Black mold on air vents

2,231 Views | 17 Replies | Last: 4 mo ago by eye-gor
gigemJTH12
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9:50a, 8/19/25
AG
we noticed a ton of black building up on our air vents.

the HVAC company is currently at my house removing them and cleaning them and installing an air scrubber. He said it should fix the issue moving forward

my wife is freaking out because it looked really bad on the inside of the vents.

who would I call out to test my house for harmful mold spores present in the house even after they clean the vents?
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RoyVal
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9:52a, 8/19/25
AG
you live in Texas...pretty common. I fight this as well. You need to open up the air vents, and put silicon sealer around gap between the metal edge of the air register box and the drywall. The cold air mixes with the hot air coming through the gap and causes condensation.
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gigemJTH12
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9:54a, 8/19/25
AG
good analysis because thats exactly what they are doing now as well as installing the scrubber.


my allergies have gotten so bad only when I am at home so I am hoping this helps.
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Ryan the Temp
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12:31p, 8/19/25
AG
Spray it with Concrobium.
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drummer0415
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2:18p, 8/19/25
AG
Mold only grows on organic surfaces. I.e wood, drywall, etc. Mildew grows on inorganic surfaces like plastic, metal, tile, etc.

Assuming your AC vents are plastic or metal, the black stuff you're seeing is mildew, not mold. Similar to black mildew you may see in a shower that hasn't been cleaned in a while. Although it's unsightly, unless you're licking it off the vents it's not nearly as much of a health concern as people mistake it to be. Certainly not as much of a concern as actual mold growth.

Just wanted to let you know that so you and your wife aren't freaking out about "mold" in your air.

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gigemJTH12
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In reply to drummer0415 • 2:46p, 8/19/25
AG
I very much appreciate this post! and yes that is the case.
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BlueHeeler
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7:03a, 8/20/25
AG
What is an air scrubber? Is this a device that is installed in the plenum? Or, do you mean a stand alone unit that they will be removing after running a certain amount of time?
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gigemJTH12
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In reply to BlueHeeler • 7:13a, 8/20/25
AG
this is the one they installed

https://jacksonsystems.com/product/aerus-air-scrubber-9960051-a1013p-whole-home-air-purifier-w-activepure-technology-for-surface-air-contaminant-reduction/?srsltid=AfmBOoqV8POdfe1ucPf2Wzsx51kfY8_EJTN6UDdaGwbrG0qLNZpb_le0
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BlueHeeler
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In reply to gigemJTH12 • 7:43a, 8/20/25
AG
Thanks. I am going to look into this. Also, just FYI, don't tell anyone about anything related to mold. Especially neighbors. This could come back to bite you if you try to sell the place.
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gigemJTH12
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In reply to BlueHeeler • 7:45a, 8/20/25
AG
good point!

yeah look into the scrubber. Apparently works well for removing allergens and other unwanted particles. And relatively cheap.
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shalackin
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8:04a, 8/20/25
AG
This summer has exposed a lot of this in Oklahoma due to humidity levels and rain. We have been working with engineers and clients this summer on this type issue. It is amazing how many HVAC companies don't have a good understanding of true climate control. They run their calc for tonnage and that is all they know. They don't get deep enough. Positive/Negative pressure, water vapor, proper air turnover, exhaust, fresh air, dew points, etc..... it is more than just a Manual J calc.
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KingofHazor
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In reply to shalackin • 12:05p, 8/20/25
shalackin said:
This summer has exposed a lot of this in Oklahoma due to humidity levels and rain. We have been working with engineers and clients this summer on this type issue. It is amazing how many HVAC companies don't have a good understanding of true climate control. They run their calc for tonnage and that is all they know. They don't get deep enough. Positive/Negative pressure, water vapor, proper air turnover, exhaust, fresh air, dew points, etc..... it is more than just a Manual J calc.

Good point. But how is a consumer able to determine which HVAC companies are good and which ones aren't? I've found that the big companies are just as bad or worse than the little ones.
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shalackin
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1:27p, 8/20/25
AG
That is extremely difficult. I would suggest talking to a mechanical engineer and asking for a referral. The bigger companies are typically worse in my experience. they have a lot of turnover and make their mint on marketing for service contracts, not knowledge.
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Milwaukees Best Light
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In reply to gigemJTH12 • 2:08p, 8/20/25
AG
gigemJTH12 said:
this is the one they installed

https://jacksonsystems.com/product/aerus-air-scrubber-9960051-a1013p-whole-home-air-purifier-w-activepure-technology-for-surface-air-contaminant-reduction/?srsltid=AfmBOoqV8POdfe1ucPf2Wzsx51kfY8_EJTN6UDdaGwbrG0qLNZpb_le0

How does this work? It is not clear in the link. I didn't see any kind of filter. I am guessing it is electromagnetic. How often do you have to clean it?
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BlueHeeler
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In reply to Milwaukees Best Light • 5:10p, 8/20/25
AG
I had the same question. ChatGPT says a UV light and "Catalytic Reaction: This interaction creates powerful oxidizing molecules, including hydroperoxides, superoxide ions, and ozone (in this model)." I think I would have to do some more research on the 2nd part. I am not even sure what all that is, besides the ozone.
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Milwaukees Best Light
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8:15p, 8/20/25
AG
The uv is the part that bothers me. If I recall properly, those bulbs only work for a couple months. They will still turn on, but don't hit the frequency necessary to do the job. All the oxides and peroxides are just using catalyst mesh and probably electricity. That should last a long time.
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Thisguy1
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8:02a, 8/21/25
That looks like something the EcoZapp yahoo used to post on here all the time.
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eye-gor
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8:19p, 8/26/25
AG
Mold can very well grow ON inorganic matter, (i.e. metal) with the presence of "food" such as dust.

Mold needs moisture and food at the right temp to grow. While it is true that it will not feed on the metal itself, it can very well grow on it.

Shoot me a note separately, I deal with this daily as a TDLR certified MAT. I'll provide some further guidance.

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