I’ve been asked to design a respirator cartridge that fits to anesthesia masks (possibly used and sterilized), and some CPAP masks (either sharing the same standard 22mm fitting or with adapters) as an emergency N95 alternative. I’m neutral on filter media, but researchers at UF identified using both layers of Halyard H600 surgical wrap as an effective medium when there’s enough surface area. However, their design doesn’t 3d print well, and is rather large and heavy.
I have a design that provides greater surface area of filter media for breathability, doesn’t depend on rubber bands, and is much lighter (47g printed in PETG, which is the heaviest of the common 3d printing thermoplastics). I’m doing some fine-tuning on that should go out for proper N95 testing in a few days once I’ve dialed in the parameters. I made an adapter that allows me to test with a CPAP mask I was given for the purpose (it has a standard 22mm fitting on one end, and the other end engages the CPAP mask taper) and it’s quite breathable.
@HalfNormal I know you’ve been concerned about amateur efforts here. Obviously this doesn’t replace the real thing. But it was driven by a physician in NJ asking for help because of physicians and residents intubating COVID-19-postiive patients without any shield or respirator at all, and my current plan is that assuming good results from an N95 test it goes next to NIH. Since this is your field, do you have thoughts in particular on availability of used, sterilized (or, if supply is not a problem, new) anesthesia masks? It’s the good face fit that I’m most concerned about; that’s the part I don’t really influence because it’s a cartridge not a mask that I’m designing.
Here’s the work in progress repository:
Here are pictures of it attached to a CPAP mask, with tape over the holes in the CPAP mask for a test seal.
The frames are meant to hold mechanically, but can and probably should also be taped together, front to back. Belt and suspenders.
Here’s a rendering of the design, showing the frames that hold the filter medium in place both as they are printed (next to the base unit) and also how they are installed on the base unit.