------------------------------------- 
Some information may be found in this message and etnews.org that is   
reprinted with permission from one or more of the following; NFPA 70   
National Electrical Code(r), NFPA 72(r) National Fire Alarm Code(r),   
NFPA 101(r) Life Safety Code(r), Copyright(c) NFPA, Quincy, MA 02269   
This reprinted material is not the complete and official position of   
the NFPA on the referenced subject, which is represented only by the   
standard in its entirety.                                              
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This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety.