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What is causing high PM2.5 in my new house?

Trevor_Lambert | Posted in General Questions on

We’ve been living in our almost-completed house for a few months now. Passive style house, 0.22ACH50 with a fully ducted HRV. We moved in right after drywall was (mostly, I had to finish some and fix a ton of mistakes) complete, and started doing the painting ourselves. The drywaller left a mess all over the concrete floor, which I have been gradually cleaning up. After a while, I decided to set up my Dylos particle counter to see how we were doing with the air quality. Not too good. It’s hard to say what the average was, but depending on how much we moved around in the house, anywhere from 10-100 PM2.5 (estimated, the Dylos actually reads in particles per cubic foot).

Over the last several weeks, I’ve been running a couple of air cleaners when we’re not home (these are super loud), and gradually getting the house cleaner. I haven’t seen an overall reduction of the particulate matter. When I come home and the air cleaners are running, the reading on the meter is near zero (<0.5). However, all it takes is to walk around the house for a little while before the numbers are up over 10 again. Similarly, at night when no one is moving about, we see readings of <3. So this tells me that whatever it is, it’s stuff that is heavy enough to be settling out on the surfaces, and stirred into the air with movement (but not significantly stirred by the flow of ventilation air from the HRV).

What I find most puzzling is the readings after turning off the air cleaners. They were running for hours with readings near zero, and these things push about 800CFM, so I would have thought they would stir up at least as much particulate matter as us walking around the house.  And yet, we start walking around the house and the numbers go through the roof.

So my questions:
where is this PM likely coming from? The unfinished edges of drywall (we haven’t trimmed doors and windows yet)?
what else can I do to lower the numbers?

We do have a recirculating range hood, but the pattern of high PM happens even if we haven’t cooked for days. I see a separate rise and fall of PM when the cook top or oven is used. I really don’t think what I’m seeing can be explained as days old smoke getting stirred up, but maybe I don’t understand the nature of smoke as well as I think.

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  1. Jon_R | | #1

    CFM doesn't mean much, it's about velocity and direction. Maybe you should put on a respirator and walk around with an electric leaf blower :-).

    1. Trevor_Lambert | | #2

      If I did that while the air cleaners are running, do you think that would help to drive the stuff at rest up into the air to be cleaned? I don't actually have a leaf blower. I have a 10,000cfm fan that is high velocity, but like the air cleaners, the air turbulence will drop to next to nothing once you get far enough away from it. I could just run around the house waving my arms, but that would be tiring.

      1. Jon_R | | #4

        Getting the particles into the air will definitely help with removal by air cleaners (or outside air ventilation). +1 on a HEPA vacuum.

  2. JC72 | | #3

    I suspect most of it is dust from the drywall and construction in general. You need to clean/vacuum everything. Gradually cleaning up isn't going to cut it. Use a vacuum which has a HEPA filter.

    You should also find out what is considered "normal" and "high" from an IAQ standard in your local area. Don't forget occupants will bring particulate matter in with them when they enter the house.

  3. Expert Member
    BILL WICHERS | | #5

    You need an “air cleaner” like the asbestos abatement crews use — a beefy blower unit with a HEPA filter. Regular filters won’t get drywall dust. Drywall dust is notorious for going right through regular furnace and vacuum air filters and putting a fine dust coating on pretty much everything in a house. That’s why everyone loathes sanding drywall when remodeling occupied homes.

    Electrostatic air filters also help, but extract far lower total amounts of stuff from
    The air.


  4. STEPHEN SHEEHY | | #6

    Trevor: You might try wiping down the walls. It's tedious. When we moved into our house we were astounded at how much construction dust was coating the walls.

  5. Avasa | | #7

    is your floor still unsealed concrete? could walking on this be creating particulate?
    (as we overlap in another thread, i am curious about this house of yours!)

    1. Trevor_Lambert | | #8

      It was up until recently. But even then, it was very smoothly finished, and I can't imagine shoes soles or socks actually abrading the surface. I'll see if the readings start to come down now that the floor is much cleaner and I start to spend some more time vacuuming.

  6. CMObuilds | | #9

    Was your floor saw cut? If so have you vac'd the cuts while taking a blade to loosen up all the dust/dirt at the bottom with a hepa vac?

    I live in a very tight house and I have noticed a lot of lint particles from machine dried laundry. My theory is the dryer isnt getting enough makeup air so lint removal isnt as effective, something to check anyways.

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