Sprinkler or Nozzle in Grease Exhaust Duct?

4/10/2019

We have an AHJ that is requiring a sprinkler be located in a grease exhaust duct - but I'm finding it difficult to see where this would be required (reviewed NFPA 96 and 13).

The duct serves a Type I kitchen hood, has an Ansul suppression system, and then has a roughly 45 foot run to exhaust to the outside. We haven't come across a requirement for a duct run like this before, is it required?

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9 Comments

Dave L..

4/10/2019 10:24:17 am

At least pre-2019 edition, start at paragraph 7.10 in NFPA #13.

Franck

4/10/2019 10:35:28 am

On NFPA 13, 2016 Edition, this is § 7.9 Commercial Type cooking equipment and ventilation. Became 8.9 in the 2019 Edition of NFPA 13.

Fire often occurs in grease exhaust ducts, mostly after fires on deep far fryers, extending quickly to the grease deposits inside the ducts. Fire could then spread to adjacent area/floors/levels as ducts are running through walls / ceilings.

Note that sprinkler protection is not required where all cooking equipment is served by listed grease extractors.
Sprinkler might also be omitted in the ducts, depending on their configuration.

An alternative solution could be the provision of a saponification system (wet chemical system - Class K in the US - designed for cooking oil).

PETE

4/10/2019 11:57:06 am

The Ansul R-102 system is a UL300 listed K-class wet extinguishing system. The duct protection stops with a single nozzle pointing up toward the exhaust. The exhaust is not interlocked because it aids in cooling. The hood return air and cooking power or gas are shut down. For long runs of type 1 hood exhaust, the preferred installation may be Ansul Pihrana which follows with water from above. But, note that IMC dictates duct clean-outs in the design. This is to facilitate periodicly cleaning the grease out of the duct all the way to the roof or exit point. With a Type 1 hood, Ansul R-102 should be able to protect. Check with the authorized Ansul distributor.

Mike

4/10/2019 11:57:37 am

Good responses above and AHJ has the authority to require anything they want. It's their jurisdiction.

PEte

4/10/2019 12:04:11 pm

I agree, but horizontal duct for type 1 slopes back to the hood. Flowing water over an existing Ansul installation may result in the Ansul not performing as designed and listed and Ansul not paying a claim if their system fails to extinguish.

Sue

4/11/2019 01:12:56 pm

I do not agree with the statement that the AHJ can as for anything. I am an AHJ and I must follow the codes. AHJs are not all knowing. I firmly believe that I don't know everything. If a customer has a way that is not typical, why not look at it.

We require a UL 300 listed fixed fire protection system or a fire sprinkler system designed for the type 1 hood. Having said that we also do alternate means and materials evaluations for special applications, which is allowed by code. If we do this we would take proposals from the customer and verify that the solution they are proposing meets or exceeds the intent of the code.

Nhat Nguyen

4/10/2019 08:23:58 pm

Both nozzle and sprinkler are allowed in NFPA 13 (you should see A8.9.2 NFPA13 2019, and that figure existed in previous version). The purpose of sprinkler or nozzle inside duct is for fire cause by grease attached on that, not for fire in equipment. Sorry for my bad English

Dat Huynh

4/11/2019 08:21:44 am

.... are allowed or are required?

Nhat Nguyen

4/11/2019 08:17:40 pm

It shall be provided. I mean you can use either sprinkler or nozzle for kitchen. NFPA 13 clearly stated that in 8.9 Commercial-Type Cooking Equipment and Ventilation.

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