Indoor Air Quality/Duct board and mastic


TJ, I thought our symptoms had improved but it just took a couple days for them to show up again after being away from house for 3 days. I had an industrial hygienist come over with a PDI monitor that shows any levels of VOCs in areas. Nothing showed up. Looking at the MSDS for the mastic and rolled duct adhesive used we only found methyl alcohol in the mastic as a possible issue. The rolled duct tape didn't have a MSDS just a letter from OSHA saying it didn't need one.  The mastic and tape were by Hardcastle, liquid sealant duct seal 321 and rolled sealant grip 1402.  Do you know anything about the duct tape?

Also, we had extreme formaldehyde exposure previously and I feel we are sensitive to it in addition to other chemicals. When we put the PDI monitor in the area at the bottom of the furnace where the air blows through I saw the duct board with unsealed edges....yellow fiberglass showing and everything. My other question is....can the duct board be removed from the unit and if so what do we do for insulation there? Is there more duct board in other parts of the unit that we can remove? It's a dual fuel two stage 95percent eff furnace and air conditioner by Amana.

Thank you.

Hi Stacey,

As far as the tape, beyond what you have already investigated no.

Now with the duct board being fiberglass, and fiberglass has formaldehyde in it, and your sensitivity to that, then definitely need to have all duct board sections changed to sheet metal. The duct board sections can just be the plenums only, but it very well may the majority of your duct system, minus any flex supply branches that may be installed as well.

Now the sheet metal has to the insulated, and traditionally that done with duct insulation which has fiberglass in it. Granted it's not in the air flow, but it may be best in your situation to have the sheet metal wrapped in foil bubble wrap. It's mainly used in radiant barrier applications, but it can be used as duct wrap insulation as well.

Something else to consider...I believe you had mentioned that you do not keep a car in the garage. But do you store anything else in the garage like gas, paints, cleaning products, etc?? If so, then it is possible that there's enough fumes from those products are getting pulled into your duct system to cause your symptoms. With a the section being unsealed, it pulls in whatever air nearby, and cycles it into your home. So make sure that the contractors properly secure the duct sections air tight to the furnace and elsewhere...especially the "hard to reach areas" on the backside & bottom.

Stacey, I hope this helps, and please let me know what you find out.

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TJ Nichols


Hello, I'd be glad to answer your questions on IAQ & other related issues!


My approach is to treat the home as one system with individual working parts. Think (TEAMWORK). When one or more areas (PLAYERS) are failing or bad, it affects the whole system (TEAM) to operate less efficiently. I aim to address the problem, not just the symptoms, to offer better solution options.

High School Grad (06/1991)(VA) EPA licensed & certified in Types I & II Refrigeration (04/1997)(MD)

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Have served tens of thousands of customers over the course of my career

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