FM Requirement for Height of Skylight Sprinkler?

3/4/2026

How should the new provisions in FMDS 2-0 (2025 Edition) regarding skylights in storage areas (sections 2.5.4.1.7 and 2.5.4.1.8) be correctly interpreted?

I have two cases based on the flowchart from the snippet below. In both scenarios, sprinklers will be required (even in the case highlighted in the green rectangle, which is optional).

My question is: Should they be installed at the base of the skylights, at the same level as the surrounding ceiling-level sprinklers (similar to Option 2 for skylight protection in the 2023 edition of FMDS 2-0)?

Or should they be installed inside the skylight, close to the highest point of the skylight (similar to Option 1 for skylight protection in the 2023 edition of FMDS 2-0)?

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4 Comments

Pete H

3/4/2026 06:30:09 am

One of your pockets is less than 18" deep, so between the top and the bottom of the pocket, it really doesn't matter. It will cover heat collection in that 18" ceiling pocket. The advantage of option 1 is less worry about cold soldering adjacent sprinklers.

Your other pocket that is greater than 400 cubic feet.... that one I'd do closer to option 1. That's a good amount of heat collection where you want to address the specific pocket protection.

I'm basing this on nothing beyond personal estimation of spray patterns. I can be entirely wrong.

Anthony

3/4/2026 07:43:40 am

Put the sprinkler ~ 1 ft down from the top of glass. Use a 212°F sprinkler.

Are the sky lights also a smoke exhaust vent that pops open during a fire? I'd be interested in the knock on effects there if anyone has insight.

Ewelina

3/5/2026 03:17:12 am

In Poland, this is the most common configuration due to local regulations. I am referring to continuous skylights equipped with smoke vents, which is the case for the scenario mentioned above. These vents are also used for comfort ventilation (opening during non-fire events).

FM DS 2-0 (2025) stipulates that smoke vents must be protected by sprinklers installed at the ceiling level (the base of the vent). This creates a bit of a dilemma: it seems counterintuitive to protect the main run of the skylight with sprinklers at the highest point ( Option 1 in FM DS 2-0 2023), while dropping the sprinklers to ceiling level only where the smoke vents are located within that same run.

Anthony

3/5/2026 09:39:42 am

Very interesting, thank you for your insight.

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FM Requirement for Height of Skylight Sprinkler?

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