Sorry, but this is a completely reckless and irresponsible advice to give here. These Nichia LEDs have a radiant flux around 1000 mW! Specular reflections from glass, tiles, mirrors and metals will put your eyes in immediate danger. And since UV is predominantly invisible to the eye, the photopupillary reflex will not engage at all, and consequently the retina will get a lot of UV exposure. Permanent eye conditions, such as cataracts and macular degeneration is linked with excessive UV exposure. When it comes to your vision, please don't fuck around.
That power level is only dangerous if it's a tightly focused beam and you're staring straight at it, from a close distance.
I had concerns about using the Luminus SBM-120-UV at work, which can output 10W of flux. It's so powerful it can burn paper, held around 1cm away from it. The optical and laser safety engineer did some exposure calculations and said, it's within safe limits, as long as you're over 1.5m away. It did seem a bit counterintuitive, but it's inverse square law at play. Admittedly the LED I'm using has a longer peak wavelength of 395nm, which is safer, but as I say, that's more than made up for by the fact it's 10 times as powerful. At a distance of 1.5m, the amount of radiation I'm exposed to is tiny, less than that of sunlight on a bright summer's day.
Thinking about this again.
The UV torch probably has a narrower beam than the power LED I used, which could mean that a direct hit, from 2m, would expose you to more radiation. I still stand by my previous statement: as long as you're not looking directly at the beam, you'll be safe. The only reflection which will pose a hazard is a mirror, from a close distance. Don't worry about diffuse reflections, which scatter the light in many directions.
If in doubt wear sunglasses, but don't worry about it too much. To put it into perspective, you get 478mW/(nm m
2) at 325nm, increasing towards 1W/(nm m
2) at 400nmm, from bright sunlight. Averaging the two figures, gives roughly (1+0.478)/2*75 = 55W/m
2 of UV from 325nm to 400nm. If your torch beam spreads over an area of >13.5cm
2, the power per m
2, will be less than of bright sunlight. Don't panic if you get exposed to more than this. As long as it's a brief exposure and you're not staring at it, you'll be fine. The pupil being dilated is a non-issue. Your retina won't get hit by that much UV, because a lot of it is absorbed by the cornea. That doesn't mean it's safe to stare into the beam, as the cornea can be damaged.
https://en.wikipedia.org/wiki/Solar_irradiancehttps://en.wikipedia.org/wiki/Ultraviolet_index