The current situation has given closet germaphobes the world over a chance to get out there and clean the hell out of everything. Some of it may be overdone; we ourselves can cop to a certain excess as we wipe down cans and boxes when returning from a run to the grocery store. But sometimes disinfection is clearly indicated, and having an easy way to kill the bugs on things like face masks can make a big difference by extending the life of something that would normally be disposable. That’s where this quick and easy UV-C germicidal cabinet really shines.
The idea behind [Deeplocal]’s “YouVee” is to be something that can be quickly cobbled together from parts that can be picked up at any big-box home store, thereby limiting the number of trips out. You might even have everything needed already, which would make this a super simple build. The business end is a UV-C germicidal fluorescent lamp, of the kind used in clarifiers for backyard ponds. A fluorescent droplight is modified to accept the lamp by snipping off a bit of plastic, and the lamp is attached to the inside of the lid of a sturdy black plastic tote. The interior of the tote is lined with aluminum tape and a stand for items to be disinfected is made from a paint roller screen. The clever bit is the safety interlock; to prevent exposure to UV, the lamp needs to be unplugged before removing the lid. Check out the full build tutorial for details.
We can’t vouch for YouVee’s germicidal efficacy, but it seems like a solid design. If you have doubts, you could always measure the UV-C flux easily, or you could build a smaller version of this peroxide vapor PPE sterilizer, just to be sure.
91 thoughts on “Disinfect PPE On The Cheap With This Hardware Store UV-C Cabinet”
I’m afraid this is actually worse than useless for masks. UV-C requires line of sight. The filter medium requires a convoluted path. The convoluted path blocks line of sight.
If you use this on a mask, you could believe that the mask is now disinfected, while in reality it is harbouring nasties in its convolutions. This false belief could make someone treat contaminated PPE as clean.
Peroxide vapour, on the other hand will travel through the convolutions.
” it is harbouring nasties in its convolutions”….. therein is the *key* point… the only manner in which it would acquire those ‘nasties’, is if it were drawn in or deposited from exposure to a contaminated environment. Now, how is the specific (CDC agreed upon) transmission vector ? oh, that’s right coughs, sneezes – distributing the organisms in an aerosol spray…… so ergo, ‘common sense’ says – as long as John Q. Public stays the hell away from unsanitary folks spewing micro-organisms, they -should- be in the clear….. or better yet, perhaps the only folks forced to wear such masks should be the ones doing the coughing and sneezing…. not the rest of the healthy population… and closing down businesses to destroy the economy….. “smh”….
Except asymptomatic people will think they are in the -healthy population” and spread the virus.
And the ones who think that they only have a cold, couldn’t possibly be sick, this whole thing is a hoax, etc.
how do they spread it ? ….coughing / sneezing maybe ? …breathing those germs in ? .. touching a contaminated surface, then picking ones nose ? … just walking past a person a few feet away isn’t gonna do jack if they’re not emitting contamination….. normal breathing doesn’t count… “asymptomatic” ? who cares ? as long as they are not transmitting germs… it’s all good….
I normally practiced what our resident physicist did anyway (avoiding touching public door handles, walking far away from people coughing, etc)…albeit perhaps not as overtly
Coughing, sneezing definitely increases the amount and spread but even breathing is now considered to be spreading the virus. Asymptomatic people DO spread it.
DrBrandt: Everyone wearing a mask would be a price I’d be well prepared to pay to end this stupid lockdown which is wrecking our liberties, harming our mental health, and crippling the important parts (think small/medium businesses and supply chains) of our economy. We should be looking to scale up PPE production and recycling so te lockdown lovers haven’t a leg left to stand on. Then we can work on containing this rather serious (worse than regular flu, less so than 1918 flu) but not in-itself world-threatening virus, and containing the even more dangerous state tyranny it has spawned. Being of the anti-lockdown persuasion I support any technology development which can make steps towards restoring society to non-authoritarian functioning, it is things like this which can help stop the virus without wrecking everything we hold dear.Well done Deeplocal for helping make a step along the road to freedmo.
Noone is a “lockdown lover”, but when years of pandemic preparation (decades) are thrown away, and decades-old response team disbanded, manufacture of PPE outsourced to China, we are PUT in a position that lockdown is temporarily necessary to stop the spread. Look at South Korea’s response and success compared to ours- they reported first case the same day we did.
We had the same information as South Korea has had for 20 years now.
Immediate, therefore much-more-temporary shutdown, and immediate and widespread testing and tracing of cases which will allow a much shorter shutdown period.
So, if you don’t like lockdown, or our need to scramble for supplies, or scramble for testing our populace so we ca all get back to work, don’t blame the people who are saving lives by locking down.
50 million pop
1300 people per square mile
Deaths per 1M capita 5
Seoul – 45000 people per square mile
300 million pop
94 people per square mile
Deaths per 1M capita 20
NYC 29000 people per square mile
If only people coughing and sneezing are ‘forced’ to wear them, how will this actually be enforced? If somebody sneezes in my direction whilst not wearing one, I can always tell them “you should be wearing a mask” but I think I’d just prefer to wear my own too (just in case people don’t do what they are told to do or don’t know they are symptomatic until they sneeze at me). What you are suggesting seems similar to only asking people who know they are definitely HIV positive to use condoms.
I think you can see some light through most of the masks, so perhaps given enough time UVC would penetrate enough. But of course it is difficult to judge what is enough, and too much will damage materials faster.
The materials in question tend to block all but 5% or less, so you’d have to increase exposure time 20 to 50 times.
I agree, I think it’s likely creating an atmosphere adverse to bugs would be more effective.
Looking at the datasheet for this mask (3M 8210) suggests it can tolerate being stored at up to 30°C.
It’s tricky to know how long it would take to inactivate sufficient amounts of the virus but it seems surgical masks which are not identical to the above tend to support the virus for longer (https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(20)30003-3/fulltext).
Looks like there would be some value in “baking” stuff at 30°C to shorten the period it takes to make the item “safer”.
UV might still be helpful in quickly “cleaning” the surface.
“baking” at nearly body temperature? Sounds lovely.
That’s exrreme hotness.
What about freezing? If you drop it below 0 celsius for a few hours is that likely to denature the covid pathogen? Or dipping the mask into a high percentage alcohol solution and leavin to dry afterwards before wearing again? If either of these is effectve against this type of coronavirus then they would penetrate into the fabric where the UV cannot.
Alcohol causes degradation in the material, reducing it’s effectiveness. Don’t know about the freezing though.
In addition to degrading the mask, when the virus is exposed to ETOH (alcohol) in concentrations above 70-75% is actually less effective. I know that seems counter intuitive but the higher concentrations if I remember correctly sort of burn the outer layer of the virus leaving the damaging dna/rda unaffected and thus still virulent. I know I read that in a reputable paper somewhere but I can’t site it, also the data may have changed as studies improve etc.
Also, isn’t it true that UVC reflects off of no surface. Not even mirrors.
That’s a ridiculous assumption… and a myth.
If you want to reflect UVC the you need a mirror with a material on it known to reflect UVC, this means something like a front plated mirror with with perhaps some thin anti oxidization coating. Cheap mirrors use a back plating. You can certainly get mirrors engineered to reflect UVC.
Many mirrors especially old ones have a silver or aluminum backing… and this does reflect UVC. However, the glass material may not transmit the UVC if not designed to do so. And as I said an easy way around that is to use front plated mirrors… with a thin coating with high trasmissivity for UVC.
Another alternative might be glass engineered to transmit UVC but I suspect this would be more difficult.
Oh so wrong….. Only highly specialized electropolished aluminum can be used to reflect UVC. I have done extensive study on this and have test many different perceived reflecting materials, glass and polished mirrors included. They absorb UVC and do not reflect it.
Earlier reply didn’t show, in short that is a myth, silver and aluminum among other things reflect UVC, beyond that all you need is a layer on the front of the mirror that is UVC transmissive like a special glass or thin layer with the glass on the back of the mirror.
Different wavelengths of light absorb and reflect differently on the same material. For example, IR light reflects pretty well off of white boards. You can use one as an IR mirror. UV-C is no different in that some materials will act like mirrors for it while absorbing other wavelengths. It is not something you can “sense” until you try it. I don’t know if aluminum foil reflects UV-C, but it would not be hard to test.
Polished Aluminum reflects most wavelengths, including a good chunk of the UV spectrum.
The plastic in the aluminum tape would probably break down quick.
I was wondering about the efficacy of ozone generators. The goal would be to use it to sterilize fresh vegetable.
Before everybody jumps on me about the dangers of eating vegetables exposed to ozone I haven’t really done much research on this…I was just wondering.
Was thinking the same.
I have one for such purposes. For test I placed an overgrown pot of weeds inside a plastic bag with an ozone bubbler for ten minutes. I suspect a couple of minutes would’ve sufficed. It sucked the life out of the weeds. DON’T f around with ozone carelessly.
Having played with tesla coils and jacob’s ladders for years I’m not really bothered by the though of ozone exposure. After extended runs you can smell the ozone in the air. I kind of enjoy the smell.
i have bought them, hoping they will work
If it’s like my UVC lights, if the UV doesn’t kill it, the massive amounts of ozone it produces will. Be sure to have plenty of ventilation for your lights.
If it produces Ozone, it will do the job.
this is 100% correct. UV is really meant for stainless steel, flat objects like biosafety cabinets. It’s highly determined by the type of material you are exposing, all kinds of stuff, as well as the type of thing you are trying to kill. I would not recommend anyone try to use this as a hack to decon PPE without really testing it.
the UVC lamp would also generate ozone. if the ozone is confined in such a small space it should be able to permeate through the mask material. if ozone scars lung tissue, i would suspect it should harm the little nasties.
60°C for one hour is not anough!
Coronavirus can survive long exposure to high temperature, a threat to lab staff around world:
Important: do not expose your eyes to a UV-C lamp. It can cause retinal damage.
As well as damage to your cornea… since that will probably be the area taking most of the UVC energy… it causes cataracts.
UV can „clean” surfaces, but despite their relative thinness masks catch germs with their entire volume. I am afraid shining UV-C strong enough to penetrate fibers will destroy them after few sessions.
A safer alternative is to keep your PPE in a 40-50 deg C box or cabinet, and leave it there for a few days. Safe for the material and children, makes it dry so it doesn’t grow mold, and destroys the virus throughout.
There’s supporting evidence that this works, check page 5 of this Stanford report:
Its not a cure-all, as the masks mechanically de-grade per this:
Here’s an article and paper on the subject of disinfecting masks for reuse:
UV cleaning works well for some things. But not for others.
Just to reiterate what everyone else have already said, UV needs line of sight for it to work properly.
It can bounce a couple of times and still do a reasonable job, but this is not nearly enough to actually reach anywhere noticeable into a filter.
Using Ozone, or peroxide vapors will be more effective. Though, these can degrade other materials in the process. Like Ozone and rubber doesn’t play well together… But at least the rubber bands can be replaced if they were to wear out.
Though, UV can be used on other PPE, like gloves and the like. Or for anything where we only have surface contamination to worry about. UV can also be used to sterilize working surfaces.
All of you keep repeating line of sight…but nobody thinks about the ozone this chamber will inevitably produce? Personally I think THAT is the main mechanism of how this thing sterilizes and that actually exposing the object to UVC just causes unnecessary damage to it…
Ozone seems like a really good suggestion, definitely worth investigating. Might need the industrial grade generators though, not the little ‘air purifier’ ones that you can get off amazon. The problem might be with any rubber items that are connected to the filter (like maybe the diaphragm in the one-way check valve or the elasticated straps?).
Worst idea every. They will destroy masks doing this. They could be doing 24hr ethyl alcohol baths and hang dry them in a cycle. That method has been used for years. It doesn’t destroy the polypropylene. UVC degrades polypropylene very quick. Ozone is good for hard surfaces and air systems. But it is very reactive and will also breakdown the polypropylene.
Hydrogen peroxide seems like a good idea. Until you start to think about what it oxidizes into, H2O. The polypropylene used in N95 is hydroscopic, so the fiber mesh will swell and deform.
Really glad to see I’m not the only one seeing these flaws. Seeing this brought me hope. That some people are using their brains in the middle of all of this.
Please remove this entry. As every commenter has remarked, this will NOT work for masks. Since the lead photo is showing a mask someone reading this post without reading the commenters might think it’s an appropriate use. It’s not enough to say “we can’t vouch for YouVee’s germicidal efficacy” when you have been given every reason to believe it won’t work. It’s one thing to post dubious content when it has no consequence. This one could kill someone.
So you’d prefer there to be just the original blog post, but not the insightful comments brought by hackaday visitors?
No, it sounds like he’d like the blog post to be removed altogether, as not everyone is intelligent enough to question what they read or read others comments (which almost all point out issues) about it before steaming ahead with there own versions.
At the very least a bloody big message saying “this won’t work for masks or other porous materials” at the top, maybe flashing, is needed.
I agree 100%. @Editors this is disappointing that this is still up, for the clicks I presume. I would nuke this especially with the title. At a minimum i would change the title to “Backyar sterilization method endangers hacker” or something.
Up to you but I think this is a terrible thing to leave around.
Please see my post below. Or click this link: http://shorturl.at/pxIV1
It’s feasible, but you need to use an adequate dose to each side.
– Heimbuch and company contracted by the FDA to study UVC disinfection of N95 masks with 275 page article: https://www.ara.com/news/ara-research-mitigate-shortage-respiratory-protection-devices-during-public-health-emergencies
– Subsequent paper verifying efficacy: https://www.ajicjournal.org/article/S0196-6553(18)30140-8/fulltext
– University of Nebraska protocol for using UVC to disinfect N95: https://www.nebraskamed.com/sites/default/files/documents/covid-19/n-95-decon-process.pdf
– Lindsley’s article showing dosage required to cause mask break down is very high: https://www.tandfonline.com/doi/full/10.1080/15459624.2015.1018518
– 3M’s article stating that N95 fitlration is not affected by UVC: https://multimedia.3m.com/mws/media/1816576O/disinfection-of-disposable-respirators-technical-bulletin.pdf
Tell Dr. Rupp
Recently used a home oven on procedure/surgical masks for personal use. Was attempting the 70C for half an hour protocol. Oven’s lowest set point was 170F which is ~76C.. Preheated to 170F… put the masks in on middle rack on double bottom sheet (Didn’t wan’t them sticking to hot spots, tinfoil a regular pan if you don’t have one.) Checked with IR thermometer after they’d been in 5 mins, read 72C set a timer for half an hour… turned off oven when timer expired but let them cool off in oven… Masks looked perfect upon removal, no browning or discoloration, no seams falling apart, no shrinkage. Elastic seemed to be in good shape also. I assume they could have seen up to 80C during that period. So what’s the headline “Extra, Extra, oven goes to temperature it says on the control” or something. Just to say I am confident I managed to exceed the 70C for half hour protocol and not damage the masks. YMMV with other types, the N95s with exhale valves may have that distort, only have 1 of those and it’s not going in until it’s “used up”.
This. We’ve been doing it for several weeks using a cookie cooling rack for air circulation. To the level of microscopy that I’m able to use, I don’t see any fiber deterioration v. new masks.
UV is a really poor germicidal method for anything but a line-of-sight surface.
More information here: https://www.scph.org/sites/default/files/editor/facemask_shortage_0.pdf
If wearing a mask protects others from COVID…. the media has not caught on about N95 masks with EXHALE valves. These let coughing and sneezing aerosol and micro droplets leave unfiltered.
They definitely redirect and slow the stream though, you’re definitely not getting 8m/s though it into the air. It directs it down.
Yah, they are not recommended for known patients to prevent transmission, only to healthcare workers as best chance to keep from catching it.
(Which is what my open package, bought years ago ones are reserved for now, in case any of the tribe goes down with it and confined to bedroom, for others to care for them. No point wasting those going to stores.)
I just tape over the valve opening inside the mask, so I’m exhaling through the mask fibers. I don’t even notice a difference.
This will work because sound vibration passes through matter, if you look at the UV-C radiation as both sine wave and line of sight, you have sound light frequency vs visual light spectrum. To prove proof of concept, we need two tests: one using lead shielding and one without. Theoretically the lead shielded model will show no possible improvement and the one without will show change, but both tests need to be separated or the lead test be conducted in a lead cabinet thereby reducing the UV-C exposure.
If we apply the theory of sound resonance vs biological matter, we will see that the UV-C light will work without the line of sight mattering.
If you wish to dispute this, please refer me to the part where ions and neutrinos don’t pass through the Earth itself or where light energy doesn’t have sound spectrum resonance in of itself.
The very colours of our standardized colour spectrum representation of sound bandwidth frequency are the same!!!
Light and visual spectrum are the same as sound and audible frequency generation!!!
Therefore, 60Hz is 60Hz in colour as is in sound!
For all you egg heads out there that say this won’t work, at which point does the sound spectrum not pass through solid matter?
Bass frequency passes right through my body, so do shock waves from a grenade turning my brain to mush. Sound energy is used in deep earth penetration. So UV-C might not need to visually penetrate an article of clothing or a carbon fibre filament, but the sound spectrum has no choice from that spectrum to pass through it! Microphone drop…
You all been powned!
I don’t know where to start…light waves are different to sound waves is probably a good place, photons of light are blocked by being absorbed by the material or reflected by the material. If they are absorbed they warm up the object. If they’re reflected a little energy is lost to the surface but most energy is reflected away and the light wave continues. With sound waves when they hit an object they can also be reflected, absorbed or they can transited through the object and effect material on the far side. If they are reflected then the sound level with reduce in direct proportion to how much is lost to the reflection, if they are absorbed then the object will heat up, if they transit through some energy will be lost to the object.
Just because they are both waves (or at least light can be considered as a wave) and thus both have frequency, does not mean they behave in the same fashion.
Pressure waves moving through matter isn’t the same as photons traversing the electromagnetic field.
What you even want to prove with lead shielding is frankly beyond me. (other then the very clear association with radiation shielding, but gamma ray shielding is a very different topic. And a wildly different part of the electromagnetic spectrum.)
The idea that just because sound waves can travel through most matter rather “unhindered” isn’t really a case for light doing the same, just because light can be thought of as a wave doesn’t give light the same properties as sound. And bringing up Neutrinos and Ions isn’t really a valid point either.
Neutrinos are not photons, nor are they whole atoms “bumping” against each other. Neutrinos are a subatomic particle that has very little interaction with other subatomic particles. Meaning that it frankly doesn’t really know that our world even exists to be fair.
Ions also don’t easily travel through other materials, an ion is nothing more than a regular atom having a charge imbalance. (ie, having more or less electrons than what it has protons.) In other words, an ion has about as hard of a time traveling through stuff as any other atom. (Though, it is far easier to accelerate ions up to immense speeds than neutrally charged atoms.)
But as already outlined, sound waves are nothing more than pressure variations propagating through matter and have practically nothing in common with light.
I have 2 in 1 poorman solution ;) Old mercury light bulb with cracked glass bank for making PCB
but it’s producing really odd UV-C and I am using it for disinfect my FFP3 face masks now.
I verry similiar like this http://www.pcbheaven.com/projectpages/Hack_Hg_Lamp_to_UV_Light_/
i leave my mask and glove in it’s clear plastic case on the dashboard of my jeep. get’s plenty hot in the sun and saturated with UV. casual but better than nothing.
The UV that kills the virus is UV-C. Our atmosphere blocks out UV-C, so that is not helping you. The heat, on the other hand, is probably.
*quickly… The peak germicidal region straddles UVC and UVB, while effectiveness declines down into the UVA, which then requires increased exposure times.
Both a windshield and most plastic boxes will block a lot of UV also, so while a whole day of sunlight exposure gets in the neighbourhood of being effective, doing it under glass and most plastics won’t be. One common plastic that doesn’t block UV much is cling film/saran wrap of the non-recyclable type. Transmits 85-90% of UV, so you can cover a tin or box with that and put stuff in it. However as Dr N mentions, just the heat might do it.
Similar to SODIS(https://en.wikipedia.org/wiki/Solar_water_disinfection) which is popular in rural areas where water is stored in small <2L PET bottles, 3/4 full shaken up to incorporate air.
So long as it's not raining the water should be disinfected within 2 days (as soon as 6hours in ideal conditions).
Only concern depending on where you live that might get seriously hot?
Also, there needs to be a big warning that powering on a UV-C bulb, even for a few seconds can burn your eyes and skin.
I’m pretty sure that’s why there’s an interlock in the design of the sunbox, to prevent operator exposure
Surprised no stories about making filters on HaD, plenty of HVAC and air con units have N95 filters.
What about DIY airfilter boxes? Think I saw a tweet from China covered on HaD about this but not detailed builds
So why isn’t microwave radiation being used? They pass through most fabrics and organics. True they might not affect things the size of virus’ but they will affect the things the virus is on.
water molecules are way smaller than virus and still get affected. so it probably can work but it has to hit the resonance frequency of one of the molecules constituent of the virus, I guess
Im getting so sick of these coronavirus related builds.
Its a time where we do need things that work, but I am personally seeing this tear apart makers and hackers in my own community hackerspace, as some people step up and act like Messiahs and take over, berating people over what they see as technical inadequacies as makers constantly bicker on a hackerspace slack Channel at each other while people try to help in any way they can.
UV-C builds were the real tipping point for me. Some really horrible people came out of the woods on us at mine, just to shout down people even trying to build stuff like this.
It’s making me hate my membership and my city’s makers, and showing me the obnoxious knowitall messiah types who are bravely showing us that only 3d printing facesheilds can “save” people, and any effort to the contrary is “propaganda”.
This virus has brought out a real virus of asses in the maker community, some even on these forums.
It makes me angry and sad
Did you even consider that those “really horrible people” might be right, or did you not want to hear that. Lives are at stake with this, so perhaps you should check your indignation at the door.
Aaand that exact attitude is exactly what we get from these people.
I don’t need it here too.
Lets get this straight right now- with hundreds of people researching what works and what doesn’t- when the info from even the CDC at times was not current or even conflicting, suddenly everyone is a self professed expert, and people who are even trying to donate medical supplies, like sterile medical grade nitrile gloves, are getting this attitude from the next messiah in line maker.
I know damn well lives are on the line. What I don’t need is non medical professionals and armchair scientists berating me and others for speaking up about this.
The attitude of wanting to help is good- the toxic holier than tho types who are using their so-called expertise (that often seems to have materialized out of nowhere) to belittle others tired of asking how they can help is making me quickly not care anymore.
My space tried to have intelligent discussions about exact wavelengths needed in LEDS, best practices, a lot of really intelligent and some genius people there- and on here- but it has devolved to the loudest, most self important voices literally giving orders and insulting people at my space.
Here- knock it off.
I’m not commenting on any of these projects any further because of people with your attitude.
Oh, I see now. “Non medical professionals and armchair scientists” being berated by OTHER “non medical professionals and armchair scientists”. Got it.
Is it impossible to call out the obnoxious entitled attitude of rotten people who claim to be makers, and browbeat others with sarcasm and condescension? Is having the last snarky witty response all some people are good for?
I am no medical expert myself. I’m a machinist, with a degree in a foreign language. Not a virological expert from the CDC. I’d wager you aren’t either. And even they are still sorting out more advanced aspects of mass PPE sterilization. I’m not here to tell people stop discussing what will work and what wont.
I’m also not here to suffer through obnoxious trolling while people ARE dying.
We are supposed to come together to help human life, not berate and belittle other makers like this. We’re supposed to be better than this.
This is the very attitude that made me walk away from my own hackerspace. People acting like you, but much worse, who make me wonder if humanity is worth trying to save.
All that was left that wasn’t toxic in my country now boils into what little sanity was left, the community of makers. And now, even here, I begin to feel no hope.
Go save someone, if you can, please. You aren’t saving me from anything.
Lighten up Francis. :) We’re all scared. Thankfully when engineers get scared they try to build solutions. UV-C effect on a anything with DNA or RNA it can get to and at a certain intensity a d duration is well documented. Sanitizing masks may not be the right application for this gadget. But we’re all learning from the back and forth. At least this is plausible. I’ve not seen any suggestions about Antibiotics effectively treating viruses. I’m glad we have so many bright minds giving their time to things like this. And people like you making sure we know the dangers and limitations. What’s the alternative, waiting for a solution to fall from the sky. It ain’t coming. The ship is sinking and people are building lifeboats. Most of us have never built lifeboats before but at least we aren’t waiting around till the water reaches out feet.
i agree. try wat u want to try. best practices will come out of course. regardless of the nay sayers. be safe.
Here is the thing with UV-C sterilization.
It works perfectly for sterilizing work surfaces and other places with surface contamination. Since it will only reach things in direct line of sight. Ie, only the very surface of an object.
When cleaning a work bench, one should use UV-C as the very last sterilization step. Since any dust or gunk on the desk will shade the surface of said desk, meaning that those area’s aren’t clean.
An air filter is designed and built to be a maze for stuff to get lodged in. Ie, most contamination builds up within the filter itself.
UV-C won’t reach into the filter fabric. Ie, UV-C won’t sterilize it, and reuse of the filter can lead to unintentional spread of the virus, since the attempt at “killing” it were frankly inefficient for this application to start with.
Using UV-C for places where it is actually good is one thing. But air filters isn’t one of those things.
Why not bake the masks? Then you can do large batches at the same time too. All you need is a heating element, rtd, controller+relay, and an insulated box. 60 C should be enough to kill most anything and the mask material and band would be fine.
Bacteria tend to dislike warm temperatures. Since it can make many vital functions in their cell stop working.
Viruses on the other hand. Well, they are dead by definition. They have no vital functions that stops.
The only heat related death viruses has is protein deformation. (Boiling an egg is a classical example of protein deformation.)
But the temperature where this deformation happens at can vary wildly. Some proteins can survive just fine in 120C. While others deform already at 10C.
Not to mention, it is a large question how this even effects the virus in the end. The deformed protein might still do its job.
So heat isn’t always going to be a solution.
Though, testing is one way to find out. And I haven’t checked how the Corona virus reacts to heat, or how warm it needs to get and for how long. (Well, the virus will die if we toss the mask into an incinerator, but this has a side effect of loosing the mask too….)
In the end. Heat might work, it might not. It all depends on the virus and the thing one wants to sterilize.
Not to mention that the greatest enemy a virus has is bacteria. (Most viruses tends to get eaten up by bacteria. So a non sterile surface can actually be safer than a sterile one… But this is obviously a double edged sword.)
I do have a UV cabinet – Wabi Baby. But for masks, to prevent breakdown, I decided to have 4 masks and not worry about things. 3 days time between wearing them is probably is more than enough, but I keep some in my car and some at work. I don’t go shopping for groceries every day, so this is already overkill, but if I sneeze, the UV cabinet gets used
Please stop bickering, we’re in this together. I will try to shed some light on the issue, no pun intended.
I’ve collected notes on ~30 articles regarding PPE reuse, and I’ve posted it here http://shorturl.at/pxIV1
Heimbuch was contracted by the FDA and has a 275 page article discussing his results on UVC disinfection of N95 masks. UVC light can be used to disinfect N95 masks, the target dose should be 1J/cm2 to each side of the mask. Lindsley’s article showed that mask breakdown does occur, but at higher doses, well beyond the practical lifespan of the mask. Approx 70% of UVC light reflects off of aluminum tape. University of Nebraska (the Ebola scientists) created a protocol to mass disinfect masks using room UVC sterilizers, though their dose may be too low. If you want more details, the articles are in the link including the full text for most of them, and I’ve done short summaries on the ones I’ve skimmed/read.
Do not use ethyl/isopropyl alcohol on N95s, it reduces fultration by 50%.
Moist heat, dry heat, boiling in water, dipping in hydrogen peroxide may all work.
I forgot to mention, I’m a resident physician, and used to be an engineer. I built one of these boxes from a 75 watt pond clarifier to disinfect my wallet, keys, stethoscope, etc when I get home from work. The design is pretty much the same, except that I used spray glue and aluminum foil. I used a UVC dosimeter probe and get ~9 mW/cm2 at the bottom of the tub, so 1 J/cm2 would be reached in about 2 min. Each bulb is going to be different though. I get ~5 mW/cm2 at the edges. Remember that irradiance drops off inversely of distance squared.
Disposable air purifying face masks are generally considered single use because the seal is unlikely to be adequate with re-use. Sterilising each side of the filter medium does not address the issue of the adequacy of seal achieved with re-seating on re-use.
Thanks, doc – nice to see an informed opinion and some sources to back it up.
Stay safe out there.
I like your build.
It’s clever and accessible.
Keep up the good work.
I’ve been interested in this since very long and thought UV-C producing LED would be the most effective and reliable option, but they are extremely expensive, I just hope that this pandemic will make them mass-produced, so they get as cheap as other LED…
265nm leds on eBay. I got 30 of them for 62 bucks.
There’s a lot of dangerous misinformation like this article. It doesn’t mention what wavelength the UVC light is. Anything higher than 222nm is dangerous to the skin and eyes.
Stanford University’s N95 sterilization methods with warnings:
Of course the simpler method is burying that mask in SALT.
Remarkable what salt does. Within four hour’s it’ll kill cronovirus and a host of other 99% nasties.
Spend $50 or get a bucket of salt.
Please be kind and respectful to help make the comments section excellent. (Comment Policy)