Doctors scramble for best practices on reusing medical masks during shortage

Mar 24, 2020
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There's a bit of a typo in the story. In one spot, the required temperature is given as 58 degrees F, not 158.
 
Mar 25, 2020
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I have sleep apnea. I currently use a SoClean machine that uses ozone to clean my mask. Based on what I have read, Ozone has been proven to kill the SARs Coronavirus. I have bought a second machine and modified it slightly so it is a completely closed unit that bathes the contents in Ozone for 7 minutes. The unit makes you wait about two hours for the ozone to be changed back to oxygen before opening the cleaner. I run the mask through two cleaning cycles.

Based on what I have read, a study is going to be published that shows Ozone kills the COVID-19 virus. Why don't the hospitals build ozone chambers to decontaminated the masks after use. Ozone generators are very cheap.
 
Mar 26, 2020
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We recently purchased reusable N95 - N99 masks. These masks have a mesh shell that can be washed in soapy water, and a replaceable filter insert with an active carbon component. We also happen to have devices that use UV light to clean cell phones (Phone Soap). I will be using this device to sanitize our mask's filter inserts, hoping to extend their longevity (replacements are out of stock and should go to health workers when available again). Hopefully those with the means can report on the effectiveness of these devices, or the effectiveness of exposing used masks to strong sunlight.
 
Mar 28, 2020
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Fact Checking:

Rafi says that Annals of Occupational Hygiene states that:
"70 C / 158 F heating in a kitchen-type of oven for 30 min, or hot water vapor from boiling water for 10 min, are additional effective decontamination methods."

I read the article in Annals of Occupational Hygiene and can not find the quote.

Could someone give me a link to that quote. I do not want to distribute this quote if it is not true


Thanks

Gary
 
Mar 28, 2020
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I have sleep apnea. I currently use a SoClean machine that uses ozone to clean my mask. Based on what I have read, Ozone has been proven to kill the SARs Coronavirus. I have bought a second machine and modified it slightly so it is a completely closed unit that bathes the contents in Ozone for 7 minutes. The unit makes you wait about two hours for the ozone to be changed back to oxygen before opening the cleaner. I run the mask through two cleaning cycles.

Based on what I have read, a study is going to be published that shows Ozone kills the COVID-19 virus. Why don't the hospitals build ozone chambers to decontaminated the masks after use. Ozone generators are very cheap.
Ozone is going to degrade the material. I would keep a close eye on whether there seems to be any change in the pressure needed to respire.
 
Mar 28, 2020
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Very little is known about how to properly reuse medical masks to fight infectious diseases, but some best practices are starting to emerge.

Doctors scramble for best practices on reusing medical masks during shortage : Read more
Since the SARS and MERS epidemics, there is a fair amount of scientific literature looking at the need to sterilize standard N95 respirators in the event of a pandemic. Two US government studies from that time period posited that the US alone would need 90 or 360 million masks in the event of an influenza pandemic. Well, here we are.

The most realistic method I've seen that can be done on a small scale - or scaled up for larger use without a lot of resources- is steam sterilization in Microwaveable Steam Bags. See:

Basically, masks and respirators are sterilized by microwaving in the microwaveable bags that are readily available for sterilizing baby bottles and breast pumps. These are preferred to the bags made for food because they are multi-use, whereas the food bags are single use.

This method could be easily scaled up. Imagine a process where mask users place used masks in these bags. The bags are taken to a room set up with negative air pressure (for infectious agent containment), water available to fill the bags, and standard consumer grade microwave ovens. The ovens are arranged so that they are run from a single switch outside the room (to reduce potential worker exposure to microwave scatter). The bags have the requisite amount of water added, are loaded into the ovens, the worker exits the room and triggers the ovens. The worker then re-enters, removes the bags from the ovens, takes them to another room set up with screens on racks and forced warm air for drying. The masks are taken from the bags and placed on the screens for drying. They are then placed back out for users. Since the entire sterilization process (including drying) could be set up for 6-15 cycles/hour and racks of ovens take relatively little room, it should be possible to set up for processing 100s to 1000s of masks per hour, all with off the shelf equipment.
 
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Mar 26, 2020
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Here’s a link to an article discussing the use of vaporized hydrogen peroxide to disinfect N95 masks:

https://techcrunch.com/2020/03/27/duke-university-uses-vaporized-hydrogen-peroxide-to-clean-n95-face-masks-for-reuse/

It is reported as an effective disinfectant method. Perhaps hospitals without the units specifically designed for this disinfecting method could jury-rig one as follows:
  • Place a benchtop isolation chamber in a hood.
  • Place a cool mist ultrasonic humidifier filled with hydrogen peroxide in the isolation chamber.
  • Place the masks to be disinfected in the isolation chamber, hung in some fashion to expose the entire surface.
  • Seal the isolation chamber and turn on the humidifier.
  • When the disinfecting cycle is completed (TBD empirically), vent the isolation chamber in the hood.
Testing would be required to determine if this method could achieve the vapor concentrations needed to be effective.

Please don’t try this at home! Breathing hydrogen peroxide vapor is dangerous!
 
Mar 25, 2020
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Ozone is going to degrade the material. I would keep a close eye on whether there seems to be any change in the pressure needed to respire.
Steve,

The Ozone exposure is very short. My CPAP machine has probably through 700 cleaning cycles. What type of deterioration do you expect to see in the materials.

Thanks for you help,
Rich
 
Mar 28, 2020
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I expect the filter media (generally a non-woven fabric) to be degraded. Basically, you're trying to oxidize the pathogen, but other materials exposed to the ozone will be affected. We've got an ozone generator we use to remove smoke and mold odors from books, but also inside musty motor vehicles. One hour in a closed vehicle is enough to make rubber bands brittle and easily breakable. So, the effect on the filter material may be similar, reducing its filtration effectiveness. You could try it and see if there is ay detectable change in the pressure required for inhalation and exhalation. If the needed pressure changes that could indicate the material is "clogging" (possibly from small pieces that have disintegrated) or (the reverse) been removed so filtration is reduced. The wiggle here is that the test sensitivity (your subjective breathing experience) may not be sensitive enough to detect changes in airflow. Multiple ozone exposures over time may be eve more difficult to detect because your comparing with the very last time you used the filter, not its initial condition. I hope that makes sense.
But if its a choice between the ozone and nothing . . .
Still, if you've got a microwave oven the wet steam in a bag method has some testing behind it.
 
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Mar 28, 2020
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I'd be wary of whether the UV is actually reaching the interior of the material sufficiently. Sufficient energy and exposure for the length of time needed to decontaminate the interior of the filter fabric where viruses may be trapped may also be sufficient to degrade the material.
 
Apr 1, 2020
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Fact Checking:

Rafi says that Annals of Occupational Hygiene states that:
"70 C / 158 F heating in a kitchen-type of oven for 30 min, or hot water vapor from boiling water for 10 min, are additional effective decontamination methods."

I read the article in Annals of Occupational Hygiene and can not find the quote.

Could someone give me a link to that quote. I do not want to distribute this quote if it is not true


Thanks

Gary
I agree with Gary. I don't see reference to the quote in the article. Livescience, what say you? Is this fake news?
 
Apr 5, 2020
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Fact Checking:

Rafi says that Annals of Occupational Hygiene states that:
"70 C / 158 F heating in a kitchen-type of oven for 30 min, or hot water vapor from boiling water for 10 min, are additional effective decontamination methods."

I read the article in Annals of Occupational Hygiene and can not find the quote.

Could someone give me a link to that quote. I do not want to distribute this quote if it is not true


Thanks

Gary

The quote in the article inaccurate and misconstrued. The original information was incorrectly quoted from a document produced by Stanford (https://stanfordmedicine.app.box.com/v/covid19-PPE-1-2). The report tested the use of "blanket warming oven at hospitals," which is why the temperature (70C) is so low. Most home ovens do not operate at such low temperatures.
 
Apr 11, 2020
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Fact Checking:

Rafi says that Annals of Occupational Hygiene states that:
"70 C / 158 F heating in a kitchen-type of oven for 30 min, or hot water vapor from boiling water for 10 min, are additional effective decontamination methods."

I read the article in Annals of Occupational Hygiene and can not find the quote.

Could someone give me a link to that quote. I do not want to distribute this quote if it is not true


Thanks

Gary
Closest reference I could find to this important question - Conducted on SARS in 2003. Showed that oven at 75 degrees for 30 minutes made SARS non-infectious. Didn't find similar study on Covid 19.

Biomed Environ Sci. 2003 Sep;16(3):246-55.
Stability of SARS coronavirus in human specimens and environment and its sensitivity to heating and UV irradiation.
Viruses stayed stable at 4 degrees C, at room temperature (20 degrees C) and at 37 degrees C for at least 2 h without remarkable change in the infectious ability in cells, but were converted to be non-infectious after 90-, 60- and 30-min exposure at 56 degrees C, at 67 degrees C and at 75 degrees C, respectively


Furthermore, N-95 masks were shown to stand the repeated stress of baking.

From Stanford, also referenced in the quote from Live Science the quote (where Gary's misquote appeared).

Can N95 facial masks be used after disinfection? And for how many times?

"With respect to the hot air (75 °C, 30 min, 20 cycles), we found that an N95 mask did not suffer any mechanical deformation and the ear straps retained proper elasticity required for use."


75 degrees Centigrade, is 167 degrees Fahrenheit - my oven will go as low as 175, close enough. I'm going to bake my only mask at 175 degrees for 30 minutes every now and then.

Todd Swanson, MD, MPH
 
Apr 11, 2020
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Closest reference I could find to this important question - Conducted on SARS in 2003. Showed that oven at 75 degrees for 30 minutes made SARS non-infectious. Didn't find similar study on Covid 19.

Biomed Environ Sci. 2003 Sep;16(3):246-55.
Stability of SARS coronavirus in human specimens and environment and its sensitivity to heating and UV irradiation.
Viruses stayed stable at 4 degrees C, at room temperature (20 degrees C) and at 37 degrees C for at least 2 h without remarkable change in the infectious ability in cells, but were converted to be non-infectious after 90-, 60- and 30-min exposure at 56 degrees C, at 67 degrees C and at 75 degrees C, respectively


Furthermore, N-95 masks were shown to stand the repeated stress of baking.

From Stanford, also referenced in the quote from Live Science the quote (where Gary's misquote appeared).

Can N95 facial masks be used after disinfection? And for how many times?

"With respect to the hot air (75 °C, 30 min, 20 cycles), we found that an N95 mask did not suffer any mechanical deformation and the ear straps retained proper elasticity required for use."" 1) Hot air applied over 20 cycles did not degrade the filtration efficiency (>95%)."


75 degrees Centigrade, is 167 degrees Fahrenheit - my oven will go as low as 175, close enough. I'm going to bake my only mask at 175 degrees for 30 minutes every now and then.

Todd Swanson, MD, MPH
 
Apr 14, 2020
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Here is the actual citation related to using an oven at 75 degrees C:
Biomed Environ Sci. 2003 Sep;16(3):246-55.
Stability of SARS coronavirus in human specimens and environment and its sensitivity to heating and UV irradiation.

The studies (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2781738/ and https://stanfordmedicine.app.box.com/v/covid19-PPE-1-2) referred to in the above article were only looking at the stability of the masks holding up after disinfection, with the masks holding up best after using the oven method.

Hope this clarifies
 
Apr 19, 2020
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Was hoping my ozone generator could be used to sterilize my NP95 which relies on polypropylene material, until I read this:
 

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