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
Construction & Materials
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. They are not recommended for use in a clinical setting but are fine for draft prints to test mask fit.
A 1/2" wide, 3/16" thick adhesive-backed sponge neoprene strip around the inside edge forms a tight seal. Thinner or thicker strips can be used to adjust fit.
Another strip of 1/8" wide 1/16" thick adhesive-backed sponge neoprene should be placed around the filter opening. The filter enclosure is designed so that when locking the cap, it compresses the neoprene to prevent leakage. The cap's locking mechanism is similar to a DSLR camera lens.
For clinical use, the straps can be made from self-adherent medical wrap. It's easily adjustable and its grippy texture prevents slippage. For general use, elastic straps work well.
Sizing & Fit
I designed this mask to fit NIOSH-developed headforms. I've posted the medium size and will add an additional 4 sizes (small, large, short-wide and long-narrow).
Further adjustment can be made to the mask by adding additional neoprene strips where there are gaps.
The process I've used for generating the 3D models is unique and fast because it is generated from a 2D flat pattern. The wall size is uniform.
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 during 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
If using surgical resin or MJF nylon, the 3D printed parts can either be steam sterilized or placed in an autoclave. For testing purposes, I provide PLA or PETG parts that have been soaked in 3% hydrogen peroxide for 30 minutes.
The filter, medical wrap and neoprene strips should be removed and disposed of after use.
