Personal Protective Equipment reuse / Covid-19

[profdc9]

In the USA (and I would imagine elsewhere) physicians use N95 respirators and other similar worldwide standards (see attached document) to prevent being infected while treating the infected.  Under ordinary circumstances, these respirators are designed to be discarded after use.  Because there is not an adequate supply to treat all of the anticipated infections, there are many ideas on how to disinfect and reuse these masks.   For example, look at

http://ppereuse.com
http://n95reuse.com

Personally, I have been working on methods of UV germicidal sterilization of these masks.  I wrote a document of how to create an ad-hoc UVGI sterilizer:

https://drive.google.com/open?id=1wF4yYgSE1n0Jqewb8JdwosTRhx0X89wF

Please spread the word about these resources to physicians that might need them.

One potential method of disinfection is ozone treatment.  Ozone (as well as nitric oxide and other nitrogen oxides) can be generated using a corona discharge.   Many of the above methods require specialized equipment or chemicals.  Perhaps a simple ozone disinfection device can be built from commonly available electronic parts that minimizes the risk of electric shock during construction and use. 

Another possibility is a device that can be used to heat enclosures to low temperatures safety, these temperatures being less than 150 C.  Look at the "dry heating" portion of this document:

https://docs.google.com/document/d/193mt42jUR8PxuONUY4A6YZsyOOmy6Psg6BDme3rjai8/edit#heading=h.h1qjojk7297y

Something like this Arduino temperature controller could be used to maintain the temperature of an enclosure at 60 C for an extended period, which is hot enough to cause accelerated degradation of the virus but not significant damage to the mask.

https://circuits4you.com/2016/06/06/arduino-temperature-controller/

Anyways, perhaps you can think of ideas on how to disinfected masks.

[rikkitikkitavi]

Dilute hydrogen peroxide , dilute hypochlorite , swimming pool chlorine (should be the instant or chock type ) consituting of bleaching powder, all readily available and not toxic like ozone in dilute aqeuos solutions. Caveat is that they are all liquid, so it might be difficult to reach all exposed sufraces in a complicated thin like a mask.

I have not read your paper, but does not UV degrade plastic in these masks? Does it reach all exposed surfaces?
Same as high temperatures., that I would imagine would degrade the plastic.
The method is effective, I have designed some water systems, all from potable water to pharmaceutical grade in where 254 nm Hg lamps did a good joob. It is just a matter of applying doeage.


To sterlize complicated structures that are diffuclt to use heat on and liquid disefectants cant be used vaporized hydrogen peroxide is commonly used, not as agressive towards materials as ozone.
And far less risky than propylen/ethenoxides.
Technically it is used mainly for room santization , using more or less portable units producing hydrogen peroxide in the 100ths ppm range in the air, circulating.
Could be used in a chamber, preferably with tight seals and just throw stuff inside so that the VHP reach all surfaces.

Or just 70+% ethanol. Lots of it. Readily available.

[johnf]

I have a paper that uses adenovirus as a proxy for corona virus to get 4 log inactivation you need 200mJ/cm of 254nm UV.
This dose is required as the corona virus is enveloped ie it is hard to get to it to damage it.
most plastics are suffering advanced damage at this level of exposure.
I've been working with low energy x-rays doses of around 1000 gray are effective in killing these viruses.
I have offered this tech to the nz Govt no response yet i have three x-ray monoblocks that could be used 2mA 160kV
this would be about 1.5 hours to get sufficient dose for 5 log or better inactivation of covid 19

[johnf]

If you want tyo make some surface disinfectant you can use benzalkonium chloride.
this is found commonly in household cleaners in differing amounts up to 200gm/litre
here in NZ 30 seconds spray and walk away is the cheapest @approx $nz30 (us$16) per 5 litres of 100gm/litre of active ingredient
for home surface use once a day of 2gm/litre wiped or sprayed on

[rikkitikkitavi]

I have a paper that uses adenovirus as a proxy for corona virus to get 4 log inactivation you need 200mJ/cm of 254nm UV.
This dose is required as the corona virus is enveloped ie it is hard to get to it to damage it.
most plastics are suffering advanced damage at this level of exposure.
I've been working with low energy x-rays doses of around 1000 gray are effective in killing these viruses.
I have offered this tech to the nz Govt no response yet i have three x-ray monoblocks that could be used 2mA 160kV
this would be about 1.5 hours to get sufficient dose for 5 log or better inactivation of covid 19

200mJ/cm2 is a LOT.  2000 Gray is ridiculous lot of radiation. It would kill a human in seconds, only the time for the heart to stop and the nerve system to shutdown. It would heat the body 0,5C.

[johnf]

Here's the paper

I didnt say 2000 gray I said 1000Gray
that is equivalent to 1000Sv about 200x lethal dose to humans. This is the typical dose given in sterilisation with Co60 systems for medical use stuff

[rikkitikkitavi]

Opps. My typo.
Yea, with X rays the Grays and Sieverts are more or less the same. At 1000 you are as dead as with 2000. Fried beans.

To recieve this dosage of a nuclear weapon you will not die of actute or immediate radiation sickness but be vaporised by the heat pulse OR smashed into very small fragments by the supersonic chock wave formed close to the hypocenter of the detonating weapon.

[klugesmith]

Gee whiz, enough grays to produce an easily measurable temperature rise !

It came up on another forum, a few years ago, in the context of neutron transmutation doping.
For 8000 volt whole-wafer thyristors, as used in HVDC power transmission, they need silicon with exceptionally uniform and well-controlled n-type doping.   Thermal neutron fluences of at least 1e16 cm^-2 transmute some of the natural 30Si to 31P in place.  Done industrially at specially equipped nuclear reactor facilities.  My comment to put the dose in perspective:



Back to this thread:  Maybe the silicon transmutation conveyors could be adapted to sterilize used PPE items, if the temperatures in hot section aren't too high.  Change the motor gearing to get much more throughput.  This could only benefit Covid care facilities very close to the reactor site.  And sterilization by neutrons would be useless if the sterile product is too radioactive