Gregory's Server@pezmico I've been unable to understand why people have been putting up mechanical filters and not sticking UV lamps into the HVAC ducts. Maybe it's because the filter industry is supporting future sales?
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@dean @libroraptor I also know little about it, but I remember them being part of the #DavosSafe protocols. I've read they're helpful although probably need a more strategic placement. I wonder about the effectiveness of this one lamp just standing in the corner of the room, but I guess it can't be worse than not having it. UV-C light is pretty high energy light, which breaks down molecules and thus kills off germs. But breaking down molecules also means it creates free radicals - highly reactive short-lifetime chemical compounds, that seek to react with other things they come into contact with. This might mean combining with one another in the air and creating entirely new chemicals that have very little with their original source chemicals. This might also mean damaging your tissue if you come into contact with them, most likely by inhaling. That smell of freshly baked bread and sweets has a lot of chemicals in it, disassembling those chemicals and re-assembling them in a random way is quite a chemical experiment. On the other hand, fine enough filters (think HEPA) can remove viruses, and a carbon filter after particle filter can also serve as reactant to safely react with reactive chemicals in air and remove free radicals and VOC.  Naomi Wu is a Cantonese Maker who has covered this extensively in a series of very thorough videos. How it works, how it is safely done and how to install, how to do it cheaply. You want a very specific kind of UV light source, 222 nm, https://twitter.com/realsexycyborg/status/1436691276921860099?lang=en, and install it in air ducts or filters to deactivate virus material,  @isotopp @pezmico @dean For the school contexts that I'm thinking about, home-made won't do – it'd have to be a commercially supplied one from the HVAC company. These things have been around for years; what I'm wondering is whether there is an important reason why they're not being promoted while filtration is. @libroraptor @isotopp @pezmico @dean @mmlvx @isotopp @pezmico @dean I didn't think to check Wikipedia before, but it turns out that they have a broad-and-thin, inconclusive, but at least reasonably current, summary https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation#Air_disinfection  I am not an expert, but the impression I get is that this is new technology using very specific kinds of UV light, called "Deep UV": @FediThing @dean @pezmico It's been in commercial production for years, and is available for home installation. It's used both for sterilising the air and for sterilising internal coils (microbe habitat surfaces). I don't know how well regulated it is, though, notably on the ozone concentration front. HVAC sizing is something that people often get wrong so it wouldn't surprise me if people often choose excessively powerful UV bulbs and end up with far more ozone than is healthy. @dean @pezmico UV-C is typical for sterilising HVAC air. What I'm thinking about here is situations with ducted air – we could sterilise the entire supply rather than trying to filter and recycle what's already inside the room, especially since we still need to remove stale air. How much energy the UV irradiator consumes depends on how big a bulb (or bulbs) the HVAC system needs.  @libroraptor @pezmico UV lamps also attract insects, which is why many restaurant kitchens have them in fly zappers. The wavelengths might differ slightly between the bug-attracting bulbs and the germicidal bulbs, but I can see UV in the ducts without also having a physical barrier being a real problem. https://www.bhg.com/home-improvement/porch/outdoor-rooms/best-bug-zappers/ @LinuxAndYarn @libroraptor This may be the actual reason they had an UV light. A lot of dead bugs were inside the shield. @pezmico @LinuxAndYarn My parents used to have a low-wavelength one for generating ozone when they had a motel. They used to to clean out units when people had sneakily smoked inside. The ozone would eat the tobacco stench out of the wallpaper and carpets. @pezmico @libroraptor Yeah, if it was one that sat on the wall in a big bowl-shaped sconce that was a bug zapper. |
@libroraptor @pezmico I didn't know UV lights would be effective. Unless it's designed extremely well and positioned correctly I feel like it would do very little. Do you know more?
But very cool the shop is still following protocol.