Mass producing surgeons masks

The purpose of this project is to demonstrate an optimal method for how to produce up to 20 masks per hour of Consistent quality, with a tight fit and performance equal to a high quality surgeons mask. It is made from commonly available materials and requires marginal skills.

WHY PRODUCE SO MANY?
You need a number of masks so you can rotate them. (By quarantining worn masks for at least a week before re-using). Then, masks will need to be replaced when getting dirty, lost, worn out.. Then, those you care for need masks.. Then, they need to rotate and replace..

FILTER RATING VS. DESIGN
The mask presented here is assumed as effective, in terms of filtration ability, as any high quality Surgeons Masks. I read the report from Cambridge University (ref, p2) as HEPA rated vacuum bags are optimal for making surgeons masks given a) you find, unlike them, a hepa material that allows enough air through and b) it, unlike theirs, is well designed (providing a tight fit).

Why the surgical mask design? They are effective, quick and easy to make. By numbers the FFP2/FFP3 (N95/N99) are superior to Surgeons Masks (ref) but in reality, the gain in terms of ability to keep you safe seems somewhat marginal (ref, Closing statement / Comments: " In routine health care settings, particularly where the availability of N95 respirators is limited, surgical masks appear to be noninferior to N95 respirators for protecting health care workers against influenza.")
The question is therefore - Should you attempt making a limited number of FFP2 equivalent masks, or a sufficient quantity of high quality surgeons masks?

Why not a mask with a hepa pad/pocket? There are several issues with this type of design. Most importantly, a portion of the inhaled air would bypass the pad and enter through surrounding material. The entire mask must be made from Hepa filter material to minimize false entry. Also, a hepa filter is 'tuff to breathe through. The smaller the pad the harder it is to breathe. Hence the pad should be as large as possible. Ie. again, the entire mask should be made out of hepa material. Then, contamination.. You can not repeatedly wear the same mask. Masks must be sterilized after each use, or they must rest for a week before re-use. It isn't enough just replacing the pad. A semi disposable surgical mask is as I see it the only viable route.

Research shows masks do not protect children well (ref to be added). Many factors come to play here, but the most obvious thing we can do about it is to provide the children with comfortable masks that fit them well. A mask adapted to children 5-12 is therefore available below.

SOURCING A SUITABLE MATERIAL
Our choice of filter fabric is the "Numatic Hepaflo" vacuum bag. It consists of 3 layers of SMS (spun-melt-spun) Polypropylene/PP, just like the material used in most surgical masks. Its technical documentation indicates an ability to stop 80% of dry 0.3 Micron particles - i.e. it is a H10 class HEPA filter, equivalent (if not identical) to the filtering ability of the highest quality surgeons masks. The fabric is neat and thin and easy to work with. You can of course use other hepa rated vacuum bags from other brands. In addition, there are other fabrics you can use, Cotton, tea towels. Please have a look at a few options (Table 1). Unfortunately, most alternatives are inferior to a H10 or upwards HEPA material.

NB! Paper quality bags are NOT suitable for this project.

Dry dust filtering ability is graded in classes (ref):
G (G1-G4),M (M5-M6) and F (F7-F9) class are not suitable for this project.
H10 (EPA or 'Semi HEPA' E10) is ~FFP1 equivalent and optimal for this project.
H11 and H12 (EPA or 'Semi HEPA' E11/E12) are ~FFP2/N95 equivalent may be usable but please test for sufficient airflow as suggested below.
H13 and H14 (>99,9% @0.3micron are true HEPA and comparable to FFP3/N99/N100) Airflow likely too restricted for this project.
U15-U17 (ULPA) Ultra high filtering ability but again, airflow is insufficient.

The best balance between filtering ability and avoiding issues with airflow seems to be found at about >= H10(E10) and <=H11(E11).

Testing airflow. To test your material for sufficient airflow: Breathe calmly and exclusively through a fabric sample with your mouth wide open while walking at a slow pace up and down a stairway a few times. Keep breathing exclusively through the fabric until your heart rate is back to 'idle. If you can resist the urge to have a fresh whiff of air then there is sufficient airflow. (Airflow will be improved through the proportionally larger fabric used in the finished mask)

If the filter material you've obtained failed 'the test' - consider 'A Doctor Explains How to..' found in the links below. Their design allows the use of materials with reduced airflow. It is a very good option if Quantity is not of your concern.

Also I - Safety: Avoid products labelled 'odourless', 'odour control' etc. Chemicals and possibly perfume have been added to absorb smell and/or trap moisture.

Also II - "Fibreglass..?": Unlike some HEPA filter cartridges used in ventilation, fabric vacuum filter bags are made from SMS PP/thermoplastics not fibreglass. You can easily test your material to be sure it is indeed a thermoplastic by simply setting fire to a little sample (over a fireproof surface please). Hold with pliers. If it burns and drips like candle wax and leaves no 'bush' of brittle fibres behind, then you know it is indeed a thermoplastic. Alternatively, try this method..

Also III - Airflow/direction: A vacuum bags inmost layer is a course filter, the middle layers are the finer filters. The bags outer layer just prevents the bag from ripping. Therefore, the bags inmost layer should if possible face outwards when worn as a mask.

STERILIZING
Preheat your oven to 70 deg Celsius (that's 158F). Use an oven thermometer! Make sure the temperature has stabilized before proceeding. Seal masks individually or in batches in air tight (zip lock) plastic bags. Wrap the zip lock bags inside a few kitchen towels to protect them from direct radiation from the ovens heating elements - and bake in a tray in the low/middle for an hour. NB! Do not use the hot air/fan function.

#The Stanford report states a home oven should not be used for re-sterilization of used masks due to the risk of bringing contaminaton home. There should be no reason why a home oven cannot be used to sterilize masks produced by yourself. (ref, p2)

#Zip lock bags: Any size from 11x18CM (4.5"x 7") and up. Alternatively, use freezer bags (tie a knot to seal..)

PERSONAL REMARK To sum it up ..? I use this mask myself every day. So does my 2 kids and my wife. In the shops and around town. (As a bonus it also really helps against pollen allergies.) Though, a surgical mask may not the best choice for situations where people literally sit on your lap, like when flying. I will be making myself a handful of these if forced to travel.

CORRECT USE..
- Wash your hands before putting on or removing your mask. Wash once again after the mask is removed. Never touch your face (or mask) while wearing a mask.
- Do not put a recently worn mask back on. Make yourself a number of masks, rotate and let them rest 1 week before re-use.
- Walk slowly, breathe calmly. Keep your distance. Take your time....

PLEASE HELP HELPING
Please share the link to this page
Or use this link if you wish to link directly to the video on Youtube.

With Love from
St Esteve de Palautordera
Spain

Stian Haugli
Industrial Designer MA
Please click here for email
+34 622 13 7743
+47 46 298 131


REVISION HISTORY
20201019 - Touch'up..
20200517 - Updated templates will be uploaded soon. Minor changes.
20200429 - Added the how-to video
20200425 - Children's mask improved
20200423 - Edited the Youtube video
20200414 - Valuable feedback and user testing. Thanks Axel.
20200413 - Installed Matomo
20200412 - Mask for children 5-12 YRS published. Added note re. fibreglass and to avoid "odourless" bags.
20200411 - Rewrite and typos
20200410 - Published for initial review
20200408 - 1st Draft

REFERENCES

Numatic Hepaflo datasheet (or here)

HEPA / Filter classification, Wikipedia

Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers

Particle Size-Selective Assessment of Protection of European Standard FFP Respirators and Surgical Masks against Particles-Tested with Human Subjects

Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic? |

Disaster Medicine and Public Health Preparedness | Cambridge Core

N95 vs FFP3 & FFP2 masks - what's the difference?

A Doctor Explains How to Make the Safest Face Mask - YouTube

https://stanfordmedicine.app.box.com/v/covid19-PPE-1-1

Fibreglass in vacuum bags?


TODO
- The smaller size will be posted soon. (Please scale the Regular size mask down for now. print at ~90 %)
- A tips and tricks / FAQ section may be needed..
- Lab testing. Can "someone with a lab" please come forward and offer to do a head to head comparison of our design to a standard surgeons mask. An independent test will provide hospitals, schools etc around the world with the evidence and courage they need to produce this mask. please contact me

WHY are you doing this?
Quite some effort went into research, development and prototyping. I documented the process for family and friends to be able to replicate while we wait for amazon to stock back up.. It made little sense not to share, so here it is, with the best intentions, on the house :-)

DISCLAIMER - All content linked or published on this webpage is designed and developed by the owners of this website. No content should be copied, kept or distributed from elsewhere without our consent. Please respect intellectual property. This project is under constant and rapid development - changes made here can contain vital updates important to people and their health. Please link to this page instead of directly to what may be outdated content on this page. Hypothetical revenue generated from the youtube content, if any, will be donated to local healthcare. Profit is not the drive here.

GDPR - Youtube drops a 'doubleclick' cookie on you because of the embedded video. This page also writes a cookie (Matomo Open Source Analytics). I collect out of curiosity statistics to know where visitors connect from. Personal data are anonymized when collected and stored anonymized in our database. It will be interesting to see which parts of the world makes use of this. The stat data are kept locally and will never be shared. All stats will be flushed once this project is no longer required (thank you for understanding)

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