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Hood Support CMC 508.4

Hood Support CMC 508.4

Hood Support CMC 508.4

Does anyone have any commentary that explains why the California Mechanical Code (section 508.4) requires hood supports to be able to support an additional 800 lbs. beyond the hood weight? This is more than the hoods themselves in many cases.

Thanks in advance

RE: Hood Support CMC 508.4

When you say 'hood', in what context is this? I mean, what kind of a 'hood'?

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Hood Support CMC 508.4

In this particular case, it would be a type I restaurant kitchen exhaust hood

RE: Hood Support CMC 508.4

Apparently cooking area and grease collecting hoods.

See https://epubs.iapmo.org/2022/CMC/index.html page 143

It is so Bruce Willis and a team of commandos can enter the ductwork and find Hans Gruber.

RE: Hood Support CMC 508.4

"Welcome to the pantry, pal"


The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Hood Support CMC 508.4

Thanks- I did see that section of the CMC code. I was hoping for some background as to why this load is so high.
John McClane probably tops out at around 200 lbs, so it would take 4 of him to reach this load.

RE: Hood Support CMC 508.4

That's remarkably arbitrary.

If you have ever participated in the development of a code or standard then that wouldn't surprise you.

The California Mechanical Code is "based on the Uniform Mechanical Code".

The same 800 pound requirement appears in the UMC as far back as the 2012 version. I couldn't find any earlier versions in 2 minutes of Googling.

Good luck tracing things back farther.

RE: Hood Support CMC 508.4

To cover things that are hung off the hood?
To cover grease buildup?
To cover maintenance personnel weight times a safety factor?

RE: Hood Support CMC 508.4

Thanks. Good idea to look up commentary on older copies of the UMC, but I could not find anything more on this either.

RE: Hood Support CMC 508.4

The 800lbs. also likely includes an EQ (earthquake) component which should/might be applied in any direction. Other mech. equip., like water heaters and storage tanks must be tied back to the structure for lateral EQ loads too. You should always read the code commentary. That’s often more meaningful for a good understanding of the intent and original thinking than the code verbiage itself.

RE: Hood Support CMC 508.4

Thanks Dhengr,
Are you aware of any code commentary for this? I was not able to find any. Looking for that commentary was the purpose of this post.

The way I read this, Ev (from ASCE7) is separate (and additive) from this load.

RE: Hood Support CMC 508.4

I was just googling and ran across the online version of the 2021 International Mechanical Code. I don't see an 800-lb requirement, but do see "And the possible weight of personnel working in or on the hood" in 507.2.4 and a similar statement in 507.3.2.

RE: Hood Support CMC 508.4

Thanks Everyone

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