There are a lot of new products out there getting a lot of attention these days. Of these are the UVC wands and UVC boxes. I’ve been researching these specifically for a few months and have had the opportunity to test a few individual products.
Most product marketing illustrates that the device kills 99.9% of bacteria or viruses. This is likely factual, however it fails to mention how LONG it would take using the specific device to actually achieve that level of disinfection! I find this to be misleading marketing.
The International Ultra Violet Association has published that to kill SARS viruses one needs to irradiate with a dose of 20 mJ/cm2. There still hasn’t been enough testing on Covid-19 to determine (and publish) it’s killing doeage; however, experts think it will be similar to SARS and hence, until specific Covid testing has been done, numbers from SARS are being used. Note that different organizations have different measured kill dosages.
Boxes are one thing, very different from hand held wands. The box I tested emitted an intensity of approx. 0.049 mW/cm2. I use a dosimeter calibrated to the 254nm UVC wavelength to measure the intensity of such devices. The standard box run cycle is 3 minutes. I.e. push the button once and it automatically runs for 3 minutes before shutting off. This intensity at this duration (180 sec) generates a total of 8.8 20mJ/cm2. [0.049 mW/cm2 x 180 sec = 8.82 mJ/cm2] This illustrates that the 3 minute cycle doesn’t even deliver HALF the required dose. With these numbers one would need to run approx. 2-1/2 cycles. Not hard to do, but no one is advertising the actual time required to really KILL viruses!
Its different with handheld wands because someone is actually holding this device the entire time required for disinfection. As above, the killing dose is the product of the light intensity and the duration. First, I see many wands that market that it takes 20-30 seconds to disinfect up to 99.9%, similar to the boxes. However for the wands this represents an extremely small area that is illuminated by the wand while held about 1 inch above its surface. If the ‘waving’ motion is more than an inch or so in each direction, the light intensity reduces to an almost immeasurable level.
Marketing literature shows people ‘disinfecting’ hotel beds with a 10” wand. This would take hours! No one would ever do this effectively. Even if 30 seconds would kill Covid-19, this feels like a very long time to the person holding the wand, and remember, this is 30 seconds for each small area to be disinfected. A typical 13” laptop keyboard is approximately 5x the width of a phone and would therefore take 150 seconds, 2-1/2 minutes. This feels like an eternity!
Further, with the wands there are two types, bulb or LED. In my tests the bulb version emitted 10x the intensity of the LED wands. Interestingly, one of the LED wands I tested had 18 individual LEDs which look like tiny metallic squares on the underside of the wand. In my testing I identified that only a small amount of the LEDs were actually UVC wavelength and the others were UVA light with NO DISINFECTING QUALITIES. So, buyer beware! Be sure to check the product you’re buying. I’d recommend asking what light intensity should be expected and at what distance from specimen. You can then do your own math to calculate how long you need to kill Covid or other germs.
So, overall there is some good technology that can help keep us safe. That said, as with anything in my opinion, we need to be somewhat intelligent about what we buy and verify efficacy of products we rely on. At least with UVC boxes one can run multiple cycles to ensure disinfection. With wands, find a higher power device so you don’t have to spend all day going back and forth.