What are these things in/on HVAC duct? (furnace, AC, heat)

[Richard78]

We have a 1-year old ranch home in WI. The ductwork has these smaller and larger, what appear to be duct plugs of some sort everywhere on the ducts. What are these for? Why are there so many?

Our builder who doesn't do anything for free, weirdly had our ducts cleaned for free before we moved in. I've seen this on ducts online but they only seem to be in 1 location. We had our ducts cleaned previously in our 10 year old house and we never saw these plugs.

There are 11 small ones and 3 large ones total that I can see.

[Ghengis]

I'd get another hygienist out and have them look (camera) into that particular section of duct for any construction debris in there, perhaps they introduced a lot of drywall dust and used the penetrations to either attach vac equipment or to scope that particular section of ductwork

in industrial applications they use duct penetrations of that type to measure and balance air distribution, but why you have them in only one area is a bit odd

some of the penetrations could be used to measure any potential gas contaminates from your furnace entering the airstream but that I think is typically done within the furnace itself

I wonder why the two penetrations in the second pic are at what would appear to be a low point, do you have any signs of moisture (rust or white deposits) at any seems or joints in your ductwork?

[Hawekeye2011]

Very odd. Do you have any duct work that supplies the basement? Is the basement finished/heated?

If so it might have been a cheap way to get a little AC or heat down in the basement without adding duct work with registers in the basement.

[davebarnes]

My old house had many of these after Coit came and cleaned out our ducts.
They provide easy access for cleaning tools.

[K'ledgeBldr]

They are/were access points for duct cleaning.

To what extent or degree of satisfaction? Well,...

[Richard78]

Originally Posted by Ghengis

I'd get another hygienist out and have them look (camera) into that particular section of duct for any construction debris in there, perhaps they introduced a lot of drywall dust and used the penetrations to either attach vac equipment or to scope that particular section of ductwork

in industrial applications they use duct penetrations of that type to measure and balance air distribution, but why you have them in only one area is a bit odd

some of the penetrations could be used to measure any potential gas contaminates from your furnace entering the airstream but that I think is typically done within the furnace itself

I wonder why the two penetrations in the second pic are at what would appear to be a low point, do you have any signs of moisture (rust or white deposits) at any seems or joints in your ductwork?

We had our framing up when the plumber did something with the main water valve which caused water to flood the basement for a couple of days. After that a mold remediation company came in and sprayed something on our exposed framing. Exterior was up and framing but not insulation when flooding occurred. Not too long after did they do the insulation and then drywall.

Should we have someone look into the ducts and see if there is an issue? Any other thoughts on what this could be? The basement is finished except for in the furnace area.

[Richard78]

Originally Posted by Hawekeye2011

Very odd. Do you have any duct work that supplies the basement? Is the basement finished/heated?

If so it might have been a cheap way to get a little AC or heat down in the basement without adding duct work with registers in the basement.

The basement is finished and we have a zone control system - 1 zone for the main level and 1 for the lower.

[Ghengis]

Originally Posted by Richard78

We had our framing up when the plumber did something with the main water valve which caused water to flood the basement for a couple of days. After that a mold remediation company came in and sprayed something on our exposed framing. Exterior was up and framing but not insulation when flooding occurred. Not too long after did they do the insulation and then drywall.

Should we have someone look into the ducts and see if there is an issue? Any other thoughts on what this could be? The basement is finished except for in the furnace area.

you might ask your contractor why he felt compelled to make all those penetrations. I don't know why they would have to clean the duct work prior to any sanding. Even then really no reason to, especially since the air likely wasn't circulating. It wouldn't hurt to have someone come in and look at the inside of the duct. Probably nothing in there that would promote mold growth but it wouldn't cost much to take a peak. Was the leak in the basement and not upstairs? To be real safe I'd have an industrial hygienist come in and take a good look at the basement. Bet you could have a thorough inspection done for less than $150 and provide yourself some peace-of-mind if nothing else.

Ask the contractor what "something" they sprayed on the framing and ask him for the MSDS (Material Safety Data Sheet) of whatever it was. Bleach does not eliminate mold. My feeling is that it's probably nothing to be too concerned about.

[Nonesuch]

If you're more of a DIY person, you can buy an inexpensive semi-rigid digital USB borescope (endoscope) from Amazon or eBay for much less than what you would pay for an inspection. Also handy for looking in any other tight spaces -- walls, plumbing, etc.