This mask was developed with the intent to utilize, whenever possible, materials that could be sourced with workable lead times and with minimal impact to the medical supply chain. 3d printing was explored, but our team quickly realized that as a production process, 3d printing was too slow and expensive and we lacked the resources to scale it. These constraints led us to experiment with vacuum forming, for which we built our own vacuum former and used the resin 3d printers to produce the "bucks" or molds upon which we pressed the sheets of .060 PETG plastic. If adopting this design for vacuum forming, be sure to include enough shell layers and infill. 

With that said, these masks can be 3d printed! In fact, the design works well for that. We used Form Maker II Grey Pro engineering resin as well as grey and clear prototyping resins. 

We chose to use a .060 PETG plastic because those making face shields tended to use .030 thickness and we wanted to preserve those supplies. In addition, instead of using elastic for the straps, we elected to use 8" rubberbands which are inexpensive and easy to source. The filters were cut from Filtrete 1900 MPR Electrostatic Pleated Air Filters purchased at Lowes. It meets the .030 micron threshold. This material can also be purchased in bulk from various distributors and we are not endorsing any individual provider. If purchased as an assembled filter intended for home HVAC use, you will first have to remove the paper frame and metal wire layers on the outside of the filter before being able to size and cut for your masks. We found that by first cutting the frames , the metal wire easily peels off.

Regarding the foam utilized in the inside of the mask, we used 1/2" W x 3/16" black neoprene foam stripping from Grainger which we bought in 50 foot rolls. The item # was 420C27. Each mask used approximately 13". Initially, we were only installing the foam near the bridge of the nose, but later discovered it was more comfortable and created a tighter seal if the foam went completely around the inside of the mask. 

Based on my calculations, this mask cost $6.42 in materials to assemble a kit which includes the foam lined mask itself, 10 filters, 2 rubber bands (straps), 2 plastic sealable bags (1 for the filters and the other for the mask and all its accessories), and a set of instructions which we printed out in color.

I would like to extend a very special thanks to Matt Heck, who volunteered his genius and many hours, Leon Wylde and his crazy good CAD capabilities, and Stefanie Bryan for enabling us access and acting as a liaison to the firefighters who tested these masks.