How to Properly Sprinkler a Vertical Shaft?

8/20/2021

I'm laying out the fire sprinklers for a building where the architect has used the IBC exception in Section 403.2.1.2 that requires sprinklers to be installed at the top and alternating floor levels of a vertical shaft. This reduces the required shaft enclosure to be 1-hour for highrises up to 420 feet.

NFPA 13 doesn't seem to address this specific arrangement. I've looked and I'm not finding any installation requirements. I have concerns with just putting sprinklers in the shaft.

What's the best type of sprinkler for this?

Should they have water shields?

Should I have concerns for obstructions?

Any guidance would be greatly appreciated, thanks in advance.

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10 Comments

Pete

8/20/2021 06:34:40 am

I think it might be mentioned in NFPA 13 8.15.2 (2016 edition.)

schulman

8/20/2021 08:12:06 am

linen and trash chutes ? .... NFPA 13 Ch. 22 maybe ?

Matt

8/20/2021 08:15:24 am

I don't know if the guidance of NFPA 13 8.15.2 would apply here. This would be an application in excess of NFPA 13 minimums.

Can you tell us more about the shaft? Does it have landings at the floors? What is in it? are there access openings?

If it is wide open from top to bottom, I would definitely recommend water shields.

Could stuff be dropped down the shaft? Should the heads have impact protection?

Is the shaft conditioned? Open to atmosphere at the top and bottom where it might freeze?

Any additional details would be helpful

Glenn Berger

8/20/2021 08:19:20 am

Matt has it right! More information is required to provide good guidance.

Jesse

8/20/2021 08:19:33 am

Vertical shafts are covered in 2016 NFPA 13 Ch. 8.15.2

Trash and laundry chutes specifically are in NFPA 13 22.15.2.2.1

I sometimes forget Chapter 22 exists

Kenneth Casey Milhorn

8/20/2021 09:08:43 am

Besides the info in Chapter 22, just applying some common sense, I wouldn't think water shields wouldn't really do a whole lot to help heat collection, but could maybe help protect from mechanical damage if someone is doing maintenance on something in the shaft. Just like in trash and linen chutes, the alcove or shield provided is more to protect from mechanical damage or collection of trash/linen. Dangerous to assume, but I would think a pendent head, with guard and shield, stubbed 6 inches into the shaft on alternating floors would meet the intent, but that's just my opinion. It would be interesting to see if any fire testing has been done to prove the reduction in rating based on sprinklers in the shaft. I would feel very confident that that many heads in basically what is a chimney, will activate quickly and flood that shaft. The most difficult part of it might be trying to find a clean entry point into the shaft that is free of mechanical equipment.

Franck

8/20/2021 02:51:28 pm

Just one additional comment regarding the water shield: they won’t be beneficial at all to collect the heat (many studies have demonstrated that even larger plates above the sprinkler has limited added value), but would prevent water from above sprinklers to wet the thermal element and delay the sprinkler activation (just as for in-racks). In a vertical shaft, there are high chances that the top sprinkler will activate first. Sprinklers at lower levels would only be required in case of dramatic fire to avoid a possible lateral fire spread at lower levels. Thus the “umbrella” (water shield) to avoid a delayed activation.
But you’re right, just like guards, it would also protect the sprinkler from “falling items” like in a shaft collecting clothes… (hospital, hotel…)
A lesser problem in shaft only used for cable trays (but then, vertical fire separation is highly recommended as vertical fire spread on cables is more problematic as for horizontal cables).

Franck

8/20/2021 02:53:38 pm

As indicated above, more info is needed, in particular regarding what is expected in the shaft : cables, trash, linen, nothing…)

Alex

8/21/2021 09:56:13 am

HI Anonymous,

Similar to everyone else, I believe we need more information before we can truly guide you in the right direction. If the shaft is closed, continuous, and has no internal obstructions, alternating sprinklers would be more than enough coverage I believe.

Like Kenneth mentioned, shields are typically for mechanical damage not heat. Not stating that heat isn’t gathered as some plates are intended to collect gases to raise the temperature.

Looking forward to more information!
Thanks,
Alex

Shawn G

8/23/2021 08:49:08 am

The shafts vary in size and purpose, but in general they are mechanical shafts that will not be accessible. There are openings from floor to floor that vary in size, but many of them have openings roughly the same size as the interior of the shaft.

Even the shafts encasing the trash chutes have the reduced rating, so there will be a sprinkler in the shaft and a sprinkler in the intake of the chute.

In general the shafts are not open to atmosphere but they are not conditioned.

The shafts are filled with varying amounts of obstructions, such as ductwork, conduit, and mechanical piping. There are some where there is almost no room to wedge the sprinkler between the ventilation ducts and the wall.

I wouldn't anticipate falling debris.

TIA

How to Properly Sprinkler a Vertical Shaft?

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