A modification of the USCSW V2 design, to make sure the front part doesn't fall off; this is now a 2 part file and prints faster, and is safer. Air flow is exactly the same as the original (or a tad higher)

The front slit was molded into the mask and a hole for a pencil to push the grid piece out of the inside to change the filter.

At USC-Keck, they are snapping HEPA filter fabric between the grid and the inside of the mask, so I created a flatter version without the original chamber. This ensures no air gets past the filter pad.

 

For assembly instructions, see external derivitive sources.