COVID-19 Emergency - Using UV Lamps to sanitize Face Masks overnight - Page 1
Forum section: electronics / projects

author: Houseman
author_rank: Regular Contributor
timestamp: March 16, 2020, 05:07:48 pm
content: Hi all forum.I’m Steve writing from Milan in the north of Italy where the Covid-19 emergency is by far the most significant here than in other parts of Italy.As you may know (what happens in all Europe) we have a shortage in the supply of the non-reusable FFP3 face masks and the ones only available are used and reused for days even more than the datasheet suggests.Here doctors are even forced to work using simple tissue dentist masks.Having a wife that is a doctor I am wondering if using technology I could avoid in some ways the danger of reusing the same mask over and over maybe touching her face with a contaminated mask.So I was thinking building her a 222-nm far-UVC light lamp in a box, where she can put the mask after use and being sanitized during the night.I have read about Far UV lamps and the capability to kill germs and viruses:Here an article on pubmed:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5807439/I am asking if you think it is a good choice other than maybe change the internal carbon filter.So I would like, if possible, start a thread in order to discuss and maybe be helpful also for other people and other countries since we have seen the pandemia is spreading worldwide and it will last for months.Best regards and thanks.Steve

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 16, 2020, 05:26:08 pm
content: https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/2019-novel-coronavirus-myth-versus-factnormal mask is likely not to protect you at all, you are more likely to get covid through your hand, skin or cloth contact. always wash your hand when you think you touched contaminated area, and your face too if someone sneeze or cough on your face, dont poke your eye, mouth nose with unwashed hand. be safe.

author: SuzyC
author_rank: Frequent Contributor
timestamp: March 16, 2020, 05:27:19 pm
content: UV will kill bacteria but might also damage the mask fabric by ozone attack.Why not a quick solution: dip/spray with > 64% C2H302 and then hair-dryer dried?The Covid-19 Corona virus is encased in a lipid (a fatty cover) that is quickly dissolved by ethanol.

author: mzzj
author_rank: Super Contributor
timestamp: March 16, 2020, 05:34:54 pm
content: I'd suggest overnight in 60 degrees oven, sauna or other improvised heat source.CoV is similar to Ebola aka "enveloped virus" and should be reasonably easy to destroy.https://www.cdc.gov/vhf/ebola/clinicians/cleaning/ebola-virus-survivability.html60 degrees or even hotter 80C? 100C? shouldn't be a problem for the mask material itself.Note that this is 100% unproven and non-professional advice but..

author: Stray Electron
author_rank: Super Contributor
timestamp: March 16, 2020, 05:36:40 pm
content: Steve,I've been wondering the same thing. Germicidal UV lamps operate at the same wavelength as EPROM erasers I believe and I have a pile of old EPROM erasers here. The problem with UV is that it doesn't penetrate and it doesn't go around corners so it's only effective in direct line of sight. I looking into using UV sterlization when I had a MRSA infection several years ago and it appeared that it would need several hours of direct exposure at close range in order to deal with most bacteria. I have no idea regarding viruses.OTOH I'm also wondering if used masks could be washed, dried and reused. A solution of Clorox and water would almost certainly kill the virus but might be to harsh on the mask. I would think that a Hydrogen Peroxide or alcohol solution would be effective but won't damage the masks. Drying them in a warmed or hot, vacuum oven would be the fastest and would probably help kill any remaining bacteria or viruses.Ozone would probably also be effective in killed any viruses and UV lights usually generate a ton of ozone. Ozone would also penetrate the fabric of the masks. I have a large commercial HEPA air filter that has two germicidal UV lamps in it and it does generate some ozone. Anytime that I get old musty books or other smelly items, I set them on top of it and let the air/ozone blow around them and it always kills the odor. An old LASER printer that emits ozone will do the same thing.

author: jfiresto
author_rank: Frequent Contributor
timestamp: March 16, 2020, 06:05:19 pm
content: Formaldehyde gas will also kill the coronavirus. You can use paraformaldehyde crystals as the generator. It is one method for sterilizing operating microscopes. In an air tight box – a must – the crystals should last for months.

author: Bud
author_rank: Super Contributor
timestamp: March 16, 2020, 06:44:33 pm
content: Quote from: Stray Electron on March 16, 2020, 05:36:40 pmPeople restoring vintage computers using retrobrighting technique reported that covering the inside of the container with aluminum foil produces even coverage of UV light because of reflection. Makes sense to me.

author: Siwastaja
author_rank: Super Contributor
timestamp: March 16, 2020, 06:54:55 pm
content: I agree that heat should be easier to implement and more reliable in disinfecting the whole mask, not only the surface where the light hits. Try oven.

author: duak
author_rank: Super Contributor
timestamp: March 16, 2020, 07:06:20 pm
content: I have been thinking about this too. New masks would be better. Used masks could become a infection source for anything nasty that grows on them. I would expect that irradiating the masks with UV and then vacuuming them would not hurt.UV lamps have been used in HVAC (Heating Ventilation Air Conditioning) systems for a number of years. We have a central heat pump that I added a UV lamp to. After over 10 years, the heat exchanger seems quite clean even though in the summer when it's cooling, it is covered with condensation. The refrigerator, on the other hand sometimes develops a bit of mold in the condensate pan.Good luck to all,

author: Bud
author_rank: Super Contributor
timestamp: March 16, 2020, 07:54:07 pm
content: Quote from: mzzj on March 16, 2020, 05:34:54 pmSpeaking of which, I recently happen to modify the egg incubator (that I use for temperature drift testing) from 12V DC to AC power. Got a little cute MeanWell caged power supply which fit perfectly inside and replaced the DC power jack with a normal AC socket. Incidentally, the max temperature that can be set is 60C. Should things escalate, can be used for mask baking.

author: Stray Electron
author_rank: Super Contributor
timestamp: March 16, 2020, 08:03:26 pm
content: I wonder how much I can get for my old UV EPROM erasers/virus killers on E-bay?

author: Stray Electron
author_rank: Super Contributor
timestamp: March 16, 2020, 08:12:04 pm
content: Quote from: jfiresto on March 16, 2020, 06:05:19 pmChlorine Dioxide works well too. Good luck getting any if you aren't the Government! ClO2 is what they used to disinfect the entire US Congress building when they suspected it was infected with antrax. I expect that pure chlorine gas would also work but not many people want to work with that.

author: StillTrying
author_rank: Super Contributor
timestamp: March 16, 2020, 08:17:41 pm
content: Would microwaving the masks for a few seconds or more work.

author: Circlotron
author_rank: Super Contributor
timestamp: March 16, 2020, 08:21:45 pm
content: Quote from: Stray Electron on March 16, 2020, 08:03:26 pmAbout 1 roll of toilet paper.

author: Gyro
author_rank: Super Contributor
timestamp: March 16, 2020, 08:32:22 pm
content: Good old fashioned pressure cooker? - It's about as close to an autoclave as you're going to find at home.

author: mzzj
author_rank: Super Contributor
timestamp: March 16, 2020, 09:09:54 pm
content: Quote from: Gyro on March 16, 2020, 08:32:22 pmWorks but probably 400% overkill and possibly damaging to the masks.

author: thm_w
author_rank: Super Contributor
timestamp: March 16, 2020, 10:01:41 pm
content: Quote from: StillTrying on March 16, 2020, 08:17:41 pmFew seconds is not enough, a minute or two should be. But the problem is any sort of conductive element will cause havoc in the microwave, so you'd want to very careful. Think staples, reflective ink, etc. carbon filters might be an issue as well?https://link.springer.com/article/10.1007/s11434-014-0171-3https://www.tandfonline.com/doi/full/10.1080/0307945042000205874

author: Gyro
author_rank: Super Contributor
timestamp: March 16, 2020, 10:15:35 pm
content: Quote from: mzzj on March 16, 2020, 09:09:54 pmI'm not sure about overkill, a domestic pressure cooker it would probably be hard pressed to reach the required 130'C. Remember the mask would only be exposed to steam, not the boiling water. It would probably be a lot more gentle than dry uneven heat in a microwave.

author: iMo
author_rank: Super Contributor
timestamp: March 16, 2020, 10:19:31 pm
content: Hopefully you all distinguish between a "face mask" and an "FFP3 respirator".

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 16, 2020, 11:17:38 pm
content: If it's sunny in your area, just leave the masks in a car parked outside. You'll be surprised how good of a solar collector a car is even on cooler days.

author: ivaylo
author_rank: Frequent Contributor
timestamp: March 17, 2020, 05:02:41 am
content: Quote from: NiHaoMike on March 16, 2020, 11:17:38 pmCar windshields filter UV though (unless you are talking about heat generation)...

author: twospoons
author_rank: Frequent Contributor
timestamp: March 17, 2020, 05:24:08 am
content: The problem with UV is shadowing. Heat or an alcohol soak would be better as they will penetrate the cloth, where UV will only disinfect the outside.

author: rdl
author_rank: Super Contributor
timestamp: March 17, 2020, 05:43:18 am
content: Intensity of any local source of UV light is going to fall off rapidly. I'm not sure you'll be able to to kill much of anything. Chemical or heat sterilization is probably best.

author: mzzj
author_rank: Super Contributor
timestamp: March 17, 2020, 06:01:18 am
content: Quote from: Gyro on March 16, 2020, 10:15:35 pm130 degrees C is required to make sure something like surgical equipment in hospital is 99.999999% free of ALL pathogens. We are now interested mostly killing some wimpy viruses, not bacterial spores or prions.And even less than perfect result is better than nothing when you are in nearly war-like situation like Italy.If 60 degrees is good enough for Ebola I see COVID no different.

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 17, 2020, 06:58:14 am
content: Quote from: imo on March 16, 2020, 10:19:31 pmyes all the replies are a pile of bullshit, some will just destroy the mask, other will make it toxic or not provide any sanitationscientific literature (use proper search engine on the net to find that) proves that both ethanol and isopropanol destroy the capsid (the protein shell of the virus) in 30 seconds

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 17, 2020, 07:14:23 am
content: Quote from: Houseman on March 16, 2020, 05:07:48 pmboth ethanol and isopropanol have been proven to kill the virus in 30 seconds (use pubmed or other reliable search engine to find scientific literature)unlike ethanol, denaturated isopropanol doesn't stink and doesn't stain and in few hours evaporates completely (I tested that on my FFP3 mask)isopropanol is widely used in hospitals but you can still find it easily on the webJust yesterday I ordered another 5 liters supply fromhttp://www.antichitabelsito.it/alcool_isopropilico.htmso put isopropanol in one of those fridge boxes with airtight lid (PP or glass - doesn't matter) and leave the mask inside for a few minutes, than take it off, close the lid to reuse the solvent other times, and let the mask dry while you sleep.

author: hendorog
author_rank: Super Contributor
timestamp: March 17, 2020, 07:58:36 am
content: Since this is an electronic forum - what about RF at a resonant frequency which destroys the virus?I found this article where about 60GHz was effective for their sample, but its a bit old.https://www.livescience.com/7472-kill-viruses-shake-death.html

author: PartialDischarge
author_rank: Super Contributor
timestamp: March 17, 2020, 09:07:55 pm
content: I personally find the UV light idea appropiate and easily doable given the small size and certain transparency in the filter materialhttps://youtu.be/SqytOuYfsnA

author: Buriedcode
author_rank: Super Contributor
timestamp: March 17, 2020, 09:51:36 pm
content: I'm not sure I've seen it mentioned here, but 70% isopropyl alcohol (rubbing alcohol) is more effective at disinfection than 80%+. Although I vaguely remember this being the case for bacteria, unsure about viruses.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 17, 2020, 10:31:11 pm
content: i find its funny when somebody or WHO? suggested that UV lamp should not be around bare skin. people go to beach to get sun tan. baby will get uv lamp treatment if found jaundice (or what?) darker people (which indicates more exposure to UV) are usually much resilient and stronger. and just yesterday, i fixed our front gate due to broken retainer by welding it again and now i have skin rash, tomorrow i expect some dead skin peeling off.. for countless number of time already... free sterilization in the process i guess, and new skin too.. my uv lamp (nail polish curer) that i used to cure solder mask or the uv lamp used in hospitals are nothing compared to that weld arc...

author: viperidae
author_rank: Frequent Contributor
timestamp: March 17, 2020, 10:45:59 pm
content: Quote from: Buriedcode on March 17, 2020, 09:51:36 pmI heard it has something to do with the combination of water and alcohol that helps dissolve it. I think Dave said it on his recent hand sanitizer video

author: Buriedcode
author_rank: Super Contributor
timestamp: March 17, 2020, 10:58:27 pm
content: Quote from: Mechatrommer on March 17, 2020, 10:31:11 pmI'm not sure what your point is but chronicoverexposure to UV is a definite cancer risk. Acute UV burns have ionization damage. Regular UV burns are not just "oh well, it just toughens me up" - you are putting yourself at necessary risk.Also you are confusing multiple UV sources with different bands and intensities. The sun, isn't quite the same as welding flash, isn't the same as UV sterilization lamps. These have different spectrums, intensities, and the shorter waves don't go far in air. The UV used to "cure" epoxy glue was likely 395-405nm at low intensity. That is a far cry from the ~200nm germicidal lamps (that are also a couple of orders of magnitude more intense).Theraputic UV for skin conditions is carefully controlled, and won't be the short-wave type. You're effectively saying "this is light, and light is good right?".

author: LaserSteve
author_rank: Super Contributor
timestamp: March 18, 2020, 01:03:42 am
content: If the bulb is germicidal, mercury filled, with the clear fused silica envelope and not the black light blue, it radiates 254 nm. It possibly has a modest but energetic line near 185 nm depending on doping in the quartz, and will create localized ozone in some small amount . I spent years working in a polymer fiber lab, making biofibers, and I assure you that all three do a nice job on surface virus and bacteria, given enough time. We would have used the lamp to sterilize thin layers as they go down, not the finished product.The UV won't make it through to the core of the mask, but it will help break down most of the things that cause breath odors.UVA, not so useful, UVB and UVC, will help.A few one hour exposures will not harm the polymers very much, after all, one of the tests for the mask design should be degradation in sun light.I cant endorse reusing masks, but for most polymer and natural fibers not a problem for a few modest irradiations. The afore mentioned quick splash of 66 to 70% alcohol will do far better for you, but the UV will also break down many of the organics that cause odors.Any other solvent is a bad idea given that some fibrous materials are made with a solution deposition process. You do not want to remove any polymer binders that hold the fiber together.Good filters are designed to collect pollutants not just at the surface, but to down to a certain depth of the filter material. Hence the reason I state UV helps, but it is not a cure.My theory is anything is better then nothing, but you must have the right lamp. The lamp you want will quickly give you conjunctivitis, so you need an enclosure or polycarbonate goggles to protect your eyes. Nor do you want to breath in ozone.If the virus is in a dried organic solution, it might take a very, very long time to kill the virus.Better then nothing, but no where near 100% effective.Remember, the surgical mask is designed to stop big droplets. Usually it is to prevent the wearer from infecting others, not to protect the wearer from airborne materials.Steve

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 18, 2020, 04:36:39 am
content: Quote from: Buriedcode on March 17, 2020, 10:58:27 pmi dont say we can keep exposed to UV all day long. i'm trying to say, its not that bad as its said. i usually find people who get rid of the said item entirely because of some warning from authority. people dont get into electronics because afraid of lead poisoning. who got mad or lost temper control due to life long soldering? people dont buy items from china or quarantine their arrived parcel for few days (after few days already in shipping) because extra fear to virus. people dont get into electronics afraid of get killed by mains elecricity. and many more examples i cant point them all now. the point is, these warning, without adequetely educate people on what kind of risk, made people extra taboo. UV probably can make skin cancer, but for how long exposure? 1 day? 10 days? or 1 year continuos exposure? most people will think 1 hour exposure (or even less like 1 minute exposure) and you'll get cancer. this people dont know we walked everyday under the sun without getting anything bad or short lived, we may get some benefit as well, sun produces all kind of spectrums. but i dont say we should lay under the sun all day long for no reason, just do what we have to do for our benefit, no need to raise extra taboo or fear.

author: KaneTW
author_rank: Frequent Contributor
timestamp: March 18, 2020, 04:56:39 am
content: UVC is not something you should willingly expose yourself to, ever. It causes cataracts and skin damage at the intensities required to kill germs.There's research indicating that 210nm UVC is safe, but a) I'm skeptical and b) 210nm lamps are quite expensive.254nm UV (main mercury line) will damage you.I'm worried about the material compatibility of FFP3/etc masks to solvents. UV definitely won't cut it for sanitizing them.

author: Bud
author_rank: Super Contributor
timestamp: March 18, 2020, 06:58:08 am
content: So heat then appears to be the safest method both in terms of coverage and not damaging the material.

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2020, 07:55:36 am
content: Quote from: Mechatrommer on March 18, 2020, 04:36:39 amYou've completely missed the point. UV is a broad spectrum of electromagnetic radiation from 400nm, all the way down to 10nm. The 253.7nm radiation produced by germicidal lamps is not something any human is exposed to during their everyday life, because it is completely absorbed by the earth's atmosphere. Human skin has no defence against it, (darker skin is just as vulnerable as lighter skin) which is why one needs to be very careful not to expose themselves to radiation from a germicidal lamp.https://en.wikipedia.org/wiki/Ultraviolet

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 18, 2020, 09:22:37 am
content: weld arc covers whats absorbed by the ozone very well (200 to 400 nm)...https://www.ccohs.ca/oshanswers/safety_haz/welding/eyes.htmli'm one of many living souls to tell the tale... and if its real hazard devices (germicidal lamp), you wont be able to get it off the shelf anyway... what i saw on sales are for kitchen, bathroom etc where the vulnerable SWMBO usually at...

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2020, 09:29:15 am
content: Quote from: Mechatrommer on March 18, 2020, 09:22:37 amA welding mask is essential and it wouldn't surprise me if a germicidal lamp emits more UVC, than a welding arc. It's certainly on for longer, so would result in a higher exposure.QuoteWhat are you talking about? Hazardous items such as knives and bottled gas are widely available, as are germicidal lamps.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 18, 2020, 09:38:11 am
content: knives and bottle gas can be controlled and contained, hazardous lamp cant, much like nuclear radiation. and its not like we are going to put our skin 1cm from radiation at any moment. the fact that it is sold means its not as hazardous as its said in the warning. its similar to when authority gives warning "dont go outside you'll get caught by covid" so what do we do? ask our nurse/doctor wife to go home? some people will take this literally.

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2020, 09:52:08 am
content: Quote from: Mechatrommer on March 18, 2020, 09:38:11 amWhat have you been smoking?Germicidal lamps have to have safety warnings printed on them, because they are hazardous, but not as much has nuclear radiation. The UVC emission ceases, as soon as the lamp is switched off. The radiation can cause severe skin burns and eye damage, but is easily blocked by most clothing, wood, plastics and glass.Fortunately, it's not too difficult to mitigate the hazard from a germicidal lamp. Operate it a box or cupboard, with adequate seals to prevent the radiation from escaping and fit any doors with safety interlock switches to turn the lamp off, before the door opens enough to allow the radiation to escape.

author: KaneTW
author_rank: Frequent Contributor
timestamp: March 18, 2020, 03:27:31 pm
content: I'm buying UVC lamps every year for my pond. Many HVAC systems have them. They're off-the-shelf unrestricted items.

author: Bud
author_rank: Super Contributor
timestamp: March 18, 2020, 04:15:34 pm
content: Interesting study on survival of the virus on different type of surface materialshttps://www.nejm.org/doi/full/10.1056/NEJMc2004973Copper 4 hrsCardboard 24 hrsStainless steel 48 hrsPlastic 72 hrsI wonder what is the magic with copper....

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 18, 2020, 04:29:54 pm
content: https://en.wikipedia.org/wiki/Antimicrobial_properties_of_copper

author: Stray Electron
author_rank: Super Contributor
timestamp: March 18, 2020, 04:44:22 pm
content: Quote from: Mechatrommer on March 18, 2020, 09:22:37 amWrong. The old EPROM erasers all used germicidal UV lamps. I've pulled the bulbs out of over a dozen of them and they're all marked as germicidal lamps, and have quartz tubes and contain visible amounts of mercury.Previous posters are correct, these are definitely not eye-safe and the erasers all have interlocks to prevent them from being operated when the drawers are open, but you can take the tubes out and use them in a standard florescent fixture. I haven't looked in some years but the catalogs from the larger lamp companies used to all list germicidal lamps.

author: Gyro
author_rank: Super Contributor
timestamp: March 18, 2020, 05:23:35 pm
content: Quote from: Bud on March 18, 2020, 04:15:34 pmQuote from: SiliconWizard on March 18, 2020, 04:29:54 pmYes, the antimicrobial properties of copper, and other metals like Silver have long been known. Brass door handles and door plates were very effective in public buildings and hospitals. Unfortunately these days, everything has gone over to anodized Aluminium which, I think, is pretty much inert.The same with the traditional use of Linoleum flooring, which has natural and lasting antimicrobial properties.

author: james_s
author_rank: Super Contributor
timestamp: March 18, 2020, 05:37:22 pm
content: Quote from: Mechatrommer on March 17, 2020, 10:31:11 pm"UV" covers a broad range of wavelengths from just below the human visual threshold down into deep UV which are high energy photons, genuine ionizing radiation. Xrays/gamma rays are just photons, even higher energy than what is typically considered light. I do think it's a bit silly the amount of fear that the word "radiation" stirs and yet people deliberately go sit out in the tropical sun to irradiate their skin. Some is tolerable of course but UV exposure absolutely causes skin cancer at some levels and like any type of ionizing radiation there is no threshold known to be absolutely safe. Just look at what it does to many plastics and other materials. Leave them out in the sun for a while and they crumble to dust, pigments fade rapidly, the high energy photons blast apart molecular bonds.

author: james_s
author_rank: Super Contributor
timestamp: March 18, 2020, 05:49:23 pm
content: Quote from: Mechatrommer on March 18, 2020, 09:38:11 amMaybe things are done differently where you are but I would never expect something to be safe just because it is sold to the general public. Here I can walk into Walmart and buy a jug of hydrochloric acid, a bottle of MEK, a propane soldering torch and fuel, a hunting knife, a crossbow and bolts, insect poison, a box of shotgun shells and any number of other things including a germicidal UV lamp, no restrictions at all aside from showing ID to prove that I'm at least 18 years old to buy the weapons.The UV lamps have a warning on the box to avoid exposure to eyes and skin. Sure it won't hurt you to look at one for a few seconds but I wouldn't recommend making a habit of it, expose your skin to one for a half hour and you'll get a UV burn for sure. I've had the same thing happen arc welding where I had a patch of exposed skin somewhere and got a sunburn from the arc. The world is full of dangerous things, don't expect someone else to protect you from everything, that attitude is a cancer on society which has led to ridiculous warning labels plastered all over everything and far too many things people are not even allowed to do because someone is afraid of being sued.

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 18, 2020, 06:52:43 pm
content: Quote from: LaserSteve on March 18, 2020, 01:03:42 amI'm Italian like the original poster, it is just a matter of misunderstanding or if you prefer a translation error. Here we usually call mask a different kind of device made with thick fabric. It completely covers mouth and nose leaving no gap and is so thick the virus can't get through...here are some pictures(sorry it is in Italian)BTWI apologize to everybody for my rude comment of yesterday

author: LaserSteve
author_rank: Super Contributor
timestamp: March 18, 2020, 08:17:05 pm
content: Don't Laugh, My supervisor just sent a partial box and our last unopen box of N95 to the local hospital. At the emergent request of a surgeon alumni. I'm in the Midwest USA.That was our "Stash" for our critical personnel.Steve

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 19, 2020, 07:16:34 pm
content: Quote from: LaserSteve on March 18, 2020, 08:17:05 pmunfortunately there is nothing to laugh about... lots of people all dying all around the world... lots of medical staff too herethose personal protection devices are scarce all over the worldthey are increasing production or opening new factories, unfortunately it will take weeks before everybody gets all the due protection devicesjust stay at home, get out as little as possible, never get out even if you have few and mild cold symptoms, you might kill other people who is too weak to stand the virus

author: taydin
author_rank: Frequent Contributor
timestamp: March 19, 2020, 07:42:21 pm
content: I have bought a 15 W UV-C lamp armature. Used it today to radiate shipment packages I have received today. According to my research, this type of UV-C causes DNA damage in virii and bacteria in a matter of seconds (I'm no expert, this is what I read, so take it with a grain of salt).I basically hold the lamp towards the shipping package and because the light is behind the sheetmetal frame, I'm not exposed to the light. But here's what I have noticed: Within 30 seconds of turning the light on, there is a very slight smell in the air. I wondered what that is and researched. According to what I read, that is the smell of organic molecules breaking up and sulfur forming.I went over the packages for a total of maybe a few minutes and wasn't exposed to the light directly at that time. But I know what it is to be exposed to UVC. When I first bought my TIG welder, I did welding practice for a few hours with a short sleeve shirt. I had severe sun burn on my arms and chest that lasted for a week.This lamp is 15 W. There were also 30 W models available, but they were too long (90 cm), so I opted for the shorter one with less power.

author: Zero999
author_rank: Super Contributor
timestamp: March 19, 2020, 09:35:14 pm
content: Quote from: taydin on March 19, 2020, 07:42:21 pmThe smell is due to ozone being produced when oxygen in the air is exposed to short UV wavelengths. Ozone is also an antiseptic so might be partly responsible for the sterilising effect of the lamp.

author: Stray Electron
author_rank: Super Contributor
timestamp: March 19, 2020, 09:35:34 pm
content: I came here to post a similar story. I dug out a box of old EPROM erasers that I had and took a look at them. They are marked as "shortwave UV 254 NM" (Nano Meters) so theseareUV-C germicidal lamps. The nice thing about these is that were apparently original built to observe fluorescence in mineral specimens and have a window in the case and a another case with a sliding drawer was bolted to it. Remove three screws and the second case with the EPROM drawer and half the shell of the first case lift off and reveal the lamp in it's holder. The Start and Off push button switches and the power cord are part of the case that remains so it's ready to put to work.The model on these is a Model DE-4 EPROM Eraser made by Ultra-Violet Products Inc of San Gabriel, Ca. They're rated at .16 Amps at 115VAC so the tubes are probably 15 Watts or so. These were a popular device back in the days when everyone used EPROMs.Here is a picture from E-bay of what one looks likehttps://www.ebay.com/itm/UVP-DE4-Eprom-Eraser-08H9RM/184214895527?hash=item2ae4103ba7:g:TOMAAOSwlNpecPCXWhat you smell is probably ozone and not a sulphur compound.

author: taydin
author_rank: Frequent Contributor
timestamp: March 19, 2020, 09:55:00 pm
content: Quote from: Zero999 on March 19, 2020, 09:35:14 pmAccording tothisonly UV light with a wavelength less than 200 nm will create ozone. My lamp is the standard 254 nm germicidal lamp.

author: Zero999
author_rank: Super Contributor
timestamp: March 19, 2020, 09:59:46 pm
content: Quote from: taydin on March 19, 2020, 09:55:00 pmSome do. According to the link you've just posted:QuoteDid you buy that lamp from UVR or was it from somewhere else? If it has a plain undoped quartz tube, then it will pass 185nm and produce ozone.

author: taydin
author_rank: Frequent Contributor
timestamp: March 19, 2020, 10:05:43 pm
content: Quote from: Zero999 on March 19, 2020, 09:59:46 pmIt's not from UVR. It's a chinese product, LIGHTEX. Nothing shows up when I search for it, so can't tell its construction.

author: Zero999
author_rank: Super Contributor
timestamp: March 19, 2020, 10:59:12 pm
content: Quote from: taydin on March 19, 2020, 10:05:43 pmThen it probably does produce ozone, hence the smell. The air would have to be very dirty and polluted for reactions with sulphur to occur, so much so, the air would already be very smelly to start with.

author: james_s
author_rank: Super Contributor
timestamp: March 20, 2020, 06:11:21 am
content: Even a lamp that does not produce much light of such short wavelength may still manage to create a bit of ozone, it can be smelled in extremely small concentrations. My hot tub has an ozone generator that uses a small UV tube which is made of quartz.

author: taydin
author_rank: Frequent Contributor
timestamp: March 20, 2020, 09:44:35 am
content: Quote from: Zero999 on March 19, 2020, 10:59:12 pmThat makes sense. The smell wasn't like a foul odor that is typical of sulphur anyway, so it is probably ozone.In an FAQ that I read it says that the ozone will help killing germs that are not in the direct light path, so the ozone will actually complement the UVC light.https://www.americanultraviolet.com/uv-germicidal-solutions/faq-germicidal.cfml

author: Gyro
author_rank: Super Contributor
timestamp: March 20, 2020, 09:58:04 am
content: You can always get a robot to do it... and the rest of the room (UV-C):Quotehttps://www.bbc.co.uk/news/business-51914722I hope they use PIR sensors as well as a warning voice!

author: najrao
author_rank: Regular Contributor
timestamp: March 20, 2020, 12:23:15 pm
content: I am an old man stuck at home with only the woman I married 50 years ago. Neither of us is infected, so far as we know. I live in Bangalore, India, which has very low incidence of the virus infection just yet.Hand sanitizers are in short supply. But I have a large hoard ofisopropylalcohol, 99+% strength which I use to clean pcb's and assemblies. Would it work as well as ethyl?Let me have a quick reply please, thank you.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 20, 2020, 12:35:37 pm
content: soap and water for 20 seconds is all it takes, probably much more effective, save you IPA for the worse later... its good if you have 1 ton xray machine that can kill anything but... why complicates things during this hard time? you can watch people dying while trying to build or wait for the order to complete/arrive.

author: Gyro
author_rank: Super Contributor
timestamp: March 20, 2020, 12:50:23 pm
content: Quote from: najrao on March 20, 2020, 12:23:15 pmIsopropyl (IPA) is actually what they use in the medical environment and hand sanitizer. I think the normal concentration is 60-70%so you could let it down with water and maybe some liquid soap (to make it lather).

author: fcb
author_rank: Super Contributor
timestamp: March 20, 2020, 12:56:02 pm
content: Quote from: Gyro on March 20, 2020, 09:58:04 amI've seen one of these robots up-close and also under test.Essentially they are just a bunch (Philips) UVC tubes. 99.8% of the electronics, software and smarts are about detecting when someone has walked into a room unwittingly, remote control and IoT wank.They will ruin your eyes VERY quickly. I suspect they will also destroy alot of plastics used in the ward with more than occasional use. Also, these are used AFTER you have already cleaned a room.

author: Zero999
author_rank: Super Contributor
timestamp: March 20, 2020, 01:02:05 pm
content: Quote from: fcb on March 20, 2020, 12:56:02 pmIt does seem expensive. It would be much cheaper to add some germicidal light fixtures (not expensive, just ordinary fluorescent tube fittings, with germicidal tubes fitted) to the room, with a PIR and interlocks to shut them off if anyone enters the room, when they're on.

author: fcb
author_rank: Super Contributor
timestamp: March 20, 2020, 03:43:58 pm
content: There would be some benefit in moving the unit (robotic) - this would lower shading. Probably more cost-effective to put several static units in.

author: Buriedcode
author_rank: Super Contributor
timestamp: March 20, 2020, 05:32:28 pm
content: Quote from: najrao on March 20, 2020, 12:23:15 pmWashing hands with running soapy water is better than using hand sanitizers - because you're removing oils that help the virus stay on the skin. Warm/hot water is preferable as this helps the soap grab the oils. But IPA will disinfect if its between 50 and 90% concentration, hence the 70% figure floating about on the web. So thats handy for surfaces, the 70% concentration also slows down evaporation, because IPA and other alcohols don't "instantly" kill viruses, it takes time.https://www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 20, 2020, 05:37:50 pm
content: Proper washing is better, but alcohol-based hand sanitizers are certainly better than nothing when/where you don't have instant access to anything else. Like with masks, it's again all about lowering the risks, not making them disappear entirely.

author: Siwastaja
author_rank: Super Contributor
timestamp: March 21, 2020, 04:38:36 pm
content: Quote from: najrao on March 20, 2020, 12:23:15 pmIt works, but you don't need it if you are self-quarantining. Just wash hands normally.Alcohol-based products are a good addition to periods between being able to wash hands if you can't avoid going to public places.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 21, 2020, 06:07:04 pm
content: The poor guy may still have to get out once in a while...I think you can make your own mixture with water and IPA to get about 70% alcohol mix, then add some liquid soap (very little so it doesn't make foam) to the mixture to make it more gel-like. Glycerin would be better though if you have any available.But quoting Wikipedia:Quote

author: Martinn
author_rank: Frequent Contributor
timestamp: March 21, 2020, 06:39:53 pm
content: COVID-19 has a lipid coat which is easy to destroy with alcohol, so a > 62% (IIRC) alcohol solution would do, up to 99% ethanol or isopropyl alcohol.However, killing bacteria requires a certain water content. Best stick to the 75% water content as in the WHO recipe.https://en.wikipedia.org/wiki/Hand_sanitizer

author: not1xor1
author_rank: Frequent Contributor
timestamp: March 21, 2020, 06:49:38 pm
content: Quote from: najrao on March 20, 2020, 12:23:15 pmit has been showed that isopropyl alcohol (ethanol too) does kill the viruses within 30 seconds, but somebody else suggested just wash you hands accurately with hot water and soap as that is as effective as alcohol and leave the alcohol for objects you can't clean with water

author: jfiresto
author_rank: Frequent Contributor
timestamp: March 26, 2020, 12:34:24 pm
content: Doctors scramble for best practices on reusing medical masks during shortage: "Referring to a paper published in the journal Annals of Occupational Hygiene in 2009, among others, the researchers compared and contrasted ... different methods for sterilizing N95 masks, many of which were ineffective."Two were, however: "70 C / 158 F heating in a kitchen-type of oven for 30 min, or hot water vapor from boiling water for 10 min...."

author: profdc9
author_rank: Frequent Contributor
timestamp: March 26, 2020, 01:10:50 pm
content: Alcohol unfortunately can not be used to disinfect masks. It destroys a charged layer in the N95 masks that attracts virus particles. I wrote up a proposal for building a UV sterilizer for mask a couple days ago. Anyone who is interested please E-mail me:https://drive.google.com/open?id=1wF4yYgSE1n0Jqewb8JdwosTRhx0X89wFThis is a Google Drive link.It is a difficult problem because UV can also potentially destroy the elastomers in the mask so that the mask no longer fits well on the wearer. There is also cumulative damage to the filtration capability. But it presently seems the most promising approach. A paper in 2015 studied this:W.G. Lindsley, S. B. Martin Jr., R. E. Thewlis, K. Sarkisian, J. O. Nwoko, K. R. Mead, and J. D. Noti, “Effects of Ultraviolet Germicidal Irradiation (UVGI) on N95 Respirator Filtration Performance and Structural Integrity,” Journal of Occupational and Environmental Hygiene, v 12., pp. 509-517 (2015).https://www.researchgate.net/publication/274090116_Effects_of_Ultraviolet_Germicidal_Irradiation_UVGI_on_N95_Respirator_Filtration_Performance_and_Structural_IntegrityThere's a crowdsourced actively maintained document of resources athttp://ppereuse.com/.Best,Dan

author: Zero999
author_rank: Super Contributor
timestamp: March 26, 2020, 01:33:56 pm
content: Quote from: profdc9 on March 26, 2020, 01:10:50 pmThe lamp mentioned in your proposal produces ozone, which is good because it will not just sanitise the surface, but penetrate more deeply. The downside is ozone can be more damaging to fabrics and elastomers.https://www.amazon.com/AGAWA-Ultraviolet-Disinfection-Sterilization-Germicidal/dp/B085CGGQFR/I wonder how good the cheap LED germicidal lamps are? The blurb for the one linked below says it doesn't produce any ozone, so no good for masks, as it'll only sterilise the surface. It's inexpensive, considering the price of discrete UVC LEDs from reputable distributors. I accept distributors have lots of overheads, but I'm cynical of really cheap things.https://www.amazon.com/dp/B085VWPT9C/ref=psdc_2314207011_t1_B085CGGQFR

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 26, 2020, 01:52:03 pm
content: Quote from: jfiresto on March 26, 2020, 12:34:24 pmWouldn't a kitchen oven, which is designed for much higher temperatures, overshoot badly? (That's a common problem seen when trying to use a kitchen oven for drying 3D printing filament.) I suppose if you get a "dumb" oven designed for 240V and run it on 120V it would work a lot better.Perhaps the simplest solution is to just put them in a box and just leave them for the 9 days or so (which is turning out to be quite conservative) it takes for the virus to degrade on its own. It would also be interesting to see how long it takes to destroy the virus at lower temperatures like 120F. (The 9 day figure was under near ideal conditions, at room temperature it's more like 3 days.)

author: james_s
author_rank: Super Contributor
timestamp: March 27, 2020, 04:46:40 am
content: Some kitchen ovens are better than others at regulating low temperatures. If you were willing to modify the oven you could install a PID controller to precisely control the temperature at any level you want.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 27, 2020, 05:36:58 am
content: Quote from: NiHaoMike on March 26, 2020, 01:52:03 pmthe simple trick is to undershoot the thermostat setting by a bit. but i dont think covid will be happy with this overshoot behaviour.

author: Zero999
author_rank: Super Contributor
timestamp: March 27, 2020, 09:13:51 am
content: Quote from: Mechatrommer on March 27, 2020, 05:36:58 amIf a kitchen oven does overshoot, I've never had a problem with it. I frequently use my oven on the 60oC setting to dry my shoes with no problems. I'd hope a decent oven will be able to leaven bread, on its lowest setting, without killing the yeast.

author: jeremy
author_rank: Super Contributor
timestamp: March 27, 2020, 10:43:35 am
content: Seehttps://www.nebraskamed.com/sites/default/files/documents/covid-19/n-95-decon-process.pdfAndhttps://m.box.com/shared_item/https%3A%2F%2Fstanfordmedicine.app.box.com%2Fv%2Fcovid19-PPE-1-1Stanford research article very clearly and explicitly states: “DO NOT use alcohol or chlorine based disinfection methods” for mask disinfection.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 28, 2020, 12:00:35 am
content: Quote from: Zero999 on March 27, 2020, 09:13:51 amBread dough contains a significant amount of water that allows it to survive a lot of overshoot just fine. Plastics, especially thin plastics, overheat easily as often seen happening from those trying to use a kitchen oven to dry 3D printing filament.

author: Stray Electron
author_rank: Super Contributor
timestamp: March 28, 2020, 01:30:14 am
content: Quote from: Zero999 on March 26, 2020, 01:33:56 pmFYI. Germicidal lamps emit 254nm UVC radiation. Usually they are mercury lamps and mercury emits both 254nm and 185nm radiation. the 185nm radiation is what generates ozone and the 254nm is what directly kills viruses. However some germicidal lamps use a doped envelope (aka bulb) that block 185nm so those lamps do not generate ozone. A moral of the story is that if you want ozone then make sure that you use a lamp that doesn't have a doped envelope. Depending on the doping agent, the envelope on a doped lamp may have a greenish cast to it if you look at it in daylight.

author: Stray Electron
author_rank: Super Contributor
timestamp: March 28, 2020, 02:31:23 am
content: Quote from: profdc9 on March 26, 2020, 01:10:50 pmDan, a few questions. Is that true of all types of alcohol? Also couldn't "alcohol" still be used to disinfect the non-N95 masks? The charged layer is activated charcoal isn't it? If so could the alcohol be baked or live steamed out of the charcoal layer? (Live steam is what is used to "activate" charcoal.)

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 28, 2020, 09:04:44 am
content: Quote from: NiHaoMike on March 28, 2020, 12:00:35 amhave you done that? looks like you experienced. i did it and yes the old filament stock i tried to dry sagged quite badly but not it become unusable (setting is something like 100degC iirc). the next roll i dried i reduced setting to 60degC and it works. filament brittleness gone and become usable again. for things like paper, tissue, mask etc... i dont think they will combust at 100degC, even if overshooted to say like 150degC.

author: Zero999
author_rank: Super Contributor
timestamp: March 28, 2020, 10:24:06 am
content: Quote from: Stray Electron on March 28, 2020, 01:30:14 amYes, that's true, germicidal lamps are made the same as ordinary fluorescent tubes, but with quartz and no phosphor, so the UV passes through.I was talking about newer UVC LED-based germicidal lamps. The ones I linked to looked very cheap. I also question their efficiency. The data sheets for UVC LEDs I've found have an efficiency of around 2%, which is miserable compared to the 30% offered by traditional mercury lamps.http://www.farnell.com/datasheets/2774752.pdfhttps://www.ushio.com/files/specifications/germicidal-low-pressure-mercury-arc.pdf

author: jeremy
author_rank: Super Contributor
timestamp: March 28, 2020, 10:55:43 am
content: FYI in that video he is using alcohol to clean surgical masks, not N95 respirators. The respirators are what is damaged by the alcohol.

author: jfiresto
author_rank: Frequent Contributor
timestamp: March 28, 2020, 11:27:38 am
content: Another sterilization method:using vaporized H2O2to sterilize N95 masks

author: Stray Electron
author_rank: Super Contributor
timestamp: March 28, 2020, 02:18:17 pm
content: Quote from: Zero999 on March 28, 2020, 10:24:06 amI understand but my point is that some 254nm lamps use doped envelopes so they won't pass 185nm and are incapable of creating ozone. If you want ozone then you must use lamps that haveundopedquartz envelopes.The plainglasslamps with phosphor are 366nm lamps that are used for generating black light for cosmetic effects. They're useless for killing bacteria or virus and also don't create ozone. They have a SLIGHT effect on bacteria and virus but their killing power is literally about 0.0001% of what a 254uM lamps is. I think they cover that in herehttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC3831650/

author: Stray Electron
author_rank: Super Contributor
timestamp: March 28, 2020, 02:43:47 pm
content: If you really want to play with a kickass UVC source then go find one of the old Mercury vapor street lamps. We played with them when I was a kid and the ones that we used were 400 Watt lamps and had a small mercury vapor lamp with an undoped quartz envelope inside of a larger plain glass envelope that contained phosphors. We broke open the outer envelope and removed it and just ran the inner lamps by itself. They emitted tons of 254um radiation and any florescent material without about 20 feet would glow BRIGHTLY. They would also give us sun burns if we run one for more than about an hour and they also generated a lot of ozone.FYI They have a negative resistance so they are supposed to be used with a ballast.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 28, 2020, 03:58:11 pm
content: Found this study linked in the comments:https://www.ara.com/sites/default/files/MitigateShortageofRespiratoryProtectionDevices_2.pdfQuote from: Mechatrommer on March 28, 2020, 09:04:44 amResults vary dramatically depending on the oven, based on what I have read in 3D printing groups. Some suggestions to improve chances of success include letting the oven cycle off before putting in filament and some even suggested turning the oven off but leaving the light on.I personally keep filament dry by putting it in a bag (mostly sealed but not completely) and leaving it behind my PC.Quote from: Zero999 on March 28, 2020, 10:24:06 amI think those LEDs are best used for small devices like self cleaning toothbrushes. They're also RoHS compliant although I recall lamps not for general illumination purposes are exempt since many such specialty lamps (UVC being one) have no feasible RoHS compliant alternative.

author: Zero999
author_rank: Super Contributor
timestamp: March 29, 2020, 02:40:38 pm
content: Quote from: NiHaoMike on March 28, 2020, 03:58:11 pmI don't see why UVC LEDs would be better for small devices. 3W E17 lamps are widely available and it should be possible to make small mercury lamps the size of tiny neon indicator lamps, just by changing the gas fill and using quartz for the bulb. The amount of mercury used is tiny. I remember people being concerned about the environmental damage from mercury from compact fluorescents lamps, but it was later found out that the amount of mercury emitted from the extra coal burned to power incandescent lamps, exceeded that by many times.I can see some advantages of UVC LEDs, over mercury lamps, such as not requiring a warm up time, more mechanically robust, longer life and an unlimited number of on/off cycles, but efficiency doesn't seem to be one of them.

author: X.G.
author_rank: Newbie
timestamp: April 01, 2020, 07:36:20 am
content: I had used an oven to be a face mask restorer .http://www.crystalradio.cn/forum.php?mod=viewthread&tid=1838490&extra=

author: Siwastaja
author_rank: Super Contributor
timestamp: April 01, 2020, 12:53:52 pm
content: I did look at some papers on this, and one advantage identified for the LEDs is that they seem to sanitize better per mW of output, compared to the 254nm mercury vapor bulbs. The reason is likely that the most effective sanitization wavelength range appears to be somewhere around 270-280nm, and 254nm is outside the optimum area, so the LEDs emitting at 275 or 285nm are a better match. Some numbers I remember seeing suggest a difference of maybe 2-3 times, so the final efficiency is still worse than the mercury vapor lamps, but not very much. Is 30% a realistic efficiency number for classical germicidal lamps? I remember seeing lower numbers. OTOH, with no heat-up time, any application requiring intermittent operation (like water or air filtration based on flow rate) benefits from the LEDs.Looking at the rate of UVC LED development, efficiency and price, maybe they break through in the next 5-10 years. It's likely this crisis puts extra funding on the UVC LED development.I found quite different requirements for the energy of killing viruses on surfaces with UVC. One study suggested 9J/m^2 or 14 J/m^2 for killing 90%, or 98% of the viruses, respectively. The latter being 1.4 mJ/cm^2, those pesky 10-20mW UVC LEDs might be appropriate for disinfecting more than just toothbrushes. They are still quite expensive, though; one 10mW LED clearly isn't enough to disinfect large area of surfaces or large volumes of air. But I guess there is a lot of difference based on how much material there is for the light to penetrate; for masks, it's useless, as discussed, because the UVC light would need to penetrate many millimeters of the material. A lot of energy is needed for this, likely damaging the material. Heat works better.I'm personally looking at using UVC LEDs in disinfecting airafterproper HEPA filtration. In this use case, there are no large particles that "shade" the UVC light and protect the viruses from the light.

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 01, 2020, 03:26:34 pm
content: Germicidal efficiency of UVC leds at optimum wavelengths is maybe 30% more effective than 254nm. Efficiency is still an order of magnitude worse.The requirements vary and also are not super easy to calculate, but you want a 254nm dose of ~130mJ/cm2 to reach the target for a 99.99% inactivation of even resistant virii. Standards require 40mJ/cm2.Specifically, this is not the power emitted from the bulb, but actually reaching the microorganism. This isn't a huge issue when disinfecting air, but gets more complicated when disinfecting water.

author: profdc9
author_rank: Frequent Contributor
timestamp: April 01, 2020, 04:26:36 pm
content: If there are any references for UV mercury germicidal lamp efficiency, please send them may way. The study I was referring to isHao & Han, Qiuyi & Zhang, Shanduan. (2013). “254 nm Radiant Efficiency of High Output Low Pressure Mercury Discharge Lamps with Neon-Argon Buffer Gas” Applied Mechanics and Materials. 325-326. 409-412. 10.4028/www.scientific.net/AMM.325-326.409.That is where I obtained by 30% estimate from.

author: LaserSteve
author_rank: Super Contributor
timestamp: April 01, 2020, 04:51:19 pm
content: This is in my State, using H2O2 aka Peroxide. They did the research four years ago. Their machine handles whole shipping containers of masks.https://www.battelle.org/newsroom/news-details/battelle-cleared-to-sterilize-n95-masks-at-max-capacity-operate-in-other-states-to-fight-coronavirus-ppe-shortage.Process is Vapor Phase Hydrogen Peroxide.Steve

author: Caliaxy
author_rank: Frequent Contributor
timestamp: April 01, 2020, 05:11:38 pm
content: Quote from: Buriedcode on March 17, 2020, 09:51:36 pmA very plausible explanation I heard for that is that alcohol evaporates faster at higher concentrations. Even though 95% alcohol is more effective per se than 70% (in destroying bacteria and viruses), it stays on surfaces for a shorter time, thus its overall efficiency is reduced. 70% seems to be the sweet spot. Of course, this only applies to disinfecting surfaces, it doesn't applies to disinfecting objects immersed in alcohol.

author: pipe2null
author_rank: Regular Contributor
timestamp: April 01, 2020, 05:38:41 pm
content: I have not been able to find COVID-19 specific engineering data, but some medical professionals have used data from SARS-CoV studies for sterilization guidelines.https://www.eevblog.com/forum/projects/covid-19-related-engineering-data-ftlog-data-only-please!/msg2992562/#msg2992562For SARS (similar to coronavirus):Heating less than 75 degree C is NOT sufficient to kill all the viruses."...it was completely inactivated at 75 ◦C in 45 min (Fig. 2C). Surprisingly, at both 56 and 65 ◦C the virus was inactivated at early time points but at 60 min a small amount of virus was detected."UVC (254nm) is effectiveat killing the virus much faster than heat, 6 - 15 min.UVA (365nm) has no effect.NOTE: If you are reading a study that has to do with UV, if they do not specify the wavelength used (nm), then you should greatly discount their UV related results...As far as reusing masks go, profdc9 posted a collection of info:https://www.eevblog.com/forum/projects/covid-19-related-engineering-data-ftlog-data-only-please!/msg2992912/#msg2992912Quote from: Siwastaja on April 01, 2020, 12:53:52 pmIf you found professional or academic studies on this, would you mind please posting them to the above-linked thread?

author: Siwastaja
author_rank: Super Contributor
timestamp: April 01, 2020, 05:42:17 pm
content: Quote from: pipe2null on April 01, 2020, 05:38:41 pmI found a few by simple googling. Just made my own napkin memo & calculations, didn't save the references, sorry. You should be able to repeat the googling and find even more than I did, though.

author: Caliaxy
author_rank: Frequent Contributor
timestamp: April 01, 2020, 05:46:35 pm
content: Quote from: profdc9 on March 26, 2020, 01:10:50 pmNice! Not sure how effective this is (what's the penetration of uv light through the mask's material?), but I have two suggestions:1. In your photo, the lamp is in the middle of the box and the mask on the left side, next to the wall. This way, the "dark side" of the mask (that sits in its own shadow) doesn't seem to get much reflected light. I suggest putting the light source by the wall and the mask in the middle of the box, maybe suspended from the lid.2. Remove the elastomers before the uv treatment, sterilize them with alcohol and attach them after the uv cycle. Thus, they won't degrade because of the uv light (they might, because of the alcohol but, hopefully, at a lower rate).

author: 1sciguy
author_rank: Contributor
timestamp: April 01, 2020, 07:53:50 pm
content: Every town has a dry cleaner. They use Tetrachloroethylene, which evaporates completely. Millions of women would complain if there was a residue on their intimate apparel. I would suspect that no virus or bacteria could live through such a bath. I can't say whether or not it would harm any other aspect of the material composition.

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 01, 2020, 10:25:54 pm
content: Ultraviolet Germicidal Irradiation Handbook by Kowalski and The Ultraviolet Disinfection Handbook by Bolton and Cotton are what I use as references. Primary sources are listed in the books.

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 01, 2020, 10:29:18 pm
content: Quote from: profdc9 on April 01, 2020, 04:26:36 pmfrom Kowalski's book above

author: pipe2null
author_rank: Regular Contributor
timestamp: April 01, 2020, 11:07:49 pm
content: @KaneTW: Do you mind if I repost the UVGI info in another thread? Most people don't care, but I've been attempting to collect reference info into one place/thread. I've seen too many posts where people pull numbers out of their backsides that don't line up with the reference info I've found so far.Since there are a bunch of people working on other angles/problems, I've been trying to figure out the UVC intensity and exposure time requirements to kill COVID-19 or at least SARS-CoV. I'm hoping that mathematically it's possible to stick a UVC light in a can, pipe air through it, and kill viruses fast enough to meet or exceed the peak airflow from breathing... With the info I have so far, it seems like it's possible, but I don't have enough tangible data yet.

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 01, 2020, 11:31:12 pm
content: Quote from: pipe2null on April 01, 2020, 11:07:49 pmGo ahead. The books I mentioned are used to design UV systems for air (e.g. in a HVAC system) and water disinfection. There's also (commercial, with free trial)http://www.uvcalc.com/which can be used to model reactors so that you get the required target dose.The required dose rate depends on whether you want to kill everything immediately or whether the system is circulating and a partial kill is fine. It also depends on whether there's a constant influx of new pathogens or not.There was a paper on the relevant disinfection kinetics but I can't find it again. I'll let you know if I find something.

author: helius
author_rank: Super Contributor
timestamp: April 02, 2020, 12:00:54 am
content: Interesting details about UVC lamps in air handlers. What about the ozone generated? Is it a safe level or is there some way of filtering it out?Would the UVC be more effective on the intake side (before the air filter, so microbes would be killed and then filtered), or on the output side where it could help to sterilize the evaporator coil?Quote from: taydinThere are also hand-held, battery-powered UVC wands that can be used to sterilize surfaces and objects (like mail or door handles).

author: pipe2null
author_rank: Regular Contributor
timestamp: April 02, 2020, 12:19:11 am
content: If you were going to choose one book over the other, which one would you go with? I'm hoping you'll say "Ultraviolet Disinfection Handbook" cause that will get delivered much faster...The idea I'm working from is an in-line UVC virus killer to sterilize exhaled air from covid positive people who are using CPAP/BiPAP/whatever. And if you happen to have a metal housing available, you could use same principle to sterilize inhaled air for a healthy person. You should probably be able to use plastic/PVC housing for exhaled air for a somewhat short term basis, but not inhaled air due to photo degradation of plastic, ie undiluted unhealthy fumes. So, target is "quick" kill with no recirculation. Due to variety of available UVC sources (or un-availability as it may be for some people), I'm attempting to create a reference design that is easily modifiable based on your available UVC source, or prove that the source is inadequate. That's the idea anyway. I have 3.5W, 60W, and 100W UVC bulbs of different geometries ordered and I'll have 2 of them within the week.Whether or not my idea works out, the most important thing is getting the right information so people don't hack something together out of desperation, think it's working, but the bulb is grossly inadequate, for instance.

author: Stray Electron
author_rank: Super Contributor
timestamp: April 02, 2020, 12:19:34 am
content: Quote from: helius on April 02, 2020, 12:00:54 amI already covered the first part of this. You can buy 254nm lamps that have a doped envelope that blocks the 185nm radiation so they don't produce ozone.Regarding the 2nd part, IMO the UVC source would be most effective on the dirty side of the filter since the virus should be trapped on that side of the filter. That means that to protect someone from the virus it needs to be on the intake side but for preventing an infected person from spreading the virus that it needs to be on the human side of the filter. However having the UVC on the human side of the filter could also expose the skin and eyes to harmful UVC radiation so the design would have to prevent that. Also if the mask is designed only to prevent spreading the virus and to only filter exhaled air and not inhaled air then ozone generation shouldn't be an issue and may actually be a benefit since it would help kill the virus. So it looks like you would need two different mask designs to best serve two different purposes.

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 02, 2020, 12:46:21 am
content: Quote from: helius on April 02, 2020, 12:00:54 amDoped UVC tubes generate negligible amounts of ozone-generating UV as far as I know (haven't concerned myself with air disinfection too much, only water).No idea about intake/outtake. Industry practice for HVAC seems to be to install them in the return duct, but more research is needed.Quote from: pipe2null on April 02, 2020, 12:19:11 amIt's been a while since I used this for my own research, but Ultraviolet Germicidal Irradiation Handbook appears to be more general whereas Ultraviolet Disinfection Handbook focuses more on water disinfection. You can try both out via libgen and see which one is more pertinent to your questions.

author: helius
author_rank: Super Contributor
timestamp: April 02, 2020, 12:49:41 am
content: Sorry if I wasn't clear, I used "air handler" as typical jargon for main HVAC appliance. The integration of UVC into a mask is interesting but probably too complex for me to consider.

author: profdc9
author_rank: Frequent Contributor
timestamp: April 02, 2020, 02:24:43 pm
content: The University of Nebraska protocol UV disinfection exposes only the front of the mask. There are some supporting studies to show that UV germicidal radiation is effective at disinfecting SARS and influenza. Because the elastomer band is held in by staples, removing the elastomer band would probably compromise the mask as it would tear it. Better just to tuck the elastomer band behind the mask when exposing it. Furthermore, the damage threshold to the band is typically about 5 to 10 times that of the mask layers.Quote from: Caliaxy on April 01, 2020, 05:46:35 pm

author: KaneTW
author_rank: Frequent Contributor
timestamp: April 02, 2020, 03:20:51 pm
content: There's a system using vapor phase H2O2 for disinfection that appears to not degrade the filter media (https://www.fda.gov/media/136386/download).

author: Caliaxy
author_rank: Frequent Contributor
timestamp: April 02, 2020, 06:58:43 pm
content: Quote from: profdc9 on April 02, 2020, 02:24:43 pmWell, not according to their currently published procedure:https://www.nebraskamed.com/sites/default/files/documents/covid-19/n-95-decon-process.pdfOr, at least, they don't mention it explicitly. However, they do show a diagram (page 4) and photos (pages 1, 12 and 15) of the sterilization room with two uv light sources (which they call "torches"), one on each side of the masks hanged on lines in between the torches. It makes sense to me, as the mask can be contaminated on both sides while manipulated (removed) and you would also increase the penetration of uv light if both sides are exposed. They do tuck the elastic bands on the inside of the mask, though.

author: profdc9
author_rank: Frequent Contributor
timestamp: April 04, 2020, 02:29:39 am
content: Quote from: Caliaxy on April 02, 2020, 06:58:43 pmI looked at their other presentation and didn't see both of those sources. So they are using two, I stand corrected. With their method, however, there is a wide variation in distance from the sources and so I think that would provide a lower dose to the masks on the edge of the row of masks. It would be better if they turned their torch towers horizontal to get more even illumination. If I interpret their diagram on page 4, the detector for the dose is at the wall. However, figure 11 does not appear to be consistent with page 4. Page 4 shows the masks on the left side and the two sources on one side of the masks, while figure 11 shows the masks between the two sources.You could place two sources in the box I suppose and the mask between them, or hang the mask from the top of the box and let the walls of the box reflect the UV and illuminate both sides.By placing the source in the middle and the masks on the edge, the dose can be evened out somewhat, especially if there are reflective walls so that more of the illumination can be diffused more evenly but then the mask must be flipped over to expose both sides. I think it is better to try to keep the dose even because the cumulative damage to the mask depends on the dose, and so if the dose is greater than required, the number of reuses is limited.

author: KeepItSimpleStupid
author_rank: Regular Contributor
timestamp: April 12, 2020, 06:14:08 am
content: The photo shows 2 levels of lines to hold the masks. That appears to be missing in the words.there is also a 7 fold safety margin. Based on the location of the sensor, it looks like more than.So, should I make one at home from a cardboard box lined aluminum foil and an HVAC UV-C bulb?They only get 3-5x, but they wear the mask the entire shift. I have a few N95, non health care masks 3M 8211 at home and a half-face non disposeable respirator.

author: UnaAllan
author_rank: Newbie
timestamp: July 07, 2020, 02:15:24 pm
content: I guess you can desinfect masks with the sanitizer or just wash it in the machine with high temperature

author: KaneTW
author_rank: Frequent Contributor
timestamp: July 08, 2020, 02:09:47 am
content: No. You cannot. That ruins the mask's protective properties (for a N95-type mask)

author: Zero999
author_rank: Super Contributor
timestamp: July 08, 2020, 12:42:35 pm
content: Quote from: hendorog on March 17, 2020, 07:58:36 amThat's not RF but light, modulated at 60GHz. Microwaves are absorbed too easilly by water to be effective. No details are given, but it's a much higher frequency (near infrared to visible) modulated with 60GHz. Anyway, it sounds like something which works in the lab but is of no practical use, at this stage.

author: Zero999
author_rank: Super Contributor
timestamp: July 30, 2020, 08:51:18 pm
content: Quote from: JamesM13 on July 30, 2020, 07:27:16 pmIt looks like a fake to me. Test it by putting a banana quite close to the LEDs. If it turns brown, then they're genuine UVC LEDs, otherwise it's fake.Sadly, most LED sterilisers are fake. That looks like a dodgy site. There are no safety warnings about any of there products, because they're all fake. Real UVC sterilisers emit dangerous radiation which can burn the skin and eyes. Fake UV sterilisers, emit UVA, visible violet, or blue light, which is safe, but useless for disinfection. Return it and demand a refund.

author: KaneTW
author_rank: Frequent Contributor
timestamp: July 30, 2020, 09:07:48 pm
content: UVC LEDs are like 2% efficient, and that bag claims to use 10W (5V/2A). .2W of UVC is way too little to get germicidal action on a surface in a reasonable time frame. Batteries will die before it does anything.

author: Zero999
author_rank: Super Contributor
timestamp: July 31, 2020, 11:23:55 am
content: Quote from: KaneTW on July 30, 2020, 09:07:48 pmOf course it's a scam. The website says they're an American company, but I doubt it.https://uv-sanitizerr.com/have-a-question/Perhaps a prominent YouTuber such as Dave or Big Clive, should do a video on this.

author: Simon
author_rank: Unknown
timestamp: July 31, 2020, 12:53:38 pm
content: scammer banned

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 31, 2020, 01:25:10 pm
content: I wonder why they don't salvage flyback transformers from discarded CRT TVs (should be fairly easy to find a lot that still work due to the sheer number) and just use an arc as the UV source. It would also generate ozone, so it would even be dual action sanitation.That said, I'm getting the impression masks are a lot easier to get now and just having a bunch of them to rotate through would probably be the easiest solution.

author: Simon
author_rank: Unknown
timestamp: July 31, 2020, 01:26:56 pm
content: You just wash the masks and have a few.

author: Zero999
author_rank: Super Contributor
timestamp: July 31, 2020, 02:27:51 pm
content: Quote from: Simon on July 31, 2020, 12:53:38 pmI'm very sorry for not reporting that post. I can't believe I was gullible enough to think they genuinely purchased the product and were happy with it. They were obviously a scammer, spamming and trying to con people.

author: helius
author_rank: Super Contributor
timestamp: July 31, 2020, 03:39:19 pm
content: Quote from: NiHaoMike on July 31, 2020, 01:25:10 pmTypically, you don't want to create a fire hazard in the course of sterilizing a pathogen that may or may not be present. A bit like cutting off your nose to spite your face.Air-arc electrodes have fast rates of erosion, combined with the fire issue mean they can only really be used under contant supervision by trained operators in asbestos fire proofed rooms. Which is exactly how they were used in classic cinema projection booths before the advent of the xenon lamp (as well as in other industrial settings).BTW, flyback transformers do not create high voltage on their own, they require oscillator circuits. So I don't think your suggestion even works economically.

author: KaneTW
author_rank: Frequent Contributor
timestamp: July 31, 2020, 05:12:26 pm
content: You can use undoped quartz mercury lamps if you want ozone. But, you don't really want ozone. It's a pain to deal with.The best method afaik is still vapor phase H2O2, but that's unfeasible for the home user.

author: bson
author_rank: Unknown
timestamp: July 31, 2020, 08:24:46 pm
content: Quote from: Simon on July 31, 2020, 01:26:56 pmIndeed. Or if it's a single use, mist it with isopropyl alcohol until wetted through, and leave to dry.

author: Buriedcode
author_rank: Super Contributor
timestamp: July 31, 2020, 08:46:43 pm
content: Quote from: bson on July 31, 2020, 08:24:46 pm*70% IPA

author: robca
author_rank: Frequent Contributor
timestamp: July 31, 2020, 10:48:02 pm
content: Quote from: bson on July 31, 2020, 08:24:46 pmActually, no, don't use IPA or EthanolAll the single use masks (esp N95) rely on electrostatic effects and alcohol (ethanol or isopropyl) removes the treatment. Also ruins the sealhttps://www.nih.gov/news-events/news-releases/nih-study-validates-decontamination-methods-re-use-n95-respirators.UV has a lot of problems, too (mostly: it doesn't penetrate deep into the fibers, and over time damages the materials usedThe best domestic method to decontaminate a single use mask is 10-15 minutes in a 70C oven.Safe, easy to do, and scalable. Can find plenty of articles on thisAlso, leave the mask unused for a few days in a dry location, and no virus will remain

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 31, 2020, 11:00:32 pm
content: Quote from: helius on July 31, 2020, 03:39:19 pmTrivial to make one with just the addition of a power transistor and a resistor, so easy I managed to do it in 6th grade. It doesn't take much power to make an arc that generates a significant amount of ozone, in fact keeping the power down greatly reduces the fire and electrode erosion problems.