Introduction: ÊPA - Covid-19 Safe Face Mask-Now Updated
This tutorial on a face protection mask was developed based on research by the group of Brazilian volunteers called DESIGN ANTIVIRUS, dedicated to bringing emergency solutions to combat the covid-19 pandemic.
According to several scientific articles on the subject of facial protection masks, whether homemade or professional, it was possible to identify three main characteristics that leave a safe mask for use as protection against virus contamination:
1- Filtering capacity and virus / physical barrier retention..
It relates to preventing the virus from entering the respiratory tract (mouth and nose) and eyes. As already documented, the virus alone is not capable of infecting a person but hundreds of millions of viruses. The virus has the best vehicle for this, the micro and macro droplets that are released into the environment by infected people, whether they have the symptoms or not.
The macro droplets (Droplets >5 µm), which are heavier, quickly descend to the ground, and have little reach (no more than 1.m-2 m). However,the micro droplets or aerosols (Droplets<5µm) are suspended longer in the air and especially indoors.
2-Effect of gaps between the contour of the face and the mask.
This as caused by an improper fit will affect the efficiency of any mask.This is of particular relevance to cloth and cirurgical mask that are used by the public and which are gennerally not fitted, unlike N95, PFF2 elastomeric reusable respirator.
3-Ease of asepsis and mask cleaning.
In general, fabric masks are easy to wash and aseptic. Surgical masks and N95 masks, on the other hand, were not designed to be used in a continuous manner different from elastomeric reusable respirators.
There are many studies on the Sterilization of N95 / PFF2 masks and also surgical masks that use TNT-SMS based filters. The known forms include leaving for an hour at a temperature of 70 degrees Celsius, use of hydrogen peroxide, use of UV-C and ozone. Remembering that the use of alcohol and other solvents removes the electrostatic charge from one of the layers.
About our ÊPA mask
With these three points in mind, we developed a PPE, which has a body of elastomeric material that adapts to different faces, creating an efficient seal. The mask uses filters that can be easily washed or replaced and the mask is adjustable for better comfort and efficiency. But all this using materials already on the market, without the need to create any new special piece.
Now we've updated the design and we have three different sizes. A new video showing its construction can be seen here:
- One piece of 15cm x 25cm , 2mm sheet of E.V.A. foam or Fabric-Covered Multipurpose Neoprene Foam
-1 piece of a 1,5mm bare conductors inside the jacket - 8mm long
- Two Curtain eyelets with an internal diameter of approximately 40 mm and an external diameter of 60 mm.
- One elastic band 9mm wide or 3mm rope - 90cm -100cm long
-One lace Lock
For the filter material
It is possible to assemble with both dry and wet type filter sets.
In the dry filter, hydrophobic materials are used and in the wet filters hydrophilic materials. When using hydrophobic filters such as TNT SMS or Polyester or Polypropylene TNT, the humidity inside the mask will limit the time of use, for this we created the solution of using an absorbent bag containing table salt or non-toxic silica gel in the form of pellets of orange color, which changes to green as it becomes saturated with moisture.
-One sheet of Duramax Kitchen Towel( cellulose 70% ,30% polypropylene) Hidrophilic.
-One 3M Filtrete Anti Pollution Filter( made of polypropylene) or Kitchen Exhaust Fan Filter ( 100% polyester) or HEPA filter made of made of polypropylene, hidrophobic.
It is possible to assemble with sets of fabric filters, called wet filters used in handmade masks.
When we use hydrophobic filters, we use a hydrophilic filter inside to help absorb moisture from inside the mask, as well as placing an external filter to create a barrier for macro droplets.
-One instant multipurpose adhesive type Tek Bond 725, Loctite's "Flexible Adhesive,
Stylus, cutting pliers, knife, scissors.
Make sure the materials are clean, sanitize your work area and wash your hands with soap and water before you start. IMPORTANT: These masks contain industrial materials and can be made in industrial processes more easily.
Step 1: Technical Drawing, Templates, Cutting , Marking Position.
Download the mask design in PDF to create the templates to cut and position the pieces to paste and fold.
Use the design of the open mask printed on cardboard or paper to cut the model. Another option would be to use the file directly to cut a mold made of a more durable contour material, such as a 5 mm MDF board to facilitate cutting with a hobby knife. The quickest would be to cut the elastomeric material directly using a laser or a Silhouette cutting machine similar. But we do not recommend cutting neoprene on the laser as it generates highly toxic gases.
Step 2: Gluing the Parts
Now that you have everything cut, let's stick the parts together. Start with the rigid wire that will be used to adjust the seal around the nose. Take the 8 cm long rigid electric wire and stick it centered in the area indicated in the technical drawing, which you marked earlier. Then glue the layer of material to protect and hold it firmly in place by spreading glue over the wire and around. Use a wooden board to keep the set pressed when the glue dries for about 30 seconds. Be careful that no glue has left the layer, as it may end up gluing the wood you used to press the set. Observe the side flaps that will be glued to form the cavity where the elastics will pass, remember that there must be enough space for them to run freely.
Step 3: Closing the Mask
There are two possibilities at this stage:
Either you already glue and close the mask by the central edge, or first mount the eyelets with the filters to then close the mask .
To help with this final bonding, I recommend folding the piece in half using a fat pen or tube on the nose clip. You can support one side on a surface of material not adhering to glue.Slowly place the glue along the area to be glued and press everything tightly using your fingers or use several paper clamps.
Now place the mask reinforcement located where the chin and the sachet holder(optional) will be.
Step 4: Putting the Filters on the Eyelets Attached to the Mask.
Putting the filters on the eyelets attached to the mask.
There are two ways to place the filters, in one the filters are outside and in the other they are inside.
First the male eyelets fit into the mask holes, then the 2-3 filters are stacked and placed over the female eyelets. Holding the set , it is positioned on the male eyelets centrally and with both hands, force the female eyelets against the male eyelets until you hear the fastening click.
Step 5: Placing the Elastic and a Lace Lock As a Regulator
You can use different types of rubber bands for this mask, we use rubber bands 9 mm wide or 3 mm of rope - 90 cm to 100 cm long. To help put on the elastic band, use a tapestry needle or other device that helps get the elastic through the flaps. The length of 90 to 100 cm will be more than sufficient, even when you choose to use a lace lock as a regulator.
Step 6: How to Make the Sachet to Increase the Use of Dry Filter Masks
This is an experimental part of this project and some options are possible.
As we said at the beginning of this tutorial, masks that use hydrophobic filters, have the problem of use limited by the mask's capacity to absorb internal moisture, especially when they cannot use exhaust valves.
1-Using moisture-absorbing material together with the filter. An internal layer made of TNT or fabric that absorbs the moisture that wants to leave can be accented, unfortunately this is limited by the absorption area and surface.
2- Use a highly absorbent material solid.The use of silica gel, and other salts are known, the oldest being table salt.The difference between them is the saturation capacity and toxicity. In our project we opted for dry table salt and silica gel that changes color to get an idea of the time for changing the sachet. We used large silica granules and for the sachet we used material permeable to moisture but not particles of these materials . So it was possible to have a safe and efficient way to solve the problem. After the sachet is saturated, just remove it and replace it with another one while drying the old one.
Step 7: How to Use, Adjust and Clean This Mask.
The Êpa mask, is a mask with 100% sealing made of washable rubber material . Contains 2 openings containing triple filters. Where the first barrier holds macro drops containing viruses, the second holds micro droplets containing viruses and the last has silver ions that kill 99.9% of the bacteria that may have passed through the first 2 barriers . Medical masks use TNT SMS filter plus an internal moisture absorber filter. These filters are washable and must be replaced as soon as they present external wear to the filter fibers. In general, when well taken care of, the filters last for 3 months and can be purchased separately. The asepsis of the mask and filters can be done by spraying 70 alcohol or 20 hydrogen peroxide . Another alternative is to wash with soap and water or 2.5% bleach solution in water (2 tablespoons of bleach to 1 liter of water) soak for 30 min after rinsing.
In masks for medical use, the body of the mask must be cleaned internally and externally with a gauze containing 70 alcohol. The filters must be asepsis by spraying hydrogen peroxide 10-20 volumes both on the outside and inside. Attention, do not use alcohol 70 for asepsis of TNT SMS filters.