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N95 respirators, which are widely worn by health care workers treating patients with COVID-19 and are designed to be used only once, can be decontaminated effectively and used up to three times, according to research by UCLA scientists and colleagues.
An early-release version of their study has been published online, with the full study to appear in September in the journal Emerging Infectious Diseases.
[...] "Although N95 respirators are designed for just one use before disposal, in times of shortage, N95 respirators can be decontaminated and reused up to three times," said James Lloyd-Smith, a co-author of the study and a UCLA professor of ecology and evolutionary biology. "But the integrity of the respirator's fit and seal must be maintained."
[...] The masks treated with vaporized hydrogen peroxide experienced no failures, suggesting they potentially could be reused three times, Lloyd-Smith said. Those treated with ultraviolet light and dry heat began showing fit and seal problems after three decontaminations, suggesting these respirators potentially could be reused twice.
The study authors concluded that vaporized hydrogen peroxide was the most effective method because no traces of the virus could be detected after only a 10-minute treatment. They found that ultraviolet light and dry heat are also acceptable decontamination procedures, as long as the methods are applied for at least 60 minutes.
Journal Reference:
Robert J. Fischer, Dylan H. Morris, Neeltje van Doremalen, et al. Effectiveness of N95 Respirator Decontamination and Reuse against SARS-CoV-2 Virus, (DOI: 10.3201/eid2609.201524)
(Score: 2) by EETech1 on Wednesday September 02 2020, @07:47PM (3 children)
What makes it work is applying different charges to each layer of material.
How do you do that with a hairdryer?
Different nasties are attracted to different charge polarities, and some of them are neutral and have to pick up a charge by passing through one layer, and sticking to the next layer, or layers.
There's industrial hair dryers too, that use static the same way you describe, but they are not effective for this application. They are effective for charge neutralization. We use them to pull the surface charge off of the material that's formed when it's made so that it doesn't get attracted to the rollers in the machine, and end up wound around them. They are also used during conversion, IE taking a big roll, and making smaller ones to meet specific customer requirements. Unwinding the material generates a huge amount of static, but it is not useful in any way towards making the material actually work.
The actual structure of filter material is physically changed when it passes through the corona as well. This has to be done for the media to be effective. These structures do not last forever, and are the nooks and crannies that trap the particles that would normally pass right through. Every time the mask moves, some of these structures fracture, and loose their effectiveness forever, as well as letting go of whatever they have trapped in them.
At best you'd be applying a small surface charge to the outer layers, and they do not do the actual filtering for anything smaller than sawdust.
It's the inner layers that trap the very small particles like viruses and bacteria.
(Score: 1) by fakefuck39 on Thursday September 03 2020, @09:23AM (2 children)
This is false, as my organic chem and physics double minor from 20 years ago states. The virus is huge, on a molecular level. It has parts with positive and sides with negative charges. As long as you have the mask ionized, it will stick to it. Heck, a water molecule H+OH- has two charges. To test, you can line up a bunch of magnets all sticking out with +. Throw a magnet in there. It'll twist and turn, and it's negative part will stick to the + on the magnets you laid out. All you need on the mask is extra electrons, which a hairdryer takes care of. What you're talking about is filtering out tiny molecules, such as individual oil molecules. those are neutral. We're talking about filtering a huge virus.
(Score: 2) by EETech1 on Thursday September 03 2020, @03:36PM (1 child)
Here is a size comparison of the coronavirus to the filler media
https://www.dw.com/image/53480883_7.png [dw.com]
Average pore size is 3 micron, the coronavirus is 10-20 times smaller.
(Score: 1) by fakefuck39 on Thursday September 03 2020, @07:29PM
The mask pore size is 0.3 microns, not 3 microns. You're off by a factor of 10. Still twice as big as the virus though. Which is why we charge the mask - so the charge of the mask attracts the virus and makes it stick to the mask. In reality, most of the virus is surrounded by some other stuff like water and mucous, making the droplet much bigger. But the mask even filters the standalone viruses. Due to the charge. Which you can apply with a hairdryer at home, without damaging the mask.
Your point?