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Coronavirus 2019-nCoV. FAQ on Respiratory Protection and Disinfection

Chinese coronavirus, aka Wuhan pneumonia, has become one of the hottest topics this week. In the classic “who is to blame and what to do”, traditionally, I am concerned only with the second part. Today, under the cut - an article about disinfection, masks and decontamination of rooms. Combined in one article several notes from his telegram channel . We bookmark and send a helmet to friends!



UFO Care Minute


The pandemic COVID-19, a potentially severe acute respiratory infection caused by the SARS-CoV-2 coronavirus (2019-nCoV), has officially been announced in the world. There is a lot of information on Habré on this topic - always remember that it can be both reliable / useful, and vice versa.

We urge you to be critical of any published information.


Official sources

, .

Wash your hands, take care of your loved ones, stay at home whenever possible and work remotely.

Read publications about: coronavirus | remote work

I must say right away that due to the relative novelty of 2019-nCoV, it’s too early to wait for any studies, all that remains is to appeal to the old developments obtained during the struggle, first with SARS, and then with MERS, because one family, anyway ...

I. Hands + surfaces


In general, regarding the disinfection of hands / surfaces with chemical disinfectants, I found an interesting article where the authors compared the virucidal activity of the following common chemicals:

- Sodium hypochlorite 0.01% - 0.05% - 0.1%;
- Ethanol 70%;
- Benzalkonium chloride 1%;
- Chlorhexidine bigluconate 1%;
- 2-benzyl-chlorophenol 2%;
- Peracetic acid 0.035%.

A WHO study of SARS-coronavirus shows that the virus survives up to 48 hours on plastic surfaces and up to 4 days in liquid media. But in the case of using any of the disinfectants, the activity of the virus decreases very, very quickly. The mentioned article shows that SARS coronavirus is completely inactivated by disinfectants such as peracetic acid, ethanol 70%, sodium hypochlorite 0.05% and 0.1%, chlorhexidine bigluconate 1% and 2-benzyl-chlorophenol 2% after treatment in within 1 minute. It takes longer for benzalkonium. The truth is that with regard to biological waste (sputum, human excretion, etc.), only 0.1% sodium hypochlorite and 2% 2-benzyl-chlorophenol with a contact time of more than 2 minutes showed the ability to destroy viral RNA.

In a later studyfour different hand disinfectants were used to test virucidal activity - 1) based on 45% isopropanol, 30% n-propanol and 0.2% mesetronium ethyl sulfate; 2) based on 80% ethanol; 3) a gel based on 85% ethanol; 4) antiviral gel based on 95% ethanol - hand treatment time = 30 seconds. As disinfectants for surfaces used means - 1) based on benzalkonium chloride and laurylamine; 2) based on benzalkonium chloride, glutaraldehyde and didecyldimonium chloride; 3) based on magnesium monoperphthalate. Processing time - from 15 to 60 minutes. As a result, it was found that SARS-CoV was inactivated to a level below the detection limit in the case of treatment with any of these drugs. This means that as a disinfectant (both hands and surfaces), you can use any meanscontaining the above components.

One of the notes from my channel in which I taught readers how to wash their hands and prepare alcohol gel:

about protecting your hands from bacteria and viruses
.

. . ( «hand sanitizer»). ( , , ..). ( , , , ). ( - ).

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. — . , , >60% ( « » — CDC, , 60% 40% ). , 70-90%. , . . 70:30 , , . , , , , . « », .. .

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, , . , . , ( « »). ( , ) . , , . , « » , (. , /carbomer). — .

+ , .. ( - ). - ( , 10 ~ 8$) ( , ~60%). — , :)


Your humble servant also prepared a personal disinfectant for himself (on KDPV). I’m a persistent fan of PHMG , mainly because of their ability to form films with protective activity when dried, and there was no powder benzalkonium at hand ( well, who I’m fooling, knowing personally who discovered this substance, I trust these people more than yourself ). In the photo - tubes for yourself and the “that guy” in the long-wave UV. Fluorescence due to fluorescein, which I added to the composition, in the hope that in UV it will be possible to control the degree of coverage of the hands with a protective composition. By components - 70% ethanol + PHMG and thickened to viscosity “by eye” using carbomer.


An important nuance when using disinfecting gels is the exposure time. It should be at least 30 seconds (in the mentioned articles about such an exposure). In this regard, slightly drying gel is much more effective than wipes with antibacterial impregnation.

Note about the alcohol used. Traditionally, alcoholic hand sanitizers use mixtures of isopropyl alcohol, ethanol (ethanol) or n-propanol in various concentrations. The most effective options are from 60 to 95% alcohol. It should be borne in mind that viruses are best affected by alcohols over 90%. Isopropyl alcohol kills99.99% or more of all non-spore forming bacteria in less than 30 seconds. Alcohol disinfectants containing at least 70% alcohol (most often ethanol) kill 99.9% of the bacteria on the hands 30 seconds after application and from 99.99% to 99.999% in one minute. As for the effectiveness of the application for the destruction of coronavirus (SARS as the oldest), here is such a picture:


Minimum titer reduction factor (log10) = decimal logarithm of the relationship between the total number of viruses before processing and the total number after processing, i.e. actually an indicator of the effectiveness of disinfection.

In general, if you consider the options available, isopropyl alcohol is considered more effective against bacteria, and ethanol is more effective against viruses, but this depends on the concentration of the disinfecting agent and the microorganism being treated (for example, isopropyl alcohol is more lipophile than ethyl alcohol, therefore less active against hydrophilic viruses ( polio virus , etc.)

Important: The alcohol disinfectant should be thoroughly rubbedin the arms and lower part of the forearm for at least 30 seconds and then allow to air dry. It is worth noting that there are certain situations in which hand washing with water and soap is preferable to an alcohol-based disinfectant. This is a) the removal of bacterial spores of Clostridioides difficile , b) the removal of parasites from the skin such as cryptosporidia , c) the removal of certain viruses, for example the Norwalk virus (95% ethanol and exposure over 30 minutes are required to destroy it). In addition, hands should still be washed before handling if they are contaminated with something (oils, etc.).

II. Air ~ Aerosols


A much more controversial issue is air disinfection. Once again, I was convinced of this by writing an article about masks for coronavirus and advising everyone to use ultraviolet light to clean the air in the room from viral particles. There were several people who questioned (!) The fact that 254 nm ultraviolet light could destroy the virus.

In general, in the studythe authors tested the activity of hard ultraviolet radiation (in plain language - “quartz lamp”) for viral aerosols, i.e. on the very particles with which the virus is carried in the environment and enters our lungs (and which I suggested to capture using HEPA / ULPA filters). What did you manage to install? But it was possible to establish that viruses of different classes react differently to ultraviolet light. For example, aerosols with adenoviruses (causing acute respiratory infections) were quite resistant to ultraviolet radiation.


In their case, a decrease in the number of viable viral aerosols by less than 1 logarithm was observed only at a dose of ultraviolet radiation of 2608 μW / cm2. But on the other hand, the susceptibility of aerosols of the coronavirus was 7-10 times higher than that of the adenovirus. Interestingly, in the case of processing the room with ultraviolet light, in contrast to bacterial aerosols, the protective effect of high relative humidity was not observed. Those. even in the steam room you can kill the coronavirus with an ultraviolet lamp.

Even cooler articlewas published in the journal Aerosols. In it, the authors evaluated the effectiveness of hard bactericidal ultraviolet on viral aerosols, and examined viruses with different types of nucleic acids (single-stranded RNA, single-stranded DNA, double-stranded RNA; double-stranded DNA) at different relative humidity during exposure to ultraviolet radiation. For airborne viruses, the ultraviolet dose for 90% inactivation was: 339–423 μW s / cm2 for single-stranded RNA, 444–494 μW s / cm2 for single-stranded DNA, 662–863 μW s / cm2 for double-stranded RNA and 910–1196 μW s / cm2. for double stranded DNA. It is noteworthy that for all four tested classes of viruses for 99% inactivation, a 2 times higher dose of ultraviolet radiation was required than was necessary to achieve 90% inactivation. Also foundthat airborne viruses with single-stranded nucleic acid (RNA and DNA) were more susceptible to ultraviolet inactivation than with double-stranded RNA and DNA. For all viruses tested with the same degree of inactivation, the dose of ultraviolet radiation at a relative humidity of 85% was higher than at a relative humidity of 55%. Perhaps this is due to the fact that the sorption of water on the surface of the virus provides protection against DNA or RNA damage caused by ultraviolet radiation. Thus, this article is an exhaustive guide to selecting the power of home ultraviolet. By the way, dose = exposure time * radiation intensity. Well, the method works - no doubt. Under the spoiler, there’s a note on the susceptibility figures for some common viruses (look for our Wuhan friends there)Under the spoiler, there’s a note on the susceptibility figures for some common viruses (look for our Wuhan friends there)

Average UV rate constants for animal viruses and phages


By the way, “Wuhan pneumonia” contains single-stranded RNA, so to work with it, you need 339–423 µW s / cm2 of ultraviolet radiation with a wavelength of 254 nm (90% air disinfection).


In order not to once again send readers to my old " UV article ", I’ll hide the most important information about the lamps under the spoiler.

excerpts from the article

...


, («») , , . , , . .. ( . ultra — , , . viola — ). , , Fe2O3, Cr2O3 TiO2. «» TiO2, 180 ( UVC ).

. (« ») 368—371 , , - , / ( NiO/CoO 9%). (SrB4O7:Eu2+), 350—353 — (BaSi2O5:Pb2+).

.


( 21 ). , . >380 , 400 . .. aliexpress , , - , . «» (… , , , .., ) — . , 5-7 , , ( , «254 »). « » ( , ), 245 , - 300 (~ 100 ).


300 , 140$. , smd.


ThorLabs. UVC (280 ), , - , , 205 — 315 . . , « ».


- 365


, , - . - - (, , -) «» . E27. G23 ( Osram Puritec HNS S 7W) « ».

. , , L L — UV-9W UV-9W-L. , ( «» ) — . , . . . L ( ), L — . ( 9~12 ) 90% , …


. , G5/2G11/G13 .





As for ozone, this friend crumbles everything. Indiscriminately (including rubber products in the room). Therefore, when using Chinese ozonizers, about which I wrote a little in the last article, it is important to control the processing time. For example, the article tested the effectiveness of ozone on bacteriophages (which, incidentally, die for a long time under the influence of classical ultraviolet radiation). It was found that the number of surviving viruses in airborne aerosols was expected to decrease exponentially with increasing doses of ozone. Airborne viruses required doses of ozone from 0.34-1.98 / 0.80-4.19 min-mg / m3 for inactivation of 90% and 99%, respectively. As in the case of ultraviolet, the dose of ozone for inactivation of 99% was 2 times higher than for inactivation of 90%. Viruses with a more complex architecture have been found to be less susceptible to ozone inactivation,than viruses with simple architecture. In addition, with the same degree of air deactivation, the required ozone concentration at a relative humidity of 85% was lower than at a relative humidity of 55%. Perhaps this is due to the formation of more free radicals that reacted with water vapor. Nevertheless, the verdict of the article is unequivocal - ozone is very effective for the decontamination of any viruses carried with aerosols (airborne droplets). So, guys, a compact ozonizer, first surfaced inThe article’s verdict is unequivocal - ozone is very effective in deactivating any viruses carried with aerosols (airborne droplets). So, guys, a compact ozonizer, first surfaced inThe article’s verdict is unequivocal - ozone is very effective in deactivating any viruses carried with aerosols (airborne droplets). So, guys, a compact ozonizer, first surfaced inarticle about ozone thanksMeklon, you still need to have a home in case of a viral epidemic.

Generalized picture disinfectant / effect on the virus


Disclaimer: And let me remind you again . OZONE - THE STRONGEST OXIDIZER! OZONE - POISON! Work with it requires special care, and it breaks up NOT INSTANTLY! Check seven times the protective equipment, ventilation, timers on the ozonizer before starting the disinfection process. Remember that you do independent ozonation at your own peril and risk!


III. About the right masks


I heard somewhere about the fact that disposable face masks suddenly became the best-selling product in China in connection with the epidemic. He was indignant, for he immediately recalled a long-standing study, the results of which were published in the journal Lancet . The bottom line - statistically significant protection against the SARS virus was somehow provided only by surgical four-layer masks and masks of the “N95” type. Disposable paper and ordinary three-layer - are as effective as a scarf or scarf tied around the face. True , the effectiveness of the vaunted N95 was later refuted .


All that masks can help to do is reduce the risk of getting the virus through a “splash” from sneezing or coughing and provide some protection from the transmission of the infection from hand to mouth. Although most people even wear a mask, they nevertheless stick a hand under it to rub their face / scratch their nose, etc. Plus, almost everyone forgets that the mask / bandage should be changed as often as possible, a maximum of three hours, otherwise it itself becomes a source of infection. WHO also interprets about the same in its recommendations . So it makes sense to carry a cheap mask with you only in one case - to give it to a sneezing / coughing citizen, along with the recommendation "do not distribute coronavirus."

The question arises: is there any sense in wearing a mask to protect yourself from viruses in the air and which one? I answer! There is a reason to wear it, but only full-face, covering the eyes (because coronaviruses can enter the body not only through the mucous membrane of the lungs, but also through the eyes). The poor efficiency of the rag mask is precisely due to the nanoscale particles of the virus, poor fit and inadequate eye protection.

Note about the particle size of the virus. The diameter of coronavirus virions, for example SARS, is from 100 to 140 nanometers (this is 0.1..0.14 microns). Most coronaviruses have spikes that add another 20 nm to the diameter. Those. viruses are included in the so-called subset of PM2.5, which describes all particles in the range from 10 nm to 2.5 microns. Accordingly, filters for PM2.5 should also work with viral aerosols. In addition, it is traditionally believed that airborne viruses exist in the form of agglomerates that increase the particle size x2-x3.

particle sizes and air filtration clearly


The best option is an elastomeric (rubber) full face respirator with a HEPA filter on board.


Well, or if not full-face, then at least a regular filter with the same HEPA filter + adjacent glasses, such as those in the picture:


or such, cheaper, simpler - aka chemist glasses


In my channel I dumped a picture with an approximate list of suitable masks.

here she is


and even advised one of the readers to use a filter from a vacuum cleaner, like the ULPA VC6500, instead of a filter box. True, you need to think about how to attach this filter to a standard thread of a mask / half mask / gas mask. And so it’s quite an option, it will not save from toxic gases and vapors, but it will cope with aerosols with a bang.


As I wrote, initially N95 were more effective than regular rag three-layer masks (in the case of SARS coronavirus), but later studies have shown that they are not particularly effective. Those. ceteris paribus, the following series works: the three-layer cheapest mask -> four-layer surgical-> N95. Better look for a 3M HEPA respirator with 8233 or 8293 valve (in the channel in the picture). If there is nothing like this, look at ordinary respirators or masks, with anti-aerosol filters with a P3 protection level (according to 3M classification), they should by definition be HEPA-based.

By the way, it is worth noting that masks with class N95 are rarely in our stores, because this class is taken from the US NIOSH standard. Respirators manufactured in the Russian Federation are labeled according to EN 149: 2001 ( GOST 12.4.294-2015) Those. an approximate analogue of the American N95 will be class FFP2 (it holds ~ 92% of aerosols, blue strap), N99 - FFP3 (it holds ~ 95% of aerosols, red strap). Additionally, there may be marking NR / R / D = one shift / reusable / dustproof. By the way, instead of the strap, the color marking of the class can carry an exhalation valve (red = FFP3). In general, a comment for those who are "looking, but can not find." Take at least masks with replaceable cartridges designed to work with paintwork materials (paints, varnishes, etc.).

In the official guidefrom 3M, for the choice of masks for health workers dealing with viruses, disposable respirators of the type 1863 (without valve), 1873V (with valve), 1883 (closed valve), 8835 (with valve) and reusable half mask 7501 (02/03) with replaceable filtering figures 6035 P3R cartridges. It is possible that such articles in your city may not be available. Then you can watch FFP3 (with red valves / straps) masks 9163V or 9332+. Please note that in the pictures in the attached document, people together with respirators use sealed goggles, like inexpensive ones manufactured by SOMZ 3NG-1 .



About the disinfection of used masks. After a day of work / wearing, it is advisable to sterilize the mask. The most “gentle” method - I don’t even advise sterilization with gamma rays, but you can boil / fry in the sterilizer. Temperatures of about a hundred degrees to polymers / elastomers will not cause harm to masks. You can boil a stream of steam (at least from an iron with a water hammer), avoiding getting on the filter.

PS By the way, sneezing and coughing is only in a handkerchief or in a bent elbow. Having sneezed in the palm, as a rule, the right one, we then grab hold of everything, shake hands with each other and thereby spread the infection even more than if we simply sneezed into space.


I’m ending here, like I collected all the most frequently asked questions by subscribers. Well, traditionally I advise you not to wait for an article on the Habrr, but to subscribe to my personal "mainstay of civil defense" and read everything in InstantView :)

PS
, « !».



Sergey Besarab (Siarhei Besarab)

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