Cold Air Returns

What is allowed to be run inside cold air returns i.e. wiring, plumbing, central vac, gas piping, etc? I’m guessing “none of the above” but I’m having a “discussion” with a builder so I need a code reference (Canadian).

Call your code department.

HI’s are not code enforcers.

Should that crap be in there, No.

But who’s to say.

Nothing should be allowed. I would refer it to the local fire inspector. or building code official

I’ve seen just about everything running through COLD air returns and joist runs…I don’t think there is any restrictions on this. The onlything I would watch for is electrical (110 volt) as it passes through a metal duct, this should have some type of bushing to protect it from sharp tin edges.

Return air and return air only. I can’t count the times I found other items running through these ducts.

How about this return air duct, stuffed with insulation. I knew something was wrong when the return plenum door slammed shut when I was attempting to pull it off…

there are some circumstances where the AHJ and the municipal codes allow the placement of electrical and plumbing to cross cold air returns (NOT RUN WITH THEM) COLD AIR ONLY. The penetrations should be sealed

I am very sorry for my post I saw after I posted you were in the North Country I have no experience that far north sorry again

I am not going to quote the IRC paragraph but from experience I can quote that nothing flammable as in vapor or toxic is allowed within a return or supply and I have found them all. Waste drains, Flue vents, gas lines

Alarm installers love to run their lines in returns! Even seen their loudspeakers in them. :roll:

If you want true surround sound, it is the only way

Rule 2-126 of the C.E.C., Part 1 permit type NMD90 cable to be installed in joist and stud spaces (i.e., cold air returns) in dwellings. It is recommended that type NMD90 pass through such spaces only if they run perpendicular to the long dimensions of such spaces.

I am not aware of any restrictions with regards to waste/vent and water supply piping inside returns.

Hi John,
In my opinion, it is bad practice to run anything through the returns.
The builder may be doing it because it was accepted practice from days gone by.
Having said that, it is still being accepted by building inspectors that if there are no other means to route wiring.
If you have one, check the building code book for it. I have an OBC and will check for you if you like. Any plumbing will promote moisture from condensation and as Darrell stated, if wiring, the penetration needs to be protected with a plastic bushing or grommet.

Thanks Darren and others. It looks like, at least in Canada, you can run pretty much anything you like through the cold air returns and not be violating any codes.

Heck, I think I have a mouse that keeps running through mine!
Out come the traps:roll:


I thought it was a weather report ! It is going to be -25*C here tomorrow night and lower later in the week!:shock: I guess that is why I assumed the weather report thing!