The presence of a return air plenum doesn't automatically necessitate sprinklers. Sprinklers are going to be required in the space if combustibles with ratings equal to or above that which is allowed for a concealed space are present as defined in NFPA 13.
If it is a plenum it may actually be beneficial from a fire protection standpoint in that the utilities within that plenum have to be specifically rated for such use, thus minimizing their risk for fire and smoke spread. This may result in no need for sprinklers in the plenum space. You could put in 2x2 or 4x4 free return (without ductwork) grilles into the ceiling for that matter and it wouldn't change the combustible nature of the space above the ceiling. Also the HVAC units will or should have smoke detection to sense any smoke present from the return air. Unit smoke detection of course will depend on the size of the air handlers. Craig L. Prahl, CET Fire Protection Group Mechanical Department CH2MHILL Lockwood Greene 1500 International Drive PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 [EMAIL PROTECTED] http://www.ch2m.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Fletcher, Ron Sent: Tuesday, August 05, 2008 9:59 AM To: [email protected] Subject: RE: Floating Ceilings You can have an unlimited number 2'x4' return air grills in the ceiling without adding sprinklers above but put a 4" wide slot around edge of the room and sprinklers are required. Go figure. Where do you get "a plenum thus requiring sprinklers"? Ron Fletcher Aero Automatic Sprinkler Phoenix, AZ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Maag, Barry Sent: Tuesday, August 05, 2008 6:08 AM To: [email protected] Subject: RE: Floating Ceilings I have seen these types in the past and the "space" around the floating ceiling was used for the return air for HVAC. This made the area above the ceiling a plenum thus requiring sprinklers -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Green Sent: Tuesday, August 05, 2008 7:59 AM To: [email protected] Subject: Floating Ceilings I am in the design phase installing wet pipe sprinkler systems protecting new schools. I have noticed that in several of the rooms in the schools(cafeteria, band room, main corridor that runs the length of the school), architect has designed lay-in ceiling systems with gaps ranging from 4" to 12" along the walls and between sections of ceiling within the rooms (floating ceiling sections). I do not believe my non-combustible concealed space above the ceilings is concealed anymore and may require protection. Has anyone dealt with this? I have heard some discussion that if the total square feet of the openings is below a certain percent of the total square foot of a space, sprinkler protection above the space may not be required? Interesting thing is that the school is being built as a "Green" project and seems like the designed openings would make the schools less energy efficient. Anyone's help would be most appreciated... Rick E. Green District Manager East Coast Fire Protection, Inc. 1113 Cavalier Boulevard Chesapeake, Virginia 23323 757/485-7486(p), 757/295-0956(direct), 757/328-0131(cell) [EMAIL PROTECTED] _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
