717.5.4.1 Corridors - offspring to R-1 corridor wall penetration thread

[rgrace]

I started looking the cda's post, and agreed with how confusing Chapter 7 can be at times, so I thought I would point out what confuses me about 2018 IBC Section 717.5.4.1 Corridors.

1- The is a subsection to 717.5.4 Fire partitions.
2- Duct and air transfer openings the penetrate fire partitions shall be protected with a listed fire damper.
3- There are 4 exceptions to this including one for a corridor. Follow exception 1, fire damper not required.

4- 717.5.4.1 Corridors
5- Duct and transfer openings that penetrate corridors shall be protected with dampers. Okay, not well defined, but we can still move forward.

6- Number 1 says a corridor damper shall be provided blah, blah, blah. Yea, this one throws me off. What is a corridor damper? It's not defined in the IMC. Is it a smoke damper? Fire damper? Radiation damper? The IBC has a definition that simply calls it a "listed device." Blah, blah, blah goes on to say that this "corridor damper" is required where corridor ceilings are constructed as required for the corridor walls per 708.4 exception 3. Doesn't that make the corridor ceiling a fire partition? If don't fire partitions require a fire damper at a duct penetration? Why not say fire damper instead of corridor damper?

7- Number 2 says a ceiling radiation dampers shall be provided blah, blah, blah. Ahh, a defined term. However the rest is confusing. Blah, blah, blah goes on to say this this is applicable to floor-ceiling and roof-ceiling assemblies per 708.4 exception 2. Looks to me that 708.4 exception 2 is not specific to floor-ceiling and roof-ceiling assemblies. As a matter of fact, it doesn't even make mention of these assemblies, only of the lower membrane of a corridor ceiling (which as shown above could be a fire partition) and the corridor wall membrane (which is a fire partition). So, this tells me that Number 2 is only applicable where a floor-ceiling or roof-ceiling is included in the corridor dasign. For those other designs, I suppose it's a corridor damper?

8- Number 3 says a smoke damper shall be provided (no blah, blah, blah this time) in duct penetrations of corridors that are required to have smoke and draft control doors only. Aren't Group I-2 and I-3 the only places where this could be applicable? If so then the two exceptions here would only apply to corridor conditions in Group I-2 and I-3, not in any R condition.

Feedback is welcome, clarification is encouraged. Perhaps next time we can discuss shaft options for Groups I-2 and I-3 under Section 717.6.1?

 

[Sifu]

Revival of this: I know it's old, and it's Friday, but figured I would give it a shot in case anyone gets bored with the beer and bratwurst over the extended weekend.

717.5.4 requires a fire damper in fire partitions, unless by exception.
717.5.4.1 requires a smoke damper in corridor walls at ducts and transfer openings when a corridor is required to have smoke and draft control doors per 716.2.2.1. In the post above Q.#8 questioned where that occurs, proposing it is only in I-2 and I-3. Reading 716.2.2.1 it appears that any door assembly in t716.1(2) would be subject to this. The table includes "fire partitions: corridor walls". Wouldn't then, the requirement apply to any rated corridor door?

To expand on 717.5.4.1:
Base code requires a SD in a corridor wall assuming the doors are subject to smoke and draft control, then exception #2 excepts the smoke damper in the corridor wall if the duct is steel and there are no openings serving the corridor. My question is if the corridor is served by 2 different systems.

My current project: R2, VB, NFPA 13R, 3 story, 2018 IBC. The corridor has an unrated lid with an outdoor air system and a supply air system between the unrated lid and the rated floor assembly above it. The OA system is dedicated and has no openings other than steel ducts directly to each unit. There is a FD at each OA system penetration of the corridor/unit wall. The SA comes directly from an FCU with it's own OA and supplies only the corridor via ceiling registers in the unrated lid. There is a return air path in the space above the unrated lid (plenum) but the FCU has smoke detection that shuts the system down.

The FD on the OA system would be required per 717.5.4 base code (assume exceptions don't apply).
The SD on the corridor/unit walls would be required as well unless 717.5.4.1 #3 unless exc. 1) I am wrong that this corridor is subject to 716.2.2.1 or 2) the duct is steel and there are no openings serving the corridor. My question about this exception is the "no openings serving the corridor" part. There are no openings from the OA serving the corridor, but there are openings from the SA serving the corridor, both supply and return. Both systems share the same space. If we read it literally, then the exception would not apply. This makes some sense to me since if there were smoke from a unit, it could travel unrestricted to the corridor plenum through a FD that has not closed, and into the corridor below via the unrated lid and/or open return air. However, since the OA system is closed, the only smoke from the unit would not communicate with the plenum space, it would only fill up the OA system, which is closed. If the exception intends that only the system that is penetrating the corridor/unit wall and that it communicates with the corridor then the exception would apply and no SD required.

Am I wrong about the corridor being subject to 716.2.2.1?
Am I wrong about the idea that the exception would only be negated if there is a communicating opening?

Pasting some pertinent commentary:
717.5.4


717.5.4.1