photohiker wrote:Ok. Seems we should have them outside our home. Can see a lot of them on eBay do you have any idea which be good. See some are available in AU.
Both to GadgeGeek and above, sorry for the delay in this reply.
Just for a bit of background. Infection control is as for pandemic response, it's the additive effect of each of the item and procedure that provides a water tight (or close to water tight) defence against the agent. As such, mask alone (through SARS experience) provided 68% effectiveness while hand washing alone provided 54% effectiveness. Combining both, 92% effectiveness could be achieved. So on a similar idea, the more one does the better the result, but obviously within reason. For masks, something is better than nothing. Even with mask, don't short change on hand washing and social distancing!
In terms of commercial mask choices, there are 3 major categories.
1) Unrated 3 layer: These are commonly used on cosmetic stands. Thin and don't have proper spec and rating, though they usually have non-woven fabric as the middle layer. The so called 3 layer refers to an outer layer that has some level of water repellency, middle layer non-woven and an inner layer that has some absorbency for moisture in our breaths. As they aren't specifically spec'ed, so there'll some variation in quality. But sometimes they can be pretty close to proper medical masks, just the factory wasn't certified. They are readily available on eBay and elsewhere by mail order. Last I saw they can be had for around $50/box of 50. Some chemist and other walk-in stores also sell these for more.
2) Medical grade: These masks are what most would recommend for community use. Within these, there are 3 ASTM levels 1, 2 and 3 with 3 being the highest rated. Any of these are more than good enough for community use as they are properly rated for filtration efficiency and blood/fluid resistance. Level 3 is what's used for surgery where the user is better protected from blood or other fluid spurts, hence the highest rating within this group.
3) N95/P2 mask: These are typically called respirators for they have even higher specs for seal and filtration, down to PM2.5 as is needed during our bushfire/smog period. Medical personnels use these for close range COVID-19 patient contacts as they offer reliable protection and in particular against aerosols. These don't filter virus (virus don't have legs or wings) but filter down to the tiny aerosol sized droplets those virus can travel in. Aerosols are not generated by regular speech or coughs but typically through machineries eg. Dental drills and other medical equipments.
As suggested, ideally in community that people should have at least a basic ASTM Level 1 mask as the main mode of transmission is by large droplet respiratory spread. These are more than good enough for both protecting self from others as well as for protecting others if self is infectious, though then N95/P2 would be even better to ensure there's a better seal. But given our current shortage of masks for the healthcare workers, those unrated 3 layers masks should be the conscience buy as hospitals don't want them. For community use, these are far better than nothing and is a fair compromise. Should one not have any of these, various home made solutions, even down to a layered silk/woollen scarf can be better than nothing for protection, just make sure they are clean.
Now on the question of mask cleanliness. Yes, these masks are designed for single use but in practice and for community use, I use them at least a few times (eg. Shopping centre, public transport) before replacement, as long as they are kept clean and have not been used in a high risk area. What's important is how it's used and stored. Treat the outer and inner surfaces to be separate compartments and should not be touched. Putting on and off the mask by holding the ear loops than the actual mask itself. When away from people, I would take it off and lay it on a dry and clean piece of paper. Remember also, coronavirus will disintegrate by itself over time, though varies by the material it's on. Leaving it well aerated would also clear the moisture after each use. Pick it up by the ear loops again at next use.