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Thoughts on recommended Air Filter max MERV rating for MDF dust?

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  • Thoughts on recommended Air Filter max MERV rating for MDF dust?


    Setting up a large spray booth-like enclosure in the garage using mostly what's on hand.
    The size of the area is roughly 8'H x 10'D x 10'W and no top initially.

    If enough positive pressure exists it won't be needed, although I'm expecting not generating quite enough pressure with the filter in place so a top is planned if required. I'll find out later.

    Good roll of painters plastic (10'x100'x), few hooks, bungee, Velcro and most importantly a positive air flow condition.

    Forced air will act similar to a positive pressure Corsair 900D Monolith case I built years ago. Dust can't enter (within reasonable micron). It's simply rejected.

    The sole fan will be a Caterpillar variable speed shop fan capable of 4000 CFM wide open. It's a nice blast with a 17-1/2" rear flared opening.

    Experimenting today I picked up a washable MERV-8 filter, in process of adapting to fit the fan.

    I'm pre-cleaning and blasting so the amount of available dust at the outset is dramatically eliminated, plus no "new" MDF dust will be generated inside the garage during the finishing stages.

    So, that's the rough scenario.


    Who has messed with positive pressure inside decent size DIY booth-like constructs and what maximum MERV filters did you find worked well given your particular CFM to keep MDF and other dust out?

    I stopped short of entering MERV-9+ territory as I just don't want to choke the fan any more than necessary to keep reasonable pressure going.

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    Any on-hand experience specifically with MERV + CFM + MDF dust in positive pressure areas (not small boxes ) would be valuable.


  • #2
    This is a paint booth? For industrial paint booth we'll use merv-8 filters in a pull through arrangement. The incoming air is clean with few contaminates. The air is also moving in the booth so there is no overspray or particles to settle on the finish.

    At home most of the finishes I use (including the waterborne stuff) flash off pretty quick so there are not many particle issues. I do use a merv-14 filter in my dust collector to capture MDF dust.

    Note that positive pressure does nothing to control the particles in the booth or those created by overspray. It would also be dangerous if you plus sprayed solvent based finishes are in this booth
    John H

    Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower


    • #3

      Thanks for the info and stuff to consider. I've just finished the first experiment and the MERV-8 cuts the CFM of the fan too dramatically as configured for real positive pressure. Presently it's directly attached to the back of it.

      The positive pressure was simply to help keep out anything not already in it. Location and technique will account for overspray. I'll actually be using an extendable car mop and windex to clean the inside top to bottom before each session to further reduce any dust that may be inside.

      It'll all be enamel primer and base, though if you're talking about powder coating or anything involving electricity in your warning - no this is just a Q&D "booth like" construct for HVLP enamels thinned at, most likely, 12% so 8:1 paint / naphtha, for primer and base.

      Updated: Also in case you meant ESD, though I assume you didn't, I have a full strap kit but not aware of any (of my intentions within the enclosed areas) that would trigger the need to use it.

      I'm basically just trying to ensure the cleanest working area I can muster with on-hand material and ingenuity. As these are
      Alkyd enamels (according to PSD) cure times are a concern but the biggest is giving the surface enough time in a clean site to set before bits of crap can settle and ruin so much work.

      Plan B looks like a push pull is probably the only way I'll be able to achieve this goal so I'm headed toward that now.
      Last edited by Thump; 08-12-2018, 06:54 PM. Reason: Expanded


      • #4
        This sounds seriously dangerous, both from an inhalation and flammability standpoint. You should read a Safety Data Sheet (SDS) or Material Safety Data Sheet (MSDS) on your products.
        John H

        Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower


        • #5
          It's not seriously dangerous (in the way I'm planning on doing it), at all. You must be reading far more into it, but I seem to fail in describing things very well, often, so I'll assume it's just me.

          Ventilation is plentiful, as are my respiratory equipment, the limited equipment that'll be inside the "enclosure", the specific restricted use of the space and many other factors. Your concern is appreciated none the less and thanks for the input.

          Nothing will be exploding, burning, scalding, combusting or choking me to my demise.

          By the way, I've read every data sheet that came with the enamels I purchased when I bought them.

          Instead of thinking you're assuming I didn't, I'll instead "assume" you're just err on the side of caution and recommending I do so in case I haven't. Those materials are vital to understanding a hell of a lot more than danger. Flash and cure times at certain temps and humidity levels being the most relevant to me, but that's because I already take safety precautions out of habit since I enjoy being alive.
          Last edited by Thump; 08-12-2018, 08:31 PM. Reason: Enhanced


          • #6

            Added the MERV chart I used as reference when I was originally looking into this subject. There are many but I liked this one in particular due to format and details:

            MERV chat

            Original source from which I derived the image:

            Last edited by Thump; 08-13-2018, 09:33 AM. Reason: Clarified