Smoke Partition Ceilings for Corridors

[100eyeballs]

In regards to I-2 occupancy, ICC 2009 requires corridors to be non-rated, 711 Smoke Partitions. While normally these partitions are built to the underside of deck above, there are cases where this is problematic. The 711.4 Continuity subsections allows the partition to stop at the underside of the ceiling above where the ceiling membrane is constructed to limit the transfer of smoke. The code is afterward silent about the acceptance of suspended ceiling tile "to limit the transfer of smoke". Sometimes in looking at the requirements of 712.3.1 for fire-resistance rated horizontal assemblies, we can say that the ceiling tile should be 1 lb/foot to prevent uplift pressure, but this really is a stretch since there is no language that ties the two together. There would be no UL test to prove a suspended ceiling would "limit the transfer of smoke", since there's no requirements to test for, such as limiting by a percentage or cubic feet of air per minute, etc. It seems like a bed sheet would limit the transfer of smoke and meet this requirement.

Of course in I-2 occupancies the NFPA 101 usually applies, so we can look at 18.3.6.2 for the Construction of Corridor Walls in hospitals. Here the language is the same: to limit the transfer of smoke. There is appendix material that states: An architectural, exposed, suspended-grid acoustical tile ceiling with penetrating items is capable of limiting the transfer of smoke.

There is an interesting paper online from the State of Louisiana where they've ruled in favor of suspended ceilings in absence of a national standard: http://sfm.dps.louisiana.gov/doc/interpmemos/im_2006-05.pdf

So the question is, can we definitively say suspended ceilings are allowed in corridors of I-2 buildings in lieu of smoke partitions that extend to the deck above to meet the continuity requirement? Is there any other documentation out there from ICC or other evaluation services that would shed light on the subject?

 

[RLGA]

You can find the NIST report mentioned in the Louisiana document here: http://fire.nist.gov/bfrlpubs/fire82/PDF/f82011.pdf

The NIST report, as well as the Louisiana document, states that a suspended ceiling prevents downflow of smoke when an "interstial space exhaust" is used. The Louisiana document does not include this as a condition of approval, which makes it suspect in my opinion.

I have difficulty in accepting that suspended ceilings alone (even with the conditions mentioned in the Louisiana document) will effectively "limit the transfer of smoke," as required in the 2009 IBC. However, the requirement is to "limit" and not "prevent." So the requirement is open to a variety of interpretations, since there is no objective performance criteria provided in the code like there is for doors.

 

[100eyeballs]

Exactly. How can we say suspended ceilings aren't effective at "limiting" when we don't know how much they are suppose to limit - either in volume, percentage, or otherwise. I have seen this argument used to gain approval in some hospitals, and while not a typical recommended approach, I am trying to gather around the right facts to cement a position for acceptance in the cases where it is the only practical approach. Thanks for the link to the NIST report. Any other helpful documentation would be appreciated.

 

[JustReid]

Further reference is in NFPA 101 A.8.4.2(2). It is essentially the same wording for the Chapter 18 reference above. The handbook commentary goes on to say this,

"A smoke partition should be thought of as a barrier that reasonably limits, but does not necessarily prevent,

smoke transfer. As such, there are suspendedceiling systems and monolithic surfaced ceilings that provide resistance to smoke transfer that is approximately equal to that of the traditional, nonrated corridor wall or partition. Smoke partitions are permitted to terminate tightly against the underside of such ceilings in accordance with 8.4.2(2). The concept is further described in A.8.4.2(2). The list of acceptable penetrating items (e.g., speakers, recessed light fixtures, and ducted HVAC air diffusers) makes it clear that a smoke partition is not intended to prevent all smoke transfer; rather, it limits the transfer of smoke to an acceptable level to provide for occupant life safety."

 

[100eyeballs]

Does anyone know of further ICC interpretations or supporting documentation on 711 Smoke Partitions? I need to support the same case that NFPA makes with using only ICC. Is that possible?

 

[cda]

code allows you to reference other standards/codes and also shoot an alternative materials and methods

 

[Codegeek]

I found this in the 2009 IBC Commentary...

The continuity provisions for smoke partitions are similar to those for fire partitions (see Section 709.4), except that the issue is smoke spread, not fire. Therefore, the allowance for termination at the underside of the ceiling membrane (as opposed to the underside of the floor or roof deck above) relates to the ability of the ceiling membrane to limit the spread of smoke. Typical “lay in” ceiling tiles, for instance, would probably not serve this function; however, a drywall ceiling that is taped and finished would be an example of construction that could resist the passage of smoke.

 

[100eyeballs]

Yes, thanks. I have seen this unfortunate language in the ICC commentary that says lay in ceiling would probably "NOT" serve this function. This flies in the face of pages of NFPA commentary that says the opposite. One of the crucial hinge points in ICC is the work "Limit". Where NFPA clearly defines limit to mean "reduce", others interpret it to be "totally stop". This doesn't make sense when you look at the amount of smoke allowed to go through a door opening - 3 cubic feet per minute per square foot. That's 63 cubic feet per minute for a 3'x7' door.

So is ICC and NFPA really at odds with each other on the topic of Smoke Partitions? Or is this one ICC commentary an anomaly?

 

[Codegeek]

This wouldn't be the first time that ICC and NFPA conflict!

Seriously, it has always my understanding that the smoke partition was to limit (or reduce) the passage of smoke, not necessarily stop it.