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Confused by CMC - “combined” exhaust system?

Y

Yikes

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Southern California
Trying to understand the term “combined exhaust system” in light of this:

Single or combined mechanical exhaust systems shall be independent of other exhaust systems​

How can a system be both “combined” and independent?

Help is appreciated - I’m a multifamily architect who doesn’t normally deal with this part of the code.
 
Yikes said:
Trying to understand the term “combined exhaust system” in light of this:

Single or combined mechanical exhaust systems shall be independent of other exhaust systems​

How can a system be both “combined” and independent?

Help is appreciated - I’m a multifamily architect who doesn’t normally deal with this part of the code.
Click to expand...

Some furnaces and water heaters that draw combustion air from the outdoors use a concentric intake/exhaust so there's only a single penetration of the exterior wall. Could that be what this is trying to address?
 
You can't mix your furnace exhaust with your dust collection system....Is what I think it is saying.....Shirley you can mix sameilar appliances as long as the manufacturer allows it...
 
What type of exhaust systems does section 504 in the CMC cover? And is this the entire section or just a part of it?
IMC 501.2 has similar wording, but then expands into more detail than that. You can't combine different types of exhaust systems. you can combine multiple environmental air exhausts like bathrooms, but you can't combine bathroom and dryer exhaust. You can't combine type I hood exhaust with Type II hood exhaust. My guess is that's the intent, but without knowing the context of the CMC around that one section it's hard to tell.
 
Under the CMC, which is based on the UMC, I have apartments that are all-electric (no combustion gas venting.
I'm wondering if residential kitchen and residential bathroom exhaust can be combined into a single system.
 
Yikes said:
Trying to understand the term “combined exhaust system” in light of this:

Single or combined mechanical exhaust systems shall be independent of other exhaust systems​

How can a system be both “combined” and independent?

Help is appreciated - I’m a multifamily architect who doesn’t normally deal with this part of the code.
Click to expand...
I think it's referencing when a "whole house" ventilation system, or other single systems that cover multiple requirements. The Uniform version of what @klarenbeek said.
 
There are some HRV vents that have an intake one one side, and an exhaust on the other. It keeps penetrations down - one 5" hole does it all. I'm not even remotely fond of them, but the ones that I've encountered meet ASHRAE 62.2 - so they are legal. (At least on the buildings I play with in Canada.)
 
Klarenbeek is on the right track: a mechanical exhaust system that delivers different types of gases and air. etc need to be independent of each other.

Flue gas from a fossil fuel appliance can not be joined with exhaust from a dryer, bathroom, kitchen etc.
 
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