We are not trying to be prescriptive about design choices. The functional requirements we propose are a starting point for discussion and will evolve.
At this early stage, it probably doesn’t make sense to specify any interoperability or performance standards. Clearly any product must perform better than existing equipment. Anyone investing in mass production should definitely take into account what standards are likely to be developed.
Time to mass manufacture is critical, so we have proposed aggressive timetables for products which don’t require any fundamental research. There is no reason why design for an ICU nurse and a bus driver or commuter should be different, they all need to work and uniformity is necessary for most efficient mass production. Nevertheless, although adjustable, there will probably need to be a couple of sizes.
The masks that are normally used by medics, KN95-FPP2-3, are basically particulate filter masks originally developed for dusty industrial applications and then more commonly used in Asia for protection against particulate pollution. The best basic face masks, which are quite difficult to breathe through and thus effectively often bypassed, are claimed to remove 99% of 300 µm particles. A dry virus is about 80 to 150 µm diameter. A bit of statistical maths suggests over 90% of virus will go straight through such a mask. Some virus may reside in larger drops of moisture before it evaporates in the air, and so a higher proportion of these may initially get trapped by the filter – but then as the moisture evaporates in the mask, what happens to the virus?
Similarly, the facemask, or the famous silk scarf, may significantly reduce the range of a moisture-laden sneeze or cough, but again – what happens to the virus if the scarf dries out?
Often, these poorly performing industrial filter masks are badly connected, if at all, to face shields or body suits. The eyes in particular remain extremely vulnerable.
There are many candidates for much more effective passive virus filters but all require assisted air flow.