1-hr interior medical gas room

[Sifu]

IBC 427.2.2 requires the interior gas room to be separated from the rest of the structure by 1-hr fire barriers or horizontal assemblies. IBC 707.5 requires the fire barrier to extend to the underside of the roof sheathing, slab or deck above and be continuous through the concealed space (attic). The proposal is to provide fire barriers to the ceiling and terminate them in a horizontal assembly as a lid to the room. The proposal does separate the room, but the fire barriers do not terminate per 707.5. However 427.2.2 allows the use of a horizontal assembly to provide the separation.

The applicant has combustible roof framing and they would be inside the fire barrier separations if the fire barriers extended to the underside of the roof sheathing, which presents a problem. It seems like the use of fire barriers and horizontal assemblies to separate the spaces is specific to these gas rooms and the continuity of 707.5 wouldn't a apply, but maybe I am missing something. FYI I am requiring exhaust in a 1-hr shaft which can be routed between the combustible framing. Any thoughts are appreciated.

 

[mtlogcabin]

707.5 Continuity.
Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling. Joints and voids at intersections shall comply with Sections 707.8 and 707.9

Exceptions:

1. Shaft enclosures shall be permitted to terminate at a top enclosure complying with Section 713.12.

713.12 Enclosure at top.
A shaft enclosure that does not extend to the underside of the roof sheathing, deck or slab of the building shall be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.

 

[Sifu]

I read the same and considered it very much equivalent even though this is not a shaft. I am trying to figure out if there is a material difference that would require these particular fire barriers to go to the roof deck instead of terminating as a shaft or interior stair is allowed. Commentary points heavily to isolation to prevent gases from entering other parts of the building, but I think a fire barrier terminating at a horizontal assembly with a rated joint would do the same thing, plus I have the exhaust.

 

[mtlogcabin]

Where an exterior wall cannot be provided for the room, a 1-hour interior room or enclosure shall be provided and separated from the remainder of the building by fire barriers constructed in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711

711.2.4.6 Other separations.
Where a horizontal assembly is required by other sections of this code, the assembly shall have a fire-resistance rating of not less than that required by that section.

 

[klarenbeek]

How are they ventilating the room? IMC 502.9.1 requires mechanical ventilation of the room unless its on an outside wall. Both separate airstreams (exhaust and makeup air) are required to be shafted to the exterior, no fire dampers.

 

[Sifu]

Mechanical exhaust is provided directly to the roof termination above the room. I have required a 1-hr shaft.

 

[steveray]

IMO....If we are allowing exits to terminate at a lid, everything should be able to....

 

[Sifu]

I came to the same conclusions. Spoke with the architect and mechanical engineer yesterday and advised. Also reiterated the shaft requirement for the exhaust and outside air ducts. I think it is all good....for now.