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Portable Air Purifying Respirator (papr) Materials And Build

Discussion in 'The Tool Shed' started by teletech, May 30, 2020.

  1. May 30, 2020

    teletech Member

    Santa Cruz, CA
    Aug 20, 2016
    Executive summary: you can build a PAPR setup for not much over $100 with careful scrounging and it's totally worth doing.

    I was already on the road to a PAPR setup for my painting, but was reluctant to spend the $500+ to get going so I was paining with a regular half-mask and not enjoying it or it's potential health effects. I have a yearly fit-check through work so at least that means I have more of an idea about how well my gear works and training than most folks but still not great.
    Fast forward the pandemic. What PAPR sets are out there are $1200 and up and I can see utility for not just painting but a trip to the local market (I'm in/near an early hot spot). I know it seems silly to many of you to consider a full PAPR for protection against non-solvent airborne pathogens and pollutants, but I don't always want to shave before fitting a mask and having been through the training and testing know just how bad a seal you get if things aren't just so. I also have a face-shape that makes for an uncomfortable N-95 fit anyway. I had already been thinking about building my own setup with commercial filters, a 12V fan, cordless tool battery, and I'd bought a hood. Then it dawns on me, ?bay, of course. I had a hood and a box full of filters that spin-on to a 3/4 pipe thread, so I just went out and bought a blower and cobbled it all together. After I built it up I tried some new primer, I couldn't tell you in the slightest what that stuff smelled like until I took out the trash the next day, it was that good. I iterated a few times, I'll give details below but I'll summarize with the facts that I could have managed to make it work for $100 and things I found around the shop, it was a huge improvement in my safety gear, and I've iterated several times so I am actually over $400 in at this point but have three hoods, two blowers, lots of hoses, filters, etc. and a better understanding of what it's all good for.

    Hood: I bought something random and sort of cheap from McMaster or MSC before I really got started. I thing it was for supplied-air rather than PAPR. Tyvek and a clear window. It had a tyvek connecting hose with a foam noodle in it and what appeared to be a standard (garden) hose end. The foam was lousy for airflow when I was low on filter surface area and also tended to get kinked or crushed so I removed it and shoved a hose up the sleeve. Much better airflow but things got a lot louder in the hood.
    These looks pretty similar and I'm sure would work fine:
    Allegro 9910-10 Replacement Hood with Suspension (w/o downtube)
    Since you cant turn your hood, I thought a little better peripheral vision would be nice so I bought a clear plastic hood. Problem is with the increased plastic thickness and the fact it's all around you, it's much harder to hear outside sounds and also reflects you own voice. The Tyvek also tucks in under your shirt or whatever really well and the all-plastic item from nuclear-power-outfitters is just big and bulky. On the plus side, peripheral vision and by routing the hose up over the top you get more laminar flow over your face.
    Nuclear Power Outfitters SAR101 Supplied-Air Respirator Bubble Hood Protection | eBay

    I have dozens of activated-charcoal typical organic-vapor cartridges that will screw on a regular 3/4" pipe thread, so started there. At first it was one filter screwed to a pipe nipple tapped into a flat plate I cut to fit the opening in the Bullard blower I bought. This worked well enough but was clearly not enough surface area.
    Next I bought Some old Scott P100 filters (604100-50) Scott NIOSH Approved P100 Filters - PN 604100-50 - Box of 10 | eBay
    they arrived and had some weird thread on them I still can't identify. Being P-100 they were perfect for virus but not paint. I carefully cut the back off the filter and mounted the body in my adapter plate. Plenty of flow but LOUD.
    Back to the drawing-board (milling machine). Another plate with three holes for pipe nipples out at the periphery and I have three spin-on filters. Plenty of flow and somewhat reduced noise but still on the loud side of things. Since Bullard touted the blower as quieter than previous models I wondered if the filter was somehow magic. Later a correct Bullard filter came up for particles and OC,HC,... everything but the kitchen sink, so I ditched my custom adapter plate and shelled out $70 for a filter. Not much noise reduction to be had there and it's bigger than my adapter rig with three filters so not really any gain there.

    The first hood I bought had a hose with a garden-hose thread. I wasn't excited about it's flow so cut off the end and pulled out the foam noodle, then shoved a standard 40mm military gas mask (under $10) hose up the sleeve. Better flow and crush-proof but much louder inside the hood. I've ordered some Bullard hoses (also under $10 off ebay in q=3) and will see if that's a better solution.

    You could just use a fan out of an air-conditioned seat. That's what Ford did on the prototype for their Coronavirus-designed emergency PAPR. I bought a Bullard EVA blower for $45, just for the fan really since it had such an odd intake setup.
    When it arrived I was impressed by the build quality and such but was intimidated by the odd 6-pin battery connector. A little detective work determined the battery cable only really needed hot and ground of someplace between about sixteen and twenty-ish volts, so popped out the special connector and spliced the internal cable to bring out two wires. These I hooked to a 6S LiPO drone/RC battery, job done. On a 4A pack I get about 4-hours of run-time. I did disconnect the speaker since it's throwing some alarm. My guess is it's a low-battery alarm and a 20V cordless tool battery would be a better choice.

    In search of a better fan for shopping trips. I scored a Bullard PA-20 blower with a 5x5 HEPA filter and built-in battery.
    The batteries were shot but I just set a 2s LiPO pack in there, changed the charge connector and called it a working unit.
    Just HEPA, no not for solvent use, but fine for dusts and pathogens. I really like this unit even though it's really primitive compared to the later EVA blower, I mean like hot-glue-assembled for a certified medical device level of primitive, but it works and seems a lot quieter and lighter than the later unit, so if you can find one on the cheap and don't need the chemical protection, these are a great score.

    I'll see about some pictures when I get a minute.

    Note: I have lots of extra parts that didn't work as well as what I'm using now, but did work. If you need gear, feel free to PM me.
    Last edited: May 30, 2020
    timgr and Fireball like this.
  2. Jun 2, 2020

    durangotang Member

    Western CO
    Mar 17, 2010
    Cool build, I'm curious to see pictures. I have seen people retrofit firefighting masks for this use and even some of the new full-face snorkel setups... those have both peaked my interest because of the good vision.
  3. Jun 3, 2020

    teletech Member

    Santa Cruz, CA
    Aug 20, 2016
    Back of modified Bullard EVA, I plan to use a wider belt for increased comfort. Also front view of the 3-filter adapter and back of factory Bullard filter.
    Front of EVA, filter, and side view of 3-filter adapter.
    Bullard PA20, not for paint but nice otherwise. The unit came with a shorting plug which I yanked the cap off of and soldered a pigtail for charging.
    Also note the two air hoses, the white Bullard hose and you can sort-of see the US-military hose. The Bullard hose is more rigid, the US hose has a really tight and somewhat restrictive 90 bend on each side. Good for wearing under you MOPP gear and perhaps other things.
    White hood, this one is more comfortable the more it gets broken in.
    Hood from Nuclear Power Outfitters. The cylindrical nature of it makes it too big for me to tuck under my outer garments since I'm not that large a person.

    I have pics of the blowers internals I'll try to locate, but they are pretty self-explanatory.

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