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Comment by sgroppino | Hacker News Reader

I was thinking something like this https://www.ebay.co.uk/itm/283782783926 or even this https://www.amazon.co.uk/gp/product/B00J3EUJPA to build some kind of wand to sterilize packages or clothes as I walk through the door. Just checked your links - I'm surprised the output is super low: 48W only yields 120uW/cm2. Does it mean a 12W UVC lamp would yield ~30uW/cm2? In terms of virus sterilization, would I need to expose the surface to a 12W for 80sec to get the 2.4mWsec/cm2?

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ahh ok its not like a light sabre :)

its like a half life thing, the energy from the UV radiation makes the molecules of the virus shimmy and shake until it breaks, and this is time dependent so for a given |dosage| of UV you need wattage over time at distance from the source. it might be better to hang the garment in a closet or enclosure and expose it for a period of time.

in particular, the cuffs, and the upper chest lapel area, and the hip/pocket area these are typical hotspots.

just pictured myself with a Darth Vader mask and a UVC portable sabre to kill covid-19... re-reading those specs "Measurements were performed on a high-frequency, current limited electronic ballast and represent average values at 1 meter" - this means the output could be considerable higher at a few inches and it'll take only a few seconds to sterilize small garments (and mobile phones). It could work.

you just have to be carefull about repeated exposure of skin and eyes. light energy dissipates as a square function of distance the general idea is quarter the energy for 1 foot distance increase a quarter of that again when you get to 4 feet away...

maybe this is more concise:

https://en.wikipedia.org/wiki/Inverse-square_law

that sounds right the distance is the variable to get here its inverse square dependent. usually flux is at 1 foot distance to keep the measurements in a standard framework.

have a look here re inverse square:

https://en.wikipedia.org/wiki/Inverse-square_law

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