_peachthief

We started primarily with hand calculations on the intensity of light and then moved to optical simulations with the help of the team at Ansys. Once we were happy with the design we were lucky enough to have Sandia National Laboratories test a prototpye device for us against a surrogate virus (MS2) to prove the actual effectiveness against sterilizing viruses. In the test it sterilized 99.7% of the MS2 virus at the standard air flow rate for it. MS2 is generally accepted as more difficult to sterilize with UVC than coronavirus and Sars-Cov-2 in particular. We have a few more details here as well a request for the full report.

For touching a contaminated surface and then putting it close to your eye or such, the main protection is the face shield part of your device which makes it a bit harder to poke yourself. The CDC has generally said that it's primarily transmitted by exposure to respiratory droplets, so combined with adequate hand washing and such it should keep the risk a fair bit lower.

- Chris (Helpful - UVisor Team)

Thank you, all good points, in regards to the negative test, if I remember right they run this as part of the overall test setup to get the background levels. As we were completing this as an extension to another test they'd carried out I don't think they ran that for our setup.

To what degree the virus size is related to the dose is still not a fully understood topic, with there being quite a bit of variation across different viruses. The use of MS2 was primarily to allow us to estimate our effective UV dose, which we could then translate to equivalency for Sars-COV-2. An unfortunate chain way to do it, but what we had available last year when there was only a few labs with access to Sars-COV-2.

The full device uses two of the chambers that were tested by Sandia, giving a flow rate of 60 l/min which as you say is equivalent to moderate activity.

- Chris (Helpful - UVisor Team)

Yes that is the easiest way to think of it! Instead of capturing the virus particles, the virus (or other pathogen) is sterilized by breaking the RNA chains with UVC. This means that there isn't a high air pressure fan required as there is for mechanical filters, allowing it to be a lot smaller and quieter.

- Chris (Helpful - UVisor Team)

As it's always got air flow going past the face and pushing the air out the bottom the fogging is a lot lower than with a cloth mask and glasses. Depending on the humidity and weather there can be some fogging around the mouth area but we haven't seen it affect vision in any of our testing, so can be useful for those wearing glasses for sure.

- Chris (Helpful - UVisor Team)

Yes, we've chosen a lamp that produces a narrow spectrum at 254nm, which is above the 185nm UV light that ozone is normally produced by.

- Chris (Helpful - UVisor Team)