I once went down a rabbit hole of the required rating of exit fire separations…what I found is a bit of discrepancy between Part 9 and Part 3. Let me explain:

The common and accepted application is that the exit separation is based solely on the 3.2.2. requirement and does not consider higher ratings required by major occupancy or storage/repair garages. This is stated in Sentence 3.4.4.1.(1):

I do agree the Code is pretty clear in Part 3 that only 3.2.2. is to be applied (although I don’t necessarily agree that this is right), however Clause 9.9.4.2.(1)(a) does not reference Table 9.10.8. for protection of structural members (however, Clause 9.9.4.2.(1)(b) does.). Table 9.10.8. gives us some of the information that we would fine in the 3.2.2. classification if the building was Part 3.  This is stated in Sentence 9.9.4.2.(1):

Now for an example, which highlights the discrepancy:

1. A Part 9, 599 m² two storey building. First storey commercial repair garage (F2) and second storey is one (giant) residential suite (C). Floor is required 2 h per Article 9.10.9.17. Per 9.9.4.2., the exit at the first storey is required to be 2 h, but 45 min at the second level.
2. A Part 3, 602 m² two storey building (3.2.2.76.). First storey commercial repair garage (F2) and second storey in one (giant) residential suite (C). Floor is required 2 h per 3.3.5.6., but exit at first storey only 45 min per 3.4.4.4.(1). An additional vestibule is not required per 3.3.5.4.(1) as it is not a storage garage, it is a repair garage.

These are virtually the same building. Scenario 1 requires a 2 h exit separation at the first storey (Part 9), and Scenario 2 requires a 45 min exit separation at the first storey (Part 3). How curious. 

This requires a lot of coordination, and I have found it is not well understood (for how I interpret the Code anyways).

On top of fire separation requirements in Section 3.1., an exit fire separation has additional restrictions to ensure service penetrations do not adversely affect the integrity of the exit. This means, that what may be okay for a typical fire separation, is not good enough for an exit fire separation. These additional requirements are found in Article 3.4.4.4., and apply to the exit stair, as well as any exit corridor which connects an exit stair to the exterior.

Sentence 3.4.4.4.(1) states:

You will notice that ductwork is not a permitted penetration in an exit separation. Even if the duct has a fire and/or smoke damper, it is not permitted by Code. There is a reference in Part 6 in regards to ducts in exits, however I assume this is an oversight. If you have thoughts on ducts in exits, please share them in the Community Q & A here. Yes – I posted the question myself. And, no – no one has answered. Don’t leave me hanging!

How I read the above is that if something is not listed in (a) through (e), it better not be penetrating the exit separation. It seems straightforward to read, but I have found applying this to be a nightmare.

Something to note is that I have not spend much time in the field, and most of my Code work has been on the plan review side. So, it took me a while to realize that exit walls are penetrated all the time, as partial penetrations. See the image below for what I mean by a partial penetration. Essentially, the outer membrane of the exit fire separation is penetrated, but not the inner membrane.

If I’m to read the Code and apply it how I believe it was intended, partial penetrations would not be permitted. A fire separation is a system, and to me the outer membrane is a part of that system and is also required to follow Sentence 3.4.4.4.(1). I understand that it is easier during construction to allow partial penetrations, but it seems to me like this is a design and a habit issue, as opposed to a Code issue.

If I had any confidence that walls did not end up looking like swiss cheese over time and penetrations were always fire-stopped appropriately I might not be as concerned…but I have a few too many Fire Inspector friends who deal with buildings long after the initial work is done to be okay with the status quo.

From my experience, it depends on the AHJ how partial penetrations are interpreted and enforced. When interpretation is an issue, I highly recommend check with the AHJ early on as it can affect system designs.

There is a BC Building Code Interpretation that seems to address partial penetrations and notes that they are okay in the outer membrane. A reminder that interpretations are not legally binding and an AHJ may still disagree with them. There is also a Community Q & A regarding partial penetrations which could use your insight!

The only slight relaxation for exit requirements is when an exit is permitted to lead through a lobby… which I have seen applied very loosely in many instances.

The word ‘lobby’ is where I think most of the confusion stems from. The lobby still needs to provide a high level of protection, and should not contain an occupancy. There are actually only a few relaxations permitted, which are:

• Spaces other than residential, care, industrial, or service rooms can open onto the lobby,
• The fire separation between the lobby and a room for direct supervision does not require a fire-resistance rating,
• The fire separation between the lobby and adjacent occupancies does not require a fire-resistance rating if the building is sprinklered, and
• Passenger elevators can open onto the lobby.

You will also notice that ductwork is not a relaxation for an exit though lobbies, however I am often told that it is ‘standard practice and acceptable’. If the Code did permit duct penetrations, I would imagine the Code would also require smoke dampers at those locations, which it does not (see Sentence 3.1.8.7.(2))…. some food for thought. If you have some thoughts on this, please share them in the Community Q & A here. Yes – I am the only only who has shared thoughts…please join me in the discussion!

If you are super keen, check out the NRC Users Guide pages 84/85 for additional information. It’s quite interesting to read, as how we perceive lobbies today seem to greatly vary from the way the relaxation was initially intended.

You can also check out the CFSA Newsletter (Page 15) which discusses Toronto’s approach to lobbies containing combustible materials.

If you like solving Code riddles, this one is tons of fun! Sentence 3.1.8.3.(3) has requirements for exit enclosure shafts and states:

Because of how it is worded with ‘shaft penetrating a roof assembly’ listed first, most people don’t read on and see that this is also applicable to exit enclosures.

I find this comes into play often when you have exit corridors, or an exit stair that is at the center of the building and has a horizontal extension to the outside of the building. This also applies when there is an attic space above the exit shaft. How I read the Code is that in either scenario, the vertical walls of the exit (enclosure/corridor or shaft) are required to be carried up to the underside of the floor or roof. I have run into countless designs where there is a service space above that has not considered this requirement.