I’ve looked at a small amount of data on this question. I think it’s a really important one (see a related question of mine), but am extremely not an expert. The most actionable item is this study that essentially “salting” a surgical mask might make it significantly more protective against flu viruses. The study’s in vivo section with mice strikes me as a bit sketchy (small n, and unclear how representative of mask filtration their mouse procdeure actually is), but their in vitro section seems legit, and the study is in Scientific Reports (part of the Nature publishing group). If you’re making a DIY mask/filter and it’s not too thick already, it can’t hurt to include a salted layer. Their proposed mechanism of action is by the salt killing the virus particles, not filtering them, so it should stack well with particulate filters. The recipe in the paper is to coat a hydrophobic filter in solution of salt and surfactant (they used polysorbate 20, which is approved to use as a food additive), then let it dry.
The 100% efficacy for a middle filter layer that’s had a saltwater + surfactant sprayed onto it sounds really good; but I wonder how tight the filter material has to be, for that level of efficacy. I also wonder how much air resistance the salt coat adds.
A HEPA filter + carbon would be less restrictive if the carbon part were salted than if the HEPA filter itself were salted, but that might not deactivate all of the virus.
Not sure but doubt it: IIRC, copper kills by catalysing intra-cellular reactions, which are slow (compared to salt, which should have near-instantaneous mechanism of action since it can blow up membranes). Also I would be worried about safety of breathing copper. But I might be wrong about this!
I’ve looked at a small amount of data on this question. I think it’s a really important one (see a related question of mine), but am extremely not an expert. The most actionable item is this study that essentially “salting” a surgical mask might make it significantly more protective against flu viruses. The study’s in vivo section with mice strikes me as a bit sketchy (small n, and unclear how representative of mask filtration their mouse procdeure actually is), but their in vitro section seems legit, and the study is in Scientific Reports (part of the Nature publishing group). If you’re making a DIY mask/filter and it’s not too thick already, it can’t hurt to include a salted layer. Their proposed mechanism of action is by the salt killing the virus particles, not filtering them, so it should stack well with particulate filters. The recipe in the paper is to coat a hydrophobic filter in solution of salt and surfactant (they used polysorbate 20, which is approved to use as a food additive), then let it dry.
The 100% efficacy for a middle filter layer that’s had a saltwater + surfactant sprayed onto it sounds really good; but I wonder how tight the filter material has to be, for that level of efficacy. I also wonder how much air resistance the salt coat adds.
A HEPA filter + carbon would be less restrictive if the carbon part were salted than if the HEPA filter itself were salted, but that might not deactivate all of the virus.
Would “salting” with zinc or copper help too?
Not sure but doubt it: IIRC, copper kills by catalysing intra-cellular reactions, which are slow (compared to salt, which should have near-instantaneous mechanism of action since it can blow up membranes). Also I would be worried about safety of breathing copper. But I might be wrong about this!