Sprinklers Req'd for Large Ducts >31" Below ESFR?

I am working in a warehouse with an existing ESFR system at the ceiling level. The new tenant is going to have manufacturing occupancies below, with no high-piled storage. We are utilizing the 2025 edition of NFPA 13.

There is a lot of ductwork being added to the spaces, and a question has come up regarding round and square ducts between 24 and 48" wide/diameter, and if protection is required below.

For example, there is a series of (5) 42" Ø fabric ducts (Ductsox) running across a space. The top of the ductwork is approximately 6' below the deflectors of the 16.8K ESFR sprinklers overhead.

When looking at section 14.2.10.3.4, I am interpreting the rules as follows - If a fixed obstruction is larger than 24" wide, and it isn't placed in accordance with table 14.2.10.2.1(a), it will require supplemental sprinklers regardless of the distance below the ESFR sprinklers. Obstructions over 48" will still always require supplemental sprinklers, and obstructions less than 24" won't need supplemental sprinklers if they can comply with one of the options 2-6 in 14.2.10.3.4.

The confusion comes in with the reference to Table 14.2.10.2.1(a).

Others in my office are interpreting the rules to mean that since the obstruction is greater than 31" below the deflectors, it would be acceptable to omit supplemental sprinklers underneath.

I am of the belief that Table 14.2.10.2.1(a) doesn't apply at all since the obstruction is greater than 31" down from the deflectors - Since they don't comply with any of the other options in 14.2.10.3.4, supplemental sprinklers should be installed below obstructions between 24" and 48" wide when spaced more than 31" below the deflectors.

What is your take on this? Are sprinklers required for obstructions between 24-48" wide when more than 31" below the deflectors?

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