Universal Mask concept with Seal

As applicable for all home brewed masks with a filtering purpose: this model is not tested by given standards, the functionality is not verified, and it’s not certified in any manner. Be aware of the risks and use it on behalf of your own responsibility.

All statements here are placed under best given knowledge, but are not proven to represent facts.

The use of these mask may be considered under emergency situations, if nothing more protective and for the purpose certified is available.

If there are professionals or makers with great ides out there, feel free to comment or criticize. Every input for improvement is valuable and welcome! If you have the ability to run some tests, be my guest, even if it destroys the concept of this mask.

-----Caution-----
The print quality can be critical to the desired functionality. Although it’s a bunch to read, please go through all the description and printing instructions before making those masks.
-----Caution-----

As we know, masks that are worn warm up by breath and body temperature. In addition, printed items offer a large surface area and gaps, where pathogens can survive well. Therefore, prevent to touch the mask once you wear it at potentially contaminated areas without cleaning and sanitizing your hands immediately afterwards. Consider repeated cleaning and sanitization cycles of your hands and the mask over time.

Breathing resistance:
The mask does not offer a too large filter area. It can be hard to breathe under a strong physical load. This can, to some degree, be compensated with deep, slow belly driven breathing. This breathing technology might need some practice. The construction restricts the airflow. It’s on purpose, to reduce the radius pathogens get spread, an get breathed in from.
For the sportive geeks out there: For a test I wore the mask at a bike based 1h sweet spot interval training. With controlled breathing my heart rate was about 10bpm higher than in a control test without the mask a few days later. As a filter medium I used a simple cotton pad. Probably not the best filter material, but eventually a representative breathing resistance. Be said: I’m not that well trained……and no, I did not pass out due to CO2 poisoning.
A version with doubled filter area is in consideration.

Talking:
As it’s a hard shell, some might feel uncomfortable. It needs time to get used to a restricted jaw movement and talking with it. You might have to talk louder to make the sound of your voice penetrate the filter and the deflector.

Filter Material:
Use the best filter material available for your purpose, and in emergency cases, filter materials that are suggested by authorized organizations. By the use of materials like cotton pads, cloths or similar, at least a reduction of spreading radius could be achieved.

Cleaning:
There are reports, that pathogens (i.e. Viruses) are reduced by a moist temperature treatment at 60°C for one hour, however reproduceable strains may be able to survive that procedure. Even if eventually not validated, it should be considered.

• I suggest to disassemble the mask and clean it in the dishwasher at 60°C for at least one hour. Add a detergent to interfere with the virus hull and reduce the contamination more efficiently. It’s also a matter of hygiene. Place the mask body with the outer face downwards, to avoid liquid restrains between the outer seal and the mask. The deflector should be placed with the inside facing downwards.
• It’s advised to dip all the parts in sanitizer, probably combine washing and sanitization.
  After cleaning and between the single steps, only touch the mask with washed/sanitized hands, and store it in a clean and protected environment (i.e. zipper bad). “Dirty” masks should be transported in a sealed manner as well, as they are a source of infection…. but never mix up the enclosures for the “clean” and “dirty” purposes!

Wearing:
The mask is designed to be worn with glasses, therefore the tip is not needed to be worn right between the eyes, although it can’t be excluded to be a good fit to someone. Consider the tip be rested in about the middle of the nose. If it won’t seal that way, move it more towards the tip of your nose or scale all parts. I encourage you to experiment the fit in a safe environment.
Once placed, cover up the outlet area (with deflector of) and inhale. The mask should be sucked towards your face. Be sure to have the straps tight enough, without resulting in unpleasant pressure points.
The mask should fit to a large variety of facial shapes as it is. Tests have shown that it’s kinda medium in size. Consider scaling all part to your needs.

Deflector:
The deflector is meant to guide the air downwards. Obstacles on which the air has to go around on, are to distribute the air evenly on the filter and avoid “hotspots”. Furthermore, it has the potential to capture inhaled droplets, as well as avoiding the wide spread of pathogens that are captured on the filter during sneezing, coughing or speaking. Do not use the mask without it!

Inner seal ring:
It’s there to push the filter material against the mask body, so that no air is able to bypass the filter. Furthermore, it protects the filter from being twisted during the application of the filter cap. Do not use the mask without it!

Outer seal:
It’s important that it’s applied and welded with care (see printing instructions). Make sure it sits well without leakage an is not damaged. It offers a stronger convex shape at the nose area, as this seemed the weak point in previous iterations. There are cutouts right behind the tip, to provide space for the nostrils if worn closer to the tip of the nose. It’s meant to contact the skin at the flat surface, not at the edges.

Coughing / sneezing:
It’s recommended to keep the habit, to cough and sneeze in your elbow. Use the armpit to push the mask towards your face, so that a sudden rise of pressure inside the mask doesn’t lead to leakage.

Print instructions

It is critical to close up as many gaps and air pockets as possible. On that behalf please stick to the following instructions:

• do not make the shell thinner. The perimeter loops are supposed to seal each other up
• at least 3 perimeters
• 100% infill only !
• first layer spot on, or a bit lower on purpose
• Flowrate set to a bit controlled overextrusion
• my tests have shown that it’s advised to print at maximum 60mm/s to receive sealed surfaces

Materials:
Use Materials that are capable of withstanding:

• 60°C without any deformation
• Isopropylic Alcohol
• Ethanol
• Water

Consider the use of materials with at least an FDA certification, better would be medical and for the outer seal skin contact certification. The Seal should be a soft/flexible material with max. 90 shore(A).
Materials that meet those standards are some PET-Gs and TPUs / TPEs. Read the technical datasheets and safety datasheets.

Deflector
It’s a snap on design. Depending on the print, it could be a bit tight. Scale it if necessary. Smoothing out the “snap on paths” with a soldering iron does the trick for me. This way it’s tighter than when being scaled.

Outer seal:
Activate the Z-Hop. If not, the lid could get pushed around after a travel move and you probably won’t achieve a nice surface finish.
It’s constructed to be printable on a flat surface without support. It provides two V-cuts, with some overlapping Material. They have to be welded together on both sides. A soldering iron with a clean flathead works pretty well. Smoothen out the inner side of the weld, to achieve a flat area for skin contact.
To apply the seal to the masks body, weld it on as well. Take your time for it and do it carefully. Start by tucking the tip of the nose. Then work towards the sides until after “valley”. Next tuck the center of the backside, then do the upper parts of the cheeks. Use clamps to ensure a continuous contact between seal and mask body. Be sure to leave no gaps, consider using a magnifying lens.
Be careful not to exceed the decomposition temperature of both materials, as this could lead to bubbles and unwanted pores.

Update 04/21/2020
Turns out the medium seal is a bit wide around the cheeks for some people. use the narrow version to achieve a little bit tighter fit.

If requested (and timewise possible) I could make a video of the seal application.

If help is wanted, feel free to ask questions !

Stay Safe!