222 nm Far-UVC Use Case: At The Dentist

This is the first in a series of posts I plan to do on 222 nm far-UVC use cases, situations where that technology might be able to help protect us and some ideas on how to employ it.

I ran a very informal poll on Twitter not long ago, asking folks what situations were their biggest concern where they thought 222 nm far-UVC might be able to help. An important caveat is the focus in this instance is on consumer devices, rather than looking at commercial applications, which is a bit of a different animal. In other words, we’re talking here about tech you can bring to make a dental visit, for example, safer, rather than what the dentist might install at their office.

Note that a lot of what I’ll be covering is informed speculation, and a great deal depends on the particular equipment you have and the specifics of your particular situation. Further, I don’t talk about making things “safe” – there’s no such thing as a safe shared-air environment. We can reduce risk, often tremendously (and 222 nm far-UVC can really help), but nothing is 100% proof against infection in the scenarios we’ll be looking at, starting with the dentist. I don’t mean to be a wet blanket, but that’s the truth as I see it.

Also, remember that any time you can, you should always try to use additional protective layers in any given situation! Sometimes you don’t have many (or any) options, but if you can, add masking, filtration, ventilation, vaccination, and other protections (e.g., nasal sprays) to decrease risk.

Okay, with all of that out of the way, onward!

Dental Visits

Not surprisingly, this was the biggest concern that cropped up, for obvious reasons: you’re basically stuck in a chair, mouth agape, with one or more people poking around in your mouth, with their mouths and noses maybe 12 to 18 inches from yours. On top of that, there may also be times when you have to move between the chair and other equipment, say a specialized x-ray machine. Many dental clinics these days are also “open bay” designs, which don’t have structural walls between exam areas and aerosols can flow much more freely. And dentistry can kick up a LOT of aerosols, not just from folks exhaling, but from drilling, spraying water, etc.

While aerosols wafting around on air currents are certainly a threat, I submit the biggest threat is posed by the dentist and techs working on you, with their faces roughly (at a guess) 12 to 24 inches from yours. The typical ASTM-3 masks (the “baggy blues”) most dentists use will capture and divert some aerosols from hitting you in the face, but this is probably the worst near-field transmission problem you’re likely to encounter in a “professional” setting.

All in all, it’s a really great environment for SARS-CoV-2 and other airborne pathogens to spread.

How might you use 222 nm far-UVC help reduce risk in this environment, on top of other protections you may be using such as the Readimask hack, nitrous oxide, nasal sprays, or personal (or full-size HEPA)?

Oh, and remember: any and every time you can, put your mask (KN95 or better) on! Every breath you take through the mask reduces your overall risk.

Back to far-UVC: let’s divide the devices into general classes, which I’ll imaginatively call Low, Medium, and High Power based on input wattage (note: input Watts are a super crappy proxy for comparing devices, but we’ll roll with it for now).

Low Power (3-6 input Watt range)

Devices in this group would include things like the ErgoHealth X-One and the recently released Krypton MVP.

How would I use one of these? UP CLOSE AND PERSONAL.

I have two X-Ones that my wife and I use for certain things, the dentist being one of them. We hold them on our chest (if you have one, use one; if you have two, use both), as close as possible to the action without getting in the way, aimed roughly up over the nose to hit that volume of air between your mouth and nose and those of the dentist and/or techs working on you, to get the MAXIMUM amount of energy from the lamp into that air pocket, because the more energy you can concentrate there, the faster it’s going to kill virus.

Regarding exposure concerns, click here.

Remember: output from ALL far-UVC devices are governed by the inverse square law, which means the energy falls off FAST as distance increases. For example, let’s say you use the energy output at 1 foot as your benchmark. At 2 feet the energy will be *1/4* what it is at 1. At 3 feet it will be *1/9*, etc. So distance matters – a LOT.

Are these better than personal HEPAs like the QT3? I don’t know. I suspect the QT3 should provide pretty good risk reduction because it has a decent cross-section and probably won’t draw in much room air with the flow before it reaches your mouth/nose (I think that’s more of a risk with something like the Pure).

Could you use both far-UVC and a small HEPA? Sure – there’s no law of physics that says you can’t, although it might start to get cumbersome.

Are small devices “good” for this purpose? No, but in many cases these days our choices are limited to taking crappy situations and doing what we can to make them less crappy. Low power 222 nm devices can help, but aren’t an optimal solution.

Medium Power (10-20 input Watts)

Examples of devices in this class would include the MobileShield222, UVPro222, Beacon (if it ever ships), Krypton Shield/Guard, and the Gerani and ErgoHealth M1 at the upper end of the power range (click here for more examples of mid-range devices).

IMPORTANT CAVEATS: I’m writing another post to talk about irradiance, which is essentially the energy OUTPUT of these devices, because the input wattage is a horrible proxy to compare “power”among devices. For example, the Care222 module by Ushio, which is used in many devices, including the UVPro222, Beacon, and Krypton Shield/Guard, has two variants: the B1 and B2. The B2 has a diffuser to increase the angle of coverage, but in doing so saps roughly 80% of the output compared to the B1, and is only about 50% more powerful than an X-One!! There are also devices that cycle on/off at 30 second intervals, which you do NOT want.

With that lengthy list of caveats out of the way, I’d generally use the medium power devices the same way as an X-One or MVP: on your chest. I’d move them down a bit further, not so much to reduce exposure (which in most cases I don’t think is going to be an issue), but to make sure you have the folks working on you in the main beam. This is especially the case with Ushio-equipped devices with the Care222-B1 module (which is the one *without* the diffuser), whose beam width is 60 degrees. But if you have one with a diffuser, I’d move it as close as you can.

High Power (60 input Watts and up)

High power devices like the ErgoHealth M1 Pro (60 input Watts) and Sterilray Sabre (150 input Watts) have some different considerations.

First, you don’t want to plant one of these on your chest: you’re definitely likely to run into some exposure overload there!

Most dental exam rooms or bays I’ve been in were roughly 10-12 feet square, give or take. So see if you can use a shelf, one of those little portable tables, or a chair to put the device on along a wall or in the corner.

IMPORTANT: 222 nm far-UVC devices kill virus via line of sight ONLY – so any virus that’s in the shadow behind anyone or anything blocking the light isn’t getting killed. When positioning your high power device, you’ve got to make sure it has a clear view to that volume of air between your mouth/nose and those of the dentist and techs. Typically the best spot is going to be in the direction of your feet or off to one side a bit, and high enough to see right into that 24-36” diameter air pocket you’re all breathing into and from. MAKE SURE it’s in a good spot: if you can’t see the lamp if you raise your head a bit to look, it’s not killing the virus in front of your face.

Bigger devices like these, especially the Sabre, can be bulky and cumbersome to use. On the flip side, they can do a great job blasting not only the virus in front of your face, but zapping it from the general room air, as well. All things considered, using a high power device is going to give you the best risk reduction by a considerable margin (note that this applies to the vast majority of use cases, except in confined spaces like a railroad car or very small office).

I’ll be posting some more use cases as we go along…

222 nm Far-UVC Use Case: At The Dentist

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