# something different



## cda (Sep 21, 2010)

Clean agent system

1. air sampling system with sampling tubes at the ceiling and about half way down the room, same spacing for both.

2. smoke detectors at about the half way point down from the ceiling, mounted on large opening metal grid rail.

sequence is

a. two smokes set of system

or

b. one smoke, and air sampling alert, sets off system

anyone seen the smokes mounted more then a foot down and accepted it???


----------



## globe trekker (Sep 21, 2010)

cda,

No, I have never seen the "smokes" located down on the wall.   They have

always been ceiling mounted.

Is this "Clean Agent System" an all encompassing, "designed" system, or

is it "piece mealed" together?

.


----------



## cda (Sep 21, 2010)

Highly designed

It was a note on the building plans but not on the fire alarm plans submitted


----------



## TimNY (Sep 21, 2010)

I believe there are criteria for detectors located below the ceiling in an atrium situation.  It's been a white, but I think it's in 72 somewhere.  maybe the appendix?  What kind of space is this?


----------



## cda (Sep 21, 2010)

four different rooms of various electrical equipment


----------



## TJacobs (Sep 21, 2010)

Since the smokes are not for occupant notification in a residential setting, I would say it is an engineering decision...


----------



## Dr. J (Sep 22, 2010)

Assuming the clean agent system is an initial response system only, and any required automatic fire suppression system is a water based sprinkler system, then the layout and operation is, to a large extent, up to the designer.  Perhaps due to high air exchange rates needed for cooling, the designer feels that the normal smoke banking at the ceiling does not apply, and a more spread out detection sytem is needed.

I would also assume that any smoke detector still sets off occupant notification, so the ASSD at the ceiling meet the code requirement for that purpose.  The other smoke detectors are bonus.


----------



## cda (Sep 22, 2010)

D J

No sprinklers

Do not think air movement comes into play

It takes at least one smoke to trip the system

We have asked for some testing or other from a smart person, or move the smokes to the deck


----------



## Dr. J (Sep 22, 2010)

Can the ASSD at the ceiling be considered the NFPA 72 compliant system, with all the others being bonus?

Per NFPA 72:  _5.7.3.3.1  Each sampling port of an air sampling–type smoke detector shall be treated as a spot-type detector for the purpose of location and spacing._

Just look at the ceiling, ignore everything below.


----------



## FM William Burns (Sep 22, 2010)

Provided the rooms are below the humidity, transport time and within the temperature thresholds; I would be inclined to agree with Dr J and believe that the ASSD is used as the ceiling initiation and the banked spots are redundant volume "failsafe" initiation means, all dependant on ceiling and predicted airflow and exchange rates. 

Ask for and review the flow characteristics for the ASSD and make sure it has supervisory means to warn when the airflow is below the range of the detector.


----------



## cda (Sep 22, 2010)

But they want to cross zone so it takes two devices to dump the system

If they go to the air sampling only, then it seems more likely to dump, when only requiring one device????

I can live with one system to dump the system, not sure if the owner would


----------



## globe trekker (Sep 23, 2010)

These "clean agent systems" have a very expensive suppression agent in their design.

It's probably time to have a sit down meeting with the designer and discuss your

concerns!

Let us know how it turns out!

.


----------



## cda (Sep 23, 2010)

We threw it back to them either take smokes to deck or provide documentation for review that shows testing or other that someone has put thier name to.


----------



## FyrBldgGuy (Sep 23, 2010)

Only guessing, but if they are designing for different types of smoke plumes based upon the materials present and the need to respond quickly, then it might be a very specific performance system.  Otherwise it is probably just a bad designer.


----------

