The main advantage of this mask are the Cartridges.

Why Cartridges?

Replacement Filters
Easy to Vent
Easy to Build

The design is built off the MSA Half Mask. I've had this handy piece of equipment in the shop for years.

The version shown here is a working prototype. The current version is shown in the final step. If you make it that far and have experience with injection molding closed cell foam or silicone please DM.

Unfortunately in much of the world where masks are apart of the 'new normal' life where we extend social distancing by wearing masks. If you are lucky enough to have friends in Asia you can learn more about where things are likely to go for us in the West.

Disclaimer: This is a prototype. It's a way of designing a mask that could produce a better way to manage a reusable mask 'base' with replacement filters. Please consult the CDC and do not see this as direction for how to guarantee your personal safety.

Supplies

Model for Reference - MSA Masks - sadly as of 3/31 all are unavailable on amazon... link

Milk Jug - this is the standard 1gal in the US. Look for something similar in other parts.
Window Insulating Foam- mine is 1/2"x3/4" but it doesn't need to be so thick. here's 1/2"x1/2"
Pill Bottles - best are these new ergo type with a double screw ends. ---mine are from walgreens but I found the same type on amazon... link
Disposable Glove- rubber gloves
Silicone
Sand Paper
Drill + Bits
Rubber Bands
Tape - Electrical and Ducts
Stapler + Scissors
Filter Fabric - ideal is to have rated materials at n95 or greater... in a pinch a high quality air conditioner filter that filters to 5 Microns --available on amazon and can be re-purposed. Confirm with a site like iallergy.com that compares level of filtration. The virus itself is far smaller than 5 microns but the virus is transmitted in air. Please consult CDC and see this as a prototype for making homemade masks.

Step 1: Mask Base

The corner of the milk jug is nearly exactly the shape of a traditional mask. After cutting out the shape I used a pliers to dunk the mask in boiling water. I was then able to add some contours to nearly match my face.

Step 2: Cartridge Connections

Cutting out the holes...

Trace the outside screw end of the cap.
Slightly oversized is OK.
Use silicone sealant around the cap once in place. Best to rough up the plastic first with sandpaper. To de-burr and allow for a better connection with silicone.

--you can see that I used a layer of electrical tape

Step 3: Foam Edging

The foam allows for the flexible fit.

Staples help pinch the corners if the plastic isn't perfectly shaped. I'd likely make a slit and overlap the corners if I was making this one again.... The duct tape will ultimately cover any slice in the plastic.

Next step we'll hem the foam in place with duct tape.

Step 4: Vent -v1... Fail

Have a look for reference. I like this design but it really needs a flexible rubber piece to create a vent... not the plastic I used from the milk jug.

----see version 2 in next step

Step 5: Vent Success

This vent is outstanding. Very simple and efficient.

Drill holes in the size of the cylinder tube.
Secure a plastic glove... or other plastic material that stretches over the holes.

---air exits the vent but can't enter back into the mask.

Key Feature. It doesn't protect others from your exhale but means that the environment inside the mask is much more comfortable because the humid air that's exhaled doesn't go back through the filter material.

Step 6: Filter

Here you can see my simplistic approach to the filter...

Drill holes
Secure filter material with elastic
Here I used two layers of a cotton shirt. This doesn't meet the recommended standards of anyone but is starting to be used more and more. A better option is to cut up filtered material rated to a sufficient standard. See my note in the materials section about following CDC recommendations --again this is a prototype to help advance the conversation around mask design.

Step 7: Final Thoughts

Thank you!

If you made it this far I appreciate your reading. I hope this has you thinking of ways to advance mask design. It certainly has for me. I've worked through two prototypes since and continued to work on what I think are the critical components:

Connection to Face
Filtration
Cartridge System

Would love to discuss further with anyone else who's experience in injection molding. I see this as by far the best option to scale a solution to the global mask shortage. They can be produced at 1/second a single machine compared to 3D printing at a rate of 1/hour.

Cheers! Jeff

--this is important to me. All of my family works in the healthcare space. Social distancing is critical and the best way to help protect the ones we love.