7 ms·

Performance, Protection, and Sterilization of Face Mask Materials

80 points by imagetic 7y ago

a-wu 7y ago
There's been a lot of press about people making their own face masks out of fabric and it got me thinking about copper-impregnated fabric (if you watch enough late-night TV you'll have seen those CopperFit infomercials). Copper itself has antimicrobial properties (studies say SARS-CoV-2 only lives 4 hours on copper), but does anyone know if there is enough copper content in those fabrics to make them a better fabric for face masks than cotton?
- foxyv 7y ago
  I think it's better to just wash them in soap and water when you get home. A good soap will kill the heck out of viruses.
  - prostheticvamp 7y ago
    Or spray with bleach
    - concerned_user 7y ago
      What if you dip in isopropyl alcohol then dry, sounds safer than bleach and less destructive for the fabric. Bleach is chlorine you would have to wash it afterwards.
      - CarVac 7y ago
        Alcohol will destroy the charges that make the fabric effective for small particle sizes, according to the article.
        clort 7y ago
        that is the N95 masks made of blown polypropylene, not cloth masks made at home (for example two layers of teatowel is quite an effective filter apparently)
  - jsight 7y ago
    I think he is asking if it might improve the performance overall, not necessarily about sterilization. There has been some talk of using salt, for example: https://www.businessinsider.com/mask-coated-in-salt-neutralizes-viruses-like-coronavirus-2020-2 https://www.businessinsider.com/mask-coated-in-salt-neutrali...
    - p2detar 7y ago
      Thanks, that was pretty informative. We have a bunch of one time use standard surgical masks at home. I wonder if I can just put them in a bag of salt after single use.
- mantap 7y ago
  I personally wouldn't. Fabric sheds, having tiny microparticles of copper lodged in your lungs is probably not advisable.
- gruez 7y ago
  >Copper itself has antimicrobial properties (studies say SARS-CoV-2 only lives 4 hours on copper), but does anyone know if there is enough copper content in those fabrics to make them a better fabric for face masks than cotton? I think you answered your own question. Viruses only get killed if they're on copper for 4 hours, so it might be useful if you wanted a self-disinfecting mask, but if the material itself doesn't filter properly the antimicrobial properties of copper doesn't matter because the viruses fly straight through and aren't affected by the copper.
  - a-wu 7y ago
    Right. I should've phrased the question as: is the copper content sufficiently high enough to make a significant impact on the disinfection rate compared to just say, cotton? Obviously it won't make a difference (I think?) during wear, but if it the virus dies quicker than on cotton then one could potentially disinfect the mask less frequently.
Abishek_Muthian 7y ago
This is very useful, I have made a 3 layer Qualitative Filter based face mask with middle layer soaked in brine solution for possible virus deactivation[1]. With more governments officially recommending DIY face masks for public, so that proper N95 masks can be left to the health care workers; I would love to get my mask scientifically tested. [1]https://abishekmuthian.com/diy-qualitative-filter-face-mask/ https://abishekmuthian.com/diy-qualitative-filter-face-mask/
- Androider 7y ago
  The CDC suggests it might be possible to re-use masks after storing them in a paper bag for a while https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguid... I also wonder how such re-use of a mask combined with more durable N99 masks that are ordinarily rated at hundreds of hours for the filter (compared to 8 hours for your average N95 mask) could be used as a more permanent mask for households if only used occasionally when going to get groceries for example.
omgJustTest 7y ago
"He does not give any advice on the performance of the re-sterilized N95 or mask against the virus." So... we want the attention but not the risk of you taking our advice. If you have something of interest, why haven't you contacted people whose lives you could save?
- dang 7y ago
  Single-purpose accounts aren't allowed on HN.
- imagetic 7y ago
  meaning it's not tested against the actual virus. He is a materials scientist, the one who invented the process we use for n95 rated materials.
nominated1 7y ago
What if I have X masks and rotate their usage without any cleaning at all. Would this allow the virus to die naturally without the need to clean the mask?
- renewiltord 7y ago
  Yes, this will work and is current healthcare professional practice in many places. It will take a few days, though, so people usually line up like 5-6 and then rotate through those. If you can heat the masks that's cool, too, but then you have to make sure you don't damage the elastic or seal. Waiting will work.
- cryoshon 7y ago
  according to the OP paper, that's an unproven strategy. i can't find anything else supporting it in the literature linked by that paper either. so the real answer is that we don't know. however, while it appears to be unproven, given what we know about how long the virus survives on different materials, i would say that it is probable that leaving a mask aside in a dry spot for a week or so is effective at ensuring there are no viable viral particles remaining on the mask. as long as we're using unproven decontamination methods, i'd say to also leave the external surface of the mask in direct sunshine for a few hours too. as the OP paper notes, sun bleaching / UVR does degrade the quality of the filtration by a small amount (around 1.5% if i recall) but it's also effective at destroying viral particles in a short period.
oski 7y ago
If you know any healthcare workers (doctors or nurses), have them checkout https://www.n95decon.org/ https://www.n95decon.org/ to follow the latest on sterilizing face masks. N95 masks should be reserved for HCWs as there is a major shortage. Most people should just wear nonmedical fabric or homemade masks, but everyone should wear some kind of mask when out and near other people. See https://shouldiwearafacemask.com https://shouldiwearafacemask.com
K2h 7y ago
Great resource, the last one I was working off of on this topic was from Stanford: https://aim.stanford.edu/covid-19-evidence-service/ https://aim.stanford.edu/covid-19-evidence-service/ -Latest as of 3/29 V1.2 https://stanfordmedicine.box.com/v/covid19-PPE-1-1 https://stanfordmedicine.box.com/v/covid19-PPE-1-1
motohagiography 7y ago
Couple questions for scientists on the thread: - If it is true that soap kills the virus by breaking up it's outer lipid layer, does that mean soaps and degreasing agents and coatings may also kill it on surfaces like clear visors, gloves and other fabrics? - While N95 (non oil particulate) masks are considered sufficient, and P and R 95+ (oil particulate filters) are not considered necessary - are those oil particulate filters also considered sufficient? - can folded, oil-absorbant paper shop cloths provide more protection than cut-up t-shirts and regular cotton?
- TylerE 7y ago
  Yes... P/R95 is a strict sub-set of N95. It's an additional capability.
lootsauce 7y ago
Tech Ingredients did a fantastic video on the subject recently, I love everything from this guy and the recent series in response to COVID-19 is great stuff. https://www.youtube.com/watch?v=2UdtKssU7po https://www.youtube.com/watch?v=2UdtKssU7po
- lootsauce 7y ago
  After reading the article there is an important insight I did not know of and clearly neither did Tech Ingredients as they demonstrate use of alcohol. from the article "the FE (filtration efficiency) of these masks is influenced by the electrostatic charges embedded within the fibers of the filtration layer(s) in the interior part of the masks." "... using alcohol will erase the charges. However, exposing the masks to air at elevated temperatures such as 70℃ for 30 minutes allows the charges to be retained."
prpl 7y ago
Naively I would guess an easy way to sterilize is in a ziplock bag under water (sous vide) at 70C
- imagetic 7y ago
  That's a good question! https://community.anovaculinary.com/t/sous-vide-a-face-mask-for-sterilization/25497 https://community.anovaculinary.com/t/sous-vide-a-face-mask-...

80 points by imagetic 7y ago

a-wu 7y ago

There's been a lot of press about people making their own face masks out of fabric and it got me thinking about copper-impregnated fabric (if you watch enough late-night TV you'll have seen those CopperFit infomercials). Copper itself has antimicrobial properties (studies say SARS-CoV-2 only lives 4 hours on copper), but does anyone know if there is enough copper content in those fabrics to make them a better fabric for face masks than cotton?

foxyv 7y ago
I think it's better to just wash them in soap and water when you get home. A good soap will kill the heck out of viruses.
- prostheticvamp 7y ago
  Or spray with bleach
  - concerned_user 7y ago
    What if you dip in isopropyl alcohol then dry, sounds safer than bleach and less destructive for the fabric. Bleach is chlorine you would have to wash it afterwards.
    - CarVac 7y ago
      Alcohol will destroy the charges that make the fabric effective for small particle sizes, according to the article.
      - clort 7y ago
        that is the N95 masks made of blown polypropylene, not cloth masks made at home (for example two layers of teatowel is quite an effective filter apparently)
- jsight 7y ago
  I think he is asking if it might improve the performance overall, not necessarily about sterilization. There has been some talk of using salt, for example: https://www.businessinsider.com/mask-coated-in-salt-neutralizes-viruses-like-coronavirus-2020-2 https://www.businessinsider.com/mask-coated-in-salt-neutrali...
  - p2detar 7y ago
    Thanks, that was pretty informative. We have a bunch of one time use standard surgical masks at home. I wonder if I can just put them in a bag of salt after single use.
mantap 7y ago
I personally wouldn't. Fabric sheds, having tiny microparticles of copper lodged in your lungs is probably not advisable.
gruez 7y ago
>Copper itself has antimicrobial properties (studies say SARS-CoV-2 only lives 4 hours on copper), but does anyone know if there is enough copper content in those fabrics to make them a better fabric for face masks than cotton? I think you answered your own question. Viruses only get killed if they're on copper for 4 hours, so it might be useful if you wanted a self-disinfecting mask, but if the material itself doesn't filter properly the antimicrobial properties of copper doesn't matter because the viruses fly straight through and aren't affected by the copper.
- a-wu 7y ago
  Right. I should've phrased the question as: is the copper content sufficiently high enough to make a significant impact on the disinfection rate compared to just say, cotton? Obviously it won't make a difference (I think?) during wear, but if it the virus dies quicker than on cotton then one could potentially disinfect the mask less frequently.

Abishek_Muthian 7y ago

This is very useful, I have made a 3 layer Qualitative Filter based face mask with middle layer soaked in brine solution for possible virus deactivation[1]. With more governments officially recommending DIY face masks for public, so that proper N95 masks can be left to the health care workers; I would love to get my mask scientifically tested. [1]https://abishekmuthian.com/diy-qualitative-filter-face-mask/ https://abishekmuthian.com/diy-qualitative-filter-face-mask/

Androider 7y ago
The CDC suggests it might be possible to re-use masks after storing them in a paper bag for a while https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguid... I also wonder how such re-use of a mask combined with more durable N99 masks that are ordinarily rated at hundreds of hours for the filter (compared to 8 hours for your average N95 mask) could be used as a more permanent mask for households if only used occasionally when going to get groceries for example.

omgJustTest 7y ago

"He does not give any advice on the performance of the re-sterilized N95 or mask against the virus." So... we want the attention but not the risk of you taking our advice. If you have something of interest, why haven't you contacted people whose lives you could save?

dang 7y ago
Single-purpose accounts aren't allowed on HN.
imagetic 7y ago
meaning it's not tested against the actual virus. He is a materials scientist, the one who invented the process we use for n95 rated materials.

nominated1 7y ago

What if I have X masks and rotate their usage without any cleaning at all. Would this allow the virus to die naturally without the need to clean the mask?

renewiltord 7y ago
Yes, this will work and is current healthcare professional practice in many places. It will take a few days, though, so people usually line up like 5-6 and then rotate through those. If you can heat the masks that's cool, too, but then you have to make sure you don't damage the elastic or seal. Waiting will work.
cryoshon 7y ago
according to the OP paper, that's an unproven strategy. i can't find anything else supporting it in the literature linked by that paper either. so the real answer is that we don't know. however, while it appears to be unproven, given what we know about how long the virus survives on different materials, i would say that it is probable that leaving a mask aside in a dry spot for a week or so is effective at ensuring there are no viable viral particles remaining on the mask. as long as we're using unproven decontamination methods, i'd say to also leave the external surface of the mask in direct sunshine for a few hours too. as the OP paper notes, sun bleaching / UVR does degrade the quality of the filtration by a small amount (around 1.5% if i recall) but it's also effective at destroying viral particles in a short period.

oski 7y ago

If you know any healthcare workers (doctors or nurses), have them checkout https://www.n95decon.org/ https://www.n95decon.org/ to follow the latest on sterilizing face masks. N95 masks should be reserved for HCWs as there is a major shortage. Most people should just wear nonmedical fabric or homemade masks, but everyone should wear some kind of mask when out and near other people. See https://shouldiwearafacemask.com https://shouldiwearafacemask.com

K2h 7y ago

Great resource, the last one I was working off of on this topic was from Stanford: https://aim.stanford.edu/covid-19-evidence-service/ https://aim.stanford.edu/covid-19-evidence-service/ -Latest as of 3/29 V1.2 https://stanfordmedicine.box.com/v/covid19-PPE-1-1 https://stanfordmedicine.box.com/v/covid19-PPE-1-1

motohagiography 7y ago

Couple questions for scientists on the thread: - If it is true that soap kills the virus by breaking up it's outer lipid layer, does that mean soaps and degreasing agents and coatings may also kill it on surfaces like clear visors, gloves and other fabrics? - While N95 (non oil particulate) masks are considered sufficient, and P and R 95+ (oil particulate filters) are not considered necessary - are those oil particulate filters also considered sufficient? - can folded, oil-absorbant paper shop cloths provide more protection than cut-up t-shirts and regular cotton?

TylerE 7y ago
Yes... P/R95 is a strict sub-set of N95. It's an additional capability.

lootsauce 7y ago

Tech Ingredients did a fantastic video on the subject recently, I love everything from this guy and the recent series in response to COVID-19 is great stuff. https://www.youtube.com/watch?v=2UdtKssU7po https://www.youtube.com/watch?v=2UdtKssU7po

lootsauce 7y ago
After reading the article there is an important insight I did not know of and clearly neither did Tech Ingredients as they demonstrate use of alcohol. from the article "the FE (filtration efficiency) of these masks is influenced by the electrostatic charges embedded within the fibers of the filtration layer(s) in the interior part of the masks." "... using alcohol will erase the charges. However, exposing the masks to air at elevated temperatures such as 70℃ for 30 minutes allows the charges to be retained."

prpl 7y ago

Naively I would guess an easy way to sterilize is in a ziplock bag under water (sous vide) at 70C

imagetic 7y ago
That's a good question! https://community.anovaculinary.com/t/sous-vide-a-face-mask-for-sterilization/25497 https://community.anovaculinary.com/t/sous-vide-a-face-mask-...