There are two newer versions of this design:

Cut & sew https://3dprint.nih.gov/discover/3DPX-014379

Entirely 3D printable: https://3dprint.nih.gov/discover/3dpx-015194

This project is still active as of December 2020. All files are available on a github repository http://github.com/basicrespirator/basic

Design Caveats

This device is intended to eventually meet criteria for a surgical N95 respirator, but it has not been fully tested. I have released the design as-is and will continue modifications. The mask fits well and forms a tight seal when properly fitted, but the design of the filter assembly may need to be modified to increase the surface area of the filter and slow air flow. If you have any questions about the design, please email me at basicrespirator@gmail.com

This is a partially disposable mask designed for emergency use. The mask is folded from a flat sheet of Tyvek™ or any other flat textile into a origami-like structure that's both rigid and flexes to conform to the curves of the face. A reusable 3D printed filter assembly inserts into an opening in the mask and accepts an N95 or similar filter. An aluminum nosepiece secures the top and a neoprene inner seal + gasket makes the mask airtight. The design is flexible and allows the wearer to talk and make facial expressions without breaking the seal.

Materials

For clinical settings, Tyvek® 1073B with 18B Xhale®Adhesive was chosen as a potential material because of its low cost, high BFE, breathability and ability to be sterilized. It is the same material as the packaging used to sterilize medical instruments. This material has not been tested for use as a face mask and DuPont has not approved its use in this type of application. 

Adhesive-backed neoprene is used for the inner seal and gasket for the filter assembly. 

Certain brands of neoprene and adhesives can survive sterilization in an autoclave.

Ideally, the 3D printed parts should be made from nylon using MJF or surgical resin using SLA.  FDM printing can create microscopic holes that allow small particles to penetrate and make the parts harder to clean. And they cannot survive the high temperatures needed for sterilization. FDM printed parts are not recommended for use in a clinical setting but are fine for draft prints to test mask fit.

Exhaust

There is no exhaust valve in the mask, the filter is large enough so that the wearer can breathe comfortably. I've worn it for up to 4 consecutive hours and performed strenuous activity without discomfort, but outgassing has not been lab-tested for professional use. 

Testing

This design has not been fully lab tested to ensure it meets requirements for a surgical N95 respirator. If you have any questions about the design, please email me at basicrespirator@gmail.com
 

Sanitization

Tyvek 1073B was designed as packaging for sterilizing instruments. If using autoclavable adhesive and neoprene, the entire mask can be sterilized using this method. 

If using surgical resin or MJF printed nylon, the 3D printed parts can either be steam sterilized or placed in an autoclave. FDM printed PLA or PETG parts are soaked in 3% hydrogen peroxide for 30 minutes. 

Production, Shipping & Assembly

The flat patterns can be created by hand or with a laser cutter to both cut the outside shapes and pre-crease the fold lines. Die-cutting is another option for mass manufacturing. The mask is designed for flat shipping. It can be assembled in minutes onsite with peel and stick double-sided adhesive and adjusted for a custom fit.