# Smoke Detectors for Atrium Smoke Control



## hbendillo (Apr 10, 2014)

I am working on a project to replace an existing smoke detection system for an atrium.  The old smoke evacuation system is completely inadequate and everything, including the controls have to be replaced.  I am working with a mechanical engineer who is designing the new system.  My part of the project is to make sure the fire alarm system is designed properly to activate the system and to design circuits from the existing emergency power system to power the equipment.

I have been researching the codes, copying code sections and highlighting related requirements.  The existing atrium is a three-story space adjoining an existing high-rise office building.  Basically it is an atrium stuck on to the side of the existing 34-story building.  The atrium has existing beam type smoke detectors below the atrium roof protecting the open atrium space.  The three floors projecting into the atrium space from the high rise have ceiling mounted smoke detectors installed around the perimeter of the atrium.  I need to make sure the smoke detectors around the perimeter are spaced properly and located properly in relation to the edge of the atrium.  Is the standard 30' spacing acceptable?  Do they need to be within 15' of the edge of the atrium perimeter or closer?

It has been a very long time since I have done one of these.  Any suggestions on where to look would be appreciated.  I have looked through NFPA-92, International Building Code (Sections 404, 907 and 909) and NFPA-72.  I thought there was more specific information about the spot detectors used for atrium smoke control but haven't found anything.  Thanks.

I know this is a pretty simplistic explanation of a complex system but if anybody has any comments I would appreciate it.


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## cda (Apr 10, 2014)

so why not go back with what you have?  Just update the technology

suggest work with a fire protection engineer

72 will just give you spacing per the type of detector

The other thing has anyone sat down with the ahj and see what they want/need???


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## hbendillo (Apr 10, 2014)

cda said:
			
		

> so why not go back with what you have?  Just update the technologysuggest work with a fire protection engineer
> 
> 72 will just give you spacing per the type of detector
> 
> The other thing has anyone sat down with the ahj and see what they want/need???


The AHJ is the federal government, GSA, and we have a pretty clear idea of what they want.  The fire alarm technology can be updated easily enough to adapt to our new design.  I am at the beginning of my research for what I have to do.  I have done many fire alarm  systems in my time for many different applications.  I just want to make sure I have all the information I need to modify the existing system and update for this specific application.  It has probably been 20 years since I did an atrium smoke control system.  I am pretty sure that the smoke detector spacing does not need to be less than is required normally for a required automatic detection system.  I somehow have stuck in my mind that the distance from the edge atrium perimeter to the detectors from the adjoining floors is three feet. Thanks.


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## cda (Apr 10, 2014)

in 72 2010 edition there is 17.6.3.5

covers up to 30 feet

and spacing off a wall should be half the required spacing.


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## FM William Burns (Apr 10, 2014)

You may want to look at the Special Considerations Section for high air movement areas since openings into a 3 story atrium will probably meet this criteria and the velocity could effect spacing and location.


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