NOTE: This mask is designed as a stopgap respirator – it is not certified to any existing standard. With cotton makeup pads it at best can be expected to perform similarly to a surgical mask (this has not been confirmed in a lab, however).
Without melt-blown fabric it cannot filter to the same level as an N95 mask and even with the material it has only passed a basic fit check.
This respirator is based on research (1, 2, 3) showing that cotton can be a relatively effective filter for stopping B Atrophaeus, bacteria that is roughly 1 nm in length (Source). A double-layered, thick-woven tea towel had similar filtration capacity as a standard surgical mask (96%), and even a double-layered cotton T-shirt had 70% capacity.
The respirator is not provided with any promises of protection against COVID-19. You use it at your own risk.
It currently uses Target-brand double layer makeup pads as a filter. However, these filters can be swapped out with cut-up N95 masks or other filters.
The respirator is currently on version 2.0 – adding a second air valve due to feedback from medical personnel to make it easier to breathe through. The image below shows the original v1 design being worn.
You can find the Original Onshape CAD document here. I am releasing this file as open source, provided changes are credited and the design is not sold. Full license at the end of this page.
3/27/2020: Added link for v2.1. Changelog: Reduced diameter of filter cartridge breathing holes to ensure they are more tightly secured.
4/7/2020: Version 3 uploaded with small/medium/large sizes and print ease improvements.
4/15/2020: Version 3.1 uploaded with extra small, extra large sizes. Additional tweaks to retain nose pinch bracket on all sizes. Breathing holes slightly increased.
Layer height: As big as possible. Good results with .3mm and decent results with .6mm have been tested.
Average print time @ .3mm: 2 hours / 1 hour @ .6mm.
Print in a face-down orientation.
Required Materials & Tools
- TPU filament.
- Dual-sided cotton makeup rounds. The ones I designed for are from Target are 54mm/2″ in diameter.
- Rubber bands (medium sized).
- Electrical tape.
- Paper clip.
- [Optional] 100% pure silicone caulking. Lots of this in stock at Home Depot.
- Self adhesive D-shaped weatherstripping, around 7/20″ or 9mm (like this or this). This can probably be substituted with thin foam if necessary.
- Needlenose pliers.
- Foam tipped brush.
Pictures to come soon.
- Remove respirator from build plate and clean off any excess stringing.
- Starting from the bottom of the mask, install the weather stripping by carefully laying it along the inner edge.
- You do not need to line the inner sides of the filter housing.
- Once you’re near the end, cut it just a few mm long, then jam that edge up against the opposite side of the liner. This will help it form a better seal and stay in place.
- Cut a roughly 50mm/2″ length of paper clip and insert it into the nose bridge. Note that this might be a little difficult – work it in there with the pliers.
- [Optional – only if your fit check shows air gaps] Squirt a bit of silicone onto the respirator and then brush it liberally across the surface using the felt tipped brush. The silicone will close any airgaps and make the mask watertight. Make sure you cover the entire outside.
- Wait at least 30-45 minutes for the silicone to cure.
- Insert the rubber bands through the loop holes. Pull one end through, then pull one end of the rubber band through the other, forming a knot. Do this for all four loop holes.
- Next, cut two strips of electrical tape roughly roughly 6″/155mm in length.
- Lay it flat on the table, sticky side up.
- Put a paperclip on either end of the tape.
- Lay the second piece of tape on top of the first one, sticky side down. The paperclips will keep the ends from sticking to one another.
- Remove the paperclip and wrap the bottom half of the tape around the rubber band.
- Wrap the top half of the tape around the rubber band and other half of the electrical tape.
- Repeat the same for the other side of the mask.
- Known point for improvement: The rubberbands can be uncomfortable for long-haired people when donning and doffing the mask.
- Duplicate the previous step for the next pair of rubber bands.
- Insert the filters into the slots in the back of the mask.
- Spin them clockwise or counterclockwise.
- Once part of them peeks out in the hole, grab it with your fingertips and pull it forward, then push it into the front groove of the cartridge.
- To put the mask on, first put the bottom strap over your head and around the back of your neck. Then pull the top strap over the back of your head. The mask should fit underneath your chin. Squeeze the nose bridge to press it against your nose.
Sanitation & Safety
- The electrical tape that makes up the strap of the mask has a lot of folds in it. Until a better alternative is found, try using a single rubber band or clean the tape thoroughly.
- Cotton filters are only as effective as a surgical mask. They do not completely stop the virus.
- Ideally the mask should be submerged in IPA and the fluid to enter into all the cracks and pores of the mask, then pulled out and left to dry for 30 seconds. At minimum, the mask should be wiped down after every use with 70%+ IPA “rubbing alcohol”. This will kill COVID-19 that will accumulate on the outside of the mask. See chart below:
Copyright (c) <2020> <Jordan Elevons>
Permission is hereby granted, free of charge, to any person obtaining a copy
of this design and associated documentation files (the “Design”), to deal
in the Design without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, and to permit persons to whom the Design is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Design. Digital or physical copies of the design cannot be sold without express permission from the copyright holder. Modifications to the design must credit its original source (Jordan Elevons).
THE DESIGN IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE DESIGN OR THE USE OR OTHER DEALINGS IN THE DESIGN.