Sound Attenuators on Ecology Units Exhaust Dcutwork

[Buildtech2]

In my current kitchen ventilation design, I did not propose any sound attenuators on the ecology units' exhaust ductwork because grease is present in the exhaust air, this grease can build up in the sound attenuators and cause a fire hazard. In this situation, a different noise mitigation solution is needed but our acoustic consultant is saying that there are no written standards for not considering the sound attenuators in the kitchen exhaust ductwork and he has done several acoustic analyses of the kitchen ventilation system where he already proposed sound attenuators in the ductwork of kitchen exhaust. If anybody knows a code reference that restricts the sound attenuators on the kitchen exhaust ductwork, please share it with me.

 

[EnergyProfessional]

I think the burden of proof is on the acoustic person....

Did they propose a product with the appropriate certification? There is a whole slew of JHA and code requirement for kitchen grease and among other things it needs to be cleaned (and be cleanable!). So if the acoustician wants a device, he should point to one that will be legal. I'm not aware of one, and find it hard to imagine how it can be cleaned. Maybe there is a solution, but you also should ensure a local grease duct cleaning actually is able and willing to clean it.

Code probably doesn't exclude a specific item, but it requires all items in the exhaust path to meet certain requirements.

You also should ask YOUR JHA. it may be the local Fire Department, or someone else.

 

[LittleInch]

Then you need to filter out the grease before it gets there??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EnergyProfessional]

Are you actually aware of an approved solution employing filters? You would have to constantly replace filters and ensure there is zero bypass or other way for grease to go to the sound attenuators. And it has to be approved by JHA.

I'm not saying your idea doesn't work, I don't know. But if you propose a solution, I wonder if you actually know this is feasible (legally)?

 

[nuuvox000]

Here's something interesting I found with a quick search; maybe you want to contact them: Vibro-Acoustics’ No-Media silencers do not contain any media. Rather, they rely on tuned chambers that operate on Helmholtz resonance principle.

https://noisecontrol.vibro-acoustics.com/applications/exhaust-systems/

 

[EnergyProfessional]

You can build silencers without any media... car mufflers are all metal. But you still need to clean them and any muffler will have some sort of baffles, perforations etc. That will be hard/impossible to clean.

Ultimately the product used must meet the code requirements, which may include UL certification and others. if it isn't listed for the application, or JHA gives approval, no one on this forum can "allow" the product. No matter how good it looks.

Reason they need to be cleaned is that accumulated grease is a fuel for fire. In case of a fire (or just heated air) goes up, you will have a burning stack. and guess what, there typically is a fire just below called the stove. So this isn't a requirement some bureaucrat invented out of boredom.

 

[Buildtech2]

Thanks, everybody for your valuable comments. I do agree with energy professional to use silencers without any media. Therefore, I would also prefer selecting the attenuators that do not contain any media to avoid grease-related accumulations. Rather, such silencers rely on tuned chambers that operate on the resonance principle. I will try to collect more information from local vendors about such special types of silencers that can be installed on the kitchen exhaust systems without any cleaning requirement