From bigclivedotcom.

These UVC germicidal lights will hurt you. If you expose your skin or eyes to 254nm UVC it will cause temporary damage, which can result in waking up in the middle of the night feeling like you’ve got sand in your eyes. It does pass though. It’s very similar to what welders experience when they get incidental eye exposure to a welding arc nearby.

The science suggest that while UVC may cause temporary irritation, it poses less long term risk that the longer UVB and UVA wavelengths that penetrate deeper into the skin and can potentially cause localised DNA damage.

This light is intended for aquariums. Not the bit with the fish in it, as it can harm them with direct exposure, but the separate area of the tank (or external area) that has the filtering in it. The purpose of the light is to destroy waterborne nasties that could adversely affect the health of the fish.

It has many other uses though, and could be used for keeping a tank of low throughput sitting water sterile. Like a rainwater tank. But for higher flow applications like a well water supply, a stronger unit is needed, which usually passes the flowing water across the surface of a longer UVC tube.

The lamp could potentially be used for air sanitation and limited area bacterial, viral and mite control.

The power supply is the simplest option possible for these common GTL3 bulbs. It’s just basically a series capacitor that limits the AC current to the correct level. It’s a common approach.

The bulb itself is very novel. It operates at about 10.5V AC at around 300mA and has a filament in it with a thermally emissive coating at the ends. Initially the filament heats up red hot and when the emissive coating is hot enough it establishes a glow discharge through the mercury vapour and carrier gas. Some current still flows through the heating filament though.

UVC output power is around 0.16W (160mW) which is still a lot. The quoted lifespan of 10,000 hours is too generous. While the bulb may still be lighting up at 10,000 hours it will be much less effective. These bulbs are normally rated for 2000 hours of UVC output before needing replaced.
I’m not sure if the use of a capacitive current limiter is good for them, as it can cause electrode sputtering in other similar applications.
These bulbs have a very long history way back to the thermionic valve/tube era.

The pandemic caused a new demand for these bulbs, and as usual, greedy people price gouged them. They are not expensive. This whole unit came from AliExpress and cost just $5 plus tax.
https://www.aliexpress.com/item/1005007286558169.html
I recommend using PayPal as a security layer when buying from AliX, as that way you don’t send your card details to them.

There are many sellers of these competing with each other, and also higher power units that don’t cost much more. I like the known simplicity of the 3W unit though.

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