Table 3.
Summary of typical components in a filtering facepiece respirator, important considerations in the selection or processing of material, and the final material or process employed for each component in Phase A or Phase B.
| Respirator Components | Considerations | Phase A (Sprint for MVP) | Phase B (Upscaling) |
|---|---|---|---|
| The filter material | The most crucial element of a respirator mask is the filter material, this material must be able to filter the virus. The material must be tested according to EN149. | PTFE nanofilter media for FFP2 or FFP3 classes. FFP2 media was in A4 sheet format. FFP2 media was on a roll | Same as Phase A |
| A protective layer | On the outside there should be a layer that protects the user from fluid spatter (blood, coughing). | Spunbond Polypropylene sheet (PP), 50 g. | Same as Phase A |
| A layer for comfort | On the inside of the mask there should be a layer against the skin for comfort and moisture absorption. | Spunbond Polypropylene sheet (PP), 30 g. | Same as Phase A |
| Welded edges | The edges of the masks should be attached together without perforating them. Regular sewing is not an option. | Ultrasonic cutting and point welding by hand. | Ultrasonic sewing machine, Cobot point weld, ultrasonic cutting by hand |
| Nose bridge | The nose bridge must be easy to bend but must be able to retain its shape afterwards. | Aluminum strip, 3.5 mm wide, 1.5 mm thick and 102 mm long. The thickness is crucial and will have to be adapted to the specific rigidity of your design. | Same as Phase A |
| Foam strip | Find a foam strip that is very soft. Chamfer its edges. | A Rolyan Low-Tack Polycushion Padding foam strip (latex free) with a hardness of 3 Shore A. 100 mm long, 20 mm wide and chamfered at 25 mm for the best fit to the face. | Same as Phase A |
| Head straps | The chosen head strap is a non-adjustable type made from elastic. Therefore the elastic band must have a good extension coefficient, to pull the mask firmly to the face. They should not lose their elasticity over time. Use non-latex materials or similar so the elastic bands do not slide of the back of the head. | Non-latex straps of polyisoprene were selected for this application. Width was fixed at 6 mm wide for optimal balance between strength, comfort and adaptability to various head sizes. | Same as Phase A |
| Strap attachment | The straps must be securely attached to the mask without perforating the mask. These attachments must be mechanically tested so they cannot come loose. | A Rapid 106E electric stapling machine was selected for this application. Type 66/6 staples were used, which created the necessary holding strength for the polyisoprene straps. | Same as Phase A |
| One-way valve (FFP3) | For most FFP3 masks, the filter material is difficult to breathe through. This could be dangerous for a multitude of reasons. Breathing out should be then facilitated with a one-way valve. | A new valve was designed and patented. It was designed specifically for 3D printing and rapid production. | Same as Phase A |