Face Masks

Design Considerations.

All masks need to be evaluated for how well they seal around the edges.

Pulling a section of panty-hose over a mask can pull all edges firmly against the wear's face.

Getting a seal around the nose is a major design problem, and every face is different.

Commercially available ear-loop masks are problematical. Here is one useful device you can make:
Loop Grabber

Designation Considerations

If you can get any of these they should work for you. Apparently some regulation prohibits US medical personnel from using any but the N95 kind.

FFP2 (Europe EN 149-2001)
N95 (United States NIOSH-42CFR84)
DS2 (Japan JMHLW-Notification 214, 2018)
KN95 (China GB2626-2006)

Fabric Considerations

The best choice seems to be Filti non-woven nanofiber fabric  (MERV 16) as a center layer, an inner layer of comfortable and absorbent fabric, and an outer layer of a durable fabric that can serve as a pre-filter. (See test results.)
There is a 3M "hammock style" blanket filter that is MERV 11. Filtrete MPR 1500 MERV 12 filters are available, but they are bonded between sheets of expanded metal.

Linked from Smartairfilters.com.  If they replace these graphics, you may need to go to the original source.

My Own Mask Design
I use a variety of materials. Both 40 denier nylon and 0.33 or 0.50 pound per square yard cotton material suitable for kitchen towels or for making quilts would be suitable for the outside layers. The center consists of an approximately 4 inch by 6 inch piece of nanofiber unwoven fabric for the high-quality filter. There is a drawstring at the bottom that adjusts the mask's fit at the neck, and an elastic strap that goes up and back over the head.  See the pattern and details here.



1 mm canvas is 18 oz per square yard, also identified as number 8 cotton duck

1 mm canvas is 18 oz per square yard, also identified as number 8 cotton duck

Business Insider Evaluations

The most practicable way to evaluate mask materials at home is to see how much light makes it through a fabric in a straight-line (peep hole). See my microscopic examinations of several types of fabric.

RAW EVALUATIONS (from the Business Insider study linked above)
1 layer Filti+ 1 layer 6.5g Cotton Rip Stop 84.03 13.33
2 layers Kona 100% Cotton + 1 layer 1500 Filtrete Furnace Filter 80.85 8.15
2 layer Kona 100% Cotton + 99.7% Vacuum bag lining (no paper) + 1 layer Swiffer Dry Sheet 68.48 10.82
1 layer Evolon 100g 57.56 11.2 1 layer Zep Towel + 1 layer Radnor LW Oil Absorbent pad 66.49 11.44
1 layer Zep towel + 1 Layer Toolbox towel 55.66 11.57
2 layers 100% Bamboo Rayon + 2 layer Swiffer Dry Sheets 44.77 14.72
2 layer Toolbox Shop Towels 41.94 11.98
2 layer Hanes 100% Cotton knit + 1 layer Zep Towel 39.08 11.54
2 layer Bandana + 1 layer craft felt + 1 layer Toolbox Shop Towel 36 9.78
1 layer Uline Lightweight Old Absorbent Pad (not dimpled) 35.02 2.67
2 layer Wypall towels x80 30.58 6.1
2 layer Viva Classic Towel + 1 layer Swiffer Dry Sheet 30.01 2.16
3 layer Hanes 100% Cotton T-shirt 27.98 8.88
4 layer Viva Classic Paper Towels 22.54 3.37
2 layer Pellon Med.Weight Fusable Interfacing 17.24 1.08
1 layer Kona 100% Cotton + 1 layer Flannel 15.39 8.08
2 layers Braun Coffee Filter 14.1 16.42
Folded Bandana 9.65 3.38
2 layers Kona 100% Quilters Cotton 7.02 6.49

SCALED EVALUATIONS CONSIDERING BREATHABILITY

2 layers Kona 100% Cotton + 1 layer 1500 Filtrete Furnace Filter 72.7
1 layer Filti+ 1 layer 6.5g Cotton Rip Stop 70.7
2 layer Kona 100% Cotton + 99.7% Vacuum bag lining (no paper) + 1 layer Swiffer Dry Sheet 57.66
1 layer Zep Towel + 1 layer Radnor LW Oil Absorbant pad 55.05
1 layer Evolon 100g 46.36 1 layer Zep towel + 1 Layer Toolbox towel 44.09
1 layer Uline Lightweight Old Absorbant Pad (not dimpled) 32.35 2 layers 100% Bamboo Rayon + 2 layer Swiffer Dry Sheets 30.05
2 layer Toolbox Shop Towels 29.96 2 layer Viva Classic Towel + 1 layer Swiffer Dry Sheet 27.85
2 layer Hanes 100% Cotton knit + 1 layer Zep Towel 27.54 2 layer Bandana + 1 layer craft felt + 1 layer Toolbox Shop Towel 26.22
2 layer Wypall towels x80 24.48 4 layer Viva Classic Paper Towels 19.17
3 layer Hanes 100% Cotton T-shirt 19.1
2 layer Pellon Med.Weight Fusable Interfacing 16.16
1 layer Kona 100% Cotton + 1 layer Flannel 7.31
Folded Bandana 6.27
2 layers Kona 100% Quilters Cotton 0.53
2 layers Braun Coffee Filter -2.32

Disinfecting Masks
Rotation
0.1 Store in warm, dry place for at least 72 hours.
Boiling or Steaming
0.2 Submerge mask in 125°C (260° F) steam or in boiling water for 3 minutes. Do not excessively stir mask, just manipulate it enough to keep it fully submerged. Paper will not survive this treatment.

Baking
0.3 Put a dutch oven or a covered roaster pan in your oven. Preheat to 70°C (160°F). Place mask into the covered container, return to oven, and cook for 30 minutes.
Source of the above methods https://ipsnews.net/business/2020/04/09/how-to-clean-and-reuse-an-n95-mask/

Microwave Steaming
Fill a bottle (something like a mayo bottle) about halfway full of water. Turn your mask inside-out. Place it over the mouth of the bottle. Microwave it for one minute. Turn the mask rightside-out. Place back over the bottle, and zap for another minte.  Warning: Failure to put water in with anything dry that is put into a microwave over will result in a fire. A piece of bread can be warmed in a microwave, but if all its water steams away you will end up with smoke in your kitchen and charcoal in your microwave oven. See: https://www.webmd.com/lung/news/20200709/study-sterilize-n95-masks-with-a-microwave

Knowledge base:
Do masks starve us of oxygen?
Are Polypropylene Bags Effective as DIY Face Masks for COVID-19  2020-06-10
Can HEPA Filteres Be Used to Make DIY Face Masks?  2020-05-13
What Are HEPA Filters and How Do They Work? 2020-05-07  Very good discussion of why N95 filters are perfect for filtering viruses.
The Ultimate Guide to Homemade Face Masks for Coronavirus  2020-04-21
Does Microwaving Masks Disinfect Viruses? 2020-04-03    NB This report neglects to mention it's necessary to put a half cup of water in with the mask to avoid the danger of fire.
Is Washing Masks Effective After Virus Exposure?  2020-03-18
Are Paper Towel Masks Effective at Blocking Viruses?  2020-03-08
What Are the Best Materials for DIY Masks?  2020-03-08
Can DIY Masks Protect Us From Coronavirus  2020-03-04
How Long Do N95 Masks Last? 2019-11-11
Will the Moisture Cause Fungal Spores to Grow in My Mask, So They Should Be Thrown Out Every 1-2 Days? 


How to clean and/or sanitize masks

How microwaves work to destroy the integrity of virions:
Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials
https://ntrs.nasa.gov/search.jsp?R=20170005166

Practical applications:
Microwave or Autoclave Treatments Destroy the Infectivity of Infectious Bronchitis Virus and Avian Pneumovirus but Allow Detection by Reverse Transcriptase-Polymerase Chain Reaction.
https://pubmed.ncbi.nlm.nih.gov/15223557/

Microwave Sterilization
“This study has shown that representative fungi, viruses, and aerobic and anaerobic bacteria, including spore formers, can easily be killed in a conventional microwave oven with proper modifications.”
https://pubmed.ncbi.nlm.nih.gov/3884686/
"An Air Force report from 2012 shows how to sterilize N95 masks using hot steam from microwave and standrd ovens, as well ultraviolet germicidal irradiation (UVGI) light bulbs. The success rate was 93 percent with all three methods.
https://www.enviroreporter.com/2020/04/n95-masks-safely-sterilized-in-microwave-ovens-after-two-minutes-with-93-success-rate-says-2012-air-force-report/
https://mbio.asm.org/content/11/3/e00997-20

Heat
https://iheartintelligence.com/stanford-researchers-n95-masks-sterilized-reused-low-temperature-heating/






































































Major Considerations

Evaluations of Fabrics



Section 2



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This page was last revised on 8 January 2021.