The truth is, I dont know what the airflow rate of an Okaysou AirSlim6C air purifier actually is.  Thus, your concern is legitimate, even though the airflow rates of these pumps doesnt "seem to be" excessive (i.e. not anything like the inflation pump when run at 12V), particularly with the hood-load in place, exhausting under a jacket with some pressure partially inflating the hood part.  It's a good concern and thanks for raising it.  I've attempted to build a flow measurement device, using a laminar flow element built from a multitude of plastic straws crammed into an 8" tube, but I have no means to calibrate it besides a single point pressure measure of the Delta BFB1012M and one other much stronger Delta fan I have on hand. - against the manufacturers spec curve.  When I was employed at Intel, I had access to calibrated airflow measurement systems that could easily determine the flow, but that would be at a guess backpressure based on what the hood inflation feels like when wearing it, exhausting under a jacket.  I've taken delivery on a 4th $10 Okaysou filter for assembly into a 2nd BFB1012M based hood pump for a spare.  The other filter option I have on hand are HEPA vacuum cleaner bags - which work, but I suspect the Okaysou filter has much more filter surface area by design.  If you were to ask "how much", well, I wouldnt have that answer in sq in either.
  Thanks for your interest and compliment!

Nice project and write-up. How much air does the Okaysou AirSlim6C air purifier move per minute? Is it less than your pump moves? I tested some filters with airborne cornstarch dust (using iodine and water to detect what got through) and noted decreased filtration when I pushed airflow beyond what the filters were made for.

A couple more grocery trips under my belt.  These days, no one bats an eyelash seeing me wear this.  Working on the Delta BFB1012M fan based filter, for the luxury of quieter operation.  Turns out the 70C sanitizer melted the hood window (so now it's all warped) and headstraps of other respirators I put in there.  Probably needs a small fan to circulate the air within, as clearly there are hot spots within the box, using the hysteretic (on-off) controller.  A mistake to expect it to "just work" without consequences - I should have realized something could melt under the lamp, while on the way to 70C at the temperature sensor location.

Tried to do 3 stores grocery shopping on one battery and - didnt work out.  Ended up running back out to the car for the 2nd to refresh things,  Learned best to keep a spare in the pocket!  A couple of folks actually seemed interested, one asking where I got the hood.  This week I built the 70 deg C sterilizer, using a discarded styrofoam chest for shipping dry ice, a 500W floodlight bulb along with a $20 temperature controller I got off ebay.  Works excellent, just put the hood and filter pump in there, let it reach 70 and hold for a few hours - same for the respirator masks, hats and gloves we wear when going out.       

Another shopping trip for the week; two stores done, one battery. Staring to sound like a broken record, but I'm gaining confidence in the design; enough that I dont even need to bother with the extra backup battery.  I picked up a Eastman 8ft washing machine discharge hose from Lowes that has a larger diameter and far less restriction; I had to glue on a 1" piece of PVC tube to be able to clamp it to the hood intake port - the other end cut to fit the pump output snugly using the rubber grip that came on it.  The diving mask  / Delta server fan filter combo is coming along and it's going to work out nicely too.  My GOOP is starting to run out! - it solves so many fit / seal / mechanical strength attachment problems!

Another shopping trip for the week; two stores done, one battery.  I'm getting used to being in this thing, even powering down for a few moments to have a brief conversation, as it is a little noisy in there.  A thin skull cap style knit hat takes care of any head chill from the moving air.  It looks like people have seen it all, only received perhaps a few curious glares, otherwise like being in a Halloween costume as "Corona Virus" guy.  Whatever, I'm taking no chances after reading what I've read about this pandemic.  Many others had cloth masks on this trip, but still many with nothing at all.  I'm experimenting with a centrifugal computer fan and a full face diving mask I have on order and am considering a DIY airflow measurement system, to see if I can quantify the flow this setup provides - want 4 - 6 cu ft / min as a target.

A grocery shopping trip today went quite well; a single cell was all that was needed to traverse two stores.  I left the hood in place and the pump running while commuting between stores - simply unclipping the waist belt and setting the machine on the seat next to me.  Airflow was entirely adequate as far as I could tell - zero distress from heart / lungs / head as I went about in the stores.  I'm quite happy with how this has worked out and it was good to see more people than on the last trip wearing their DIY face masks!

Yes, my wife wont wear it for such reasons; the air is cold on the back of your neck and it's noisy (spent some time this morning pondering an unrestrictive airflow silencer design) and it does have some danger in rebreathing spent air to some degree - all of which gives her a stress headache.

Personally, I'm willing to put up with the consequential inconveniences for the touch conveyed and aerosol conveyed protection this particular device offers.  100% on touch, who knows what the filter actually does performance wise; pretty much all you can say is "better than" a leaky mask - or using no protection.   I'll take it!

One thing I never considered about PPE is claustrophobia - some people just can't take having something over their mouths. Didn't think about that until a friend told me his wife freaked out when she tried to mask up for a shopping trip yesterday. Not that this is pertinent to your build, just thought I'd mention it as an "unintended consequence" of all this.