Undercut doors in dormitory

[acb324]

In a dormitory, can the dorm rooms be under negative pressure relative to the corridor? Does this create a potential issue if a fire started in one of the dorm rooms, as far smoke pouring out into the egress corridor?

As far as I can tell, NFPA 101 chapter 28 on dormitories prohibits transoms, louvers, or transfer grilles, but does not speak to the air transfer through the undercut of a door.

NFPA 80 allows up to 3/4" of undercut on a fire rated door.

My confusion really arises from NFPA 90A. 4.3.12.1.3.2 regarding egress corridors states that where door clearances do not exceed those specified for fire doors in NFPA 80, air transfer caused by pressure differentials shall be permitted. However, immediately after that 4.3.12.2 states that exit passageways shall not be used as a part of a supply, return, or exhaust system serving other areas of the building. It seems to me that an egress corridor is an exit passageway, and so these two things directly contradict one another. Any clarification on the intent here would be helpful. Thank you.

 

[acb324]

Sorry, I just reread that and I stated it backwards. The corridor would be negative compared to the dorms.

 

[cdafd]

Is this a general question or a new building or existing building question???


From IBC;;,

Two different animals

EXIT PASSAGEWAY. An exit component that is separated from other interior spaces of a building or structure by fire-resistance-rated construction and opening protectives, and provides for a protected path of egress travel in a horizontal direction to the exit discharge or the public way


1023.3 Construction. Exit passageway enclosures shall have walls, floors and ceilings of not less than 1-hour fire-resistance rating, and not less than that required for any connecting exit enclosure. Exit passageways shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 712, or both.

1023.5 Openings and penetrations. Exit passageway opening protectives shall be in accordance with the requirements of Section 715.

Except as permitted in Section 402.4.6, openings in exit passageways other than exterior openings shall be limited to those necessary for exit access to the exit passageway from normally occupied spaces and for egress from the exit passageway.

Where an exit enclosure is extended to an exit discharge or a public way by an exit passageway, the exit passageway shall also comply with Section 1022.2.1.

Elevators shall not open into an exit passageway.

And:

CORRIDOR. An enclosed exit access component that defines and provides a path of egress travel to an exit.

http://www.vonduprin.com/fireandlifesafety/Fire_and_Life_Safety_Code.pdf

http://idighardware.com/?s=Undercut&submit=

 

[acb324]

This is new construction. IBC is not adopted, but NFPA is. My concern is whether or not nfpa speaks to the pressure differential being acceptable.

 

[cdafd]

You might post your question here

http://idighardware.com/about-2/get-more-hardware-help/

Or here

http://www.thebuildingcodeforum.com/forum/commercial-building-codes/

 

[cdafd]

""""NFPA 90A. 4.3.12.1.3.2 regarding egress corridors states that where door clearances do not exceed those specified for fire doors in NFPA 80, air transfer caused by pressure differentials shall be permitted"""

I think this will be the answer to your question, because you are dealing with a corridor and not an exit passageway

 

[acb324]

Thanks cdafd. I got concerned looking at the nfpa glossary of terms where the definition of exit passageway was "Hallways, corridors, passages, or tunnels used as exit components and separated from other parts of the building in accordance with NFPA 101®, Life Safety Code®." It seemed to me as though the two sections I listed from nfpa 90a were conflicting.

 

[cry22]

International Mechanical code section 602.1 states the definition of a plenum which is limited to uninhabited spaces such as attic, mech rooms, above ceiling space, undefloor space.

IMC 601.2 Air Movement in Egress Elements - Corridors shall not be used as supply, return, exhaust relief or ventilation air ducts

To me, if your HVAC system provides positive pressure in the Hallway with door undercuts, undercut or not - you should pass, meaning that you dorm will ex-filtrate the excess air through cracks in the windows or into the plenum if any.

Looks like corridor in negative in a no-go per IMC

 

[acb324]

Just to close the loop here:

I called NFPA for technical clarification and the specialist said per 90A this was ok. He confirmed that this approach, while not the norm, is perfectly acceptable. You can transfer air from the sleeping quarters through the undercut door and exhaust it through the egress corridor. He added that the thought process is that by the time the smoke in that room reaches the floor to transfer out into the corridor, that occupant would be dead or evacuated (hopefully the latter!).

I thought for a moment the design got caught up by an excerpt from the local building code high rise section, but that section was exempt when fully sprinklered.