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Related question: is UV light useful or practical for household sanitizing? Specifically I'm thinking about dirty dishes in the kitchen. Say, a cutting board th

Related question: is UV light useful or practical for household sanitizing? Specifically I'm thinking about dirty dishes in the kitchen. Say, a cutting board that had raw chicken on it. Would UV light render such a surface safe? What about in, say, a dishwasher? Could sanitize cycles use less energy that way?

ClumsyPilot 6y ago
UV light can't get into cracks, penetrate dirt, nooks and crannies, so steam in the dishwasher will do a better job. It can create Ozone, which kills bacteria and damages respiratory tracks. It can be a bug or a feature in the right hands. Hard UV also leaves a nasty sunburn. In Russia it's used for domesric disinfection for a long time - you turn on a big lanp and leave the room for a few hours.
- liability 6y ago
  In the right context, the generation of ozone is a feature because ozone can penetrate into cracks and whatnot that are shadowed from the UV itself. I do wonder how much you'd need for this to be truly effective though.
- legerdemain 6y ago
  Oh god, homemade "ozonators" like this bare mercury lamp one.[1] HN sometimes has a misplaced admiration of ex-USSR-ian resourcefulness, but the cultural climate of top-secret alternative cures and conspirology is exactly what popularizes breathing cures, DIY bleach injection, "bringing the light inside," and other desperate, dangerous self-experimentation. A top result for "ozonator" in Russian advertises that ozone therapy is "used for wound-healing, immune system recovery, removal of cellulite, and obesity." Just breathe it in! [1] https://upload.wikimedia.org/wikipedia/ru/0/00/Ozonator.jpg https://upload.wikimedia.org/wikipedia/ru/0/00/Ozonator.jpg
  - ClumsyPilot 6y ago
    Dude, wth. I am talking about actual proper device that you place in a room, leave the room and it runs on a timer. That's what normal people have. Sure there is a fascination with alternative medicine in Russia, but thats a separate problem, among many others.
    - legerdemain 6y ago
      I don't know what kind of modern luxury you live in, but the hobo arc lamp version is what my family and friends of the family had, and it's the primary illustration on Russian Wikipedia.
      - ClumsyPilot 6y ago
        I mean it's still a mercury lamp, the same thing, just in a metal box and with a timer. I remember seeing it since age of 12, and noone was trying to make me breathe ozone. There were folks advising my parents to treat skin burns with urine of a young piglet, but fortunately no-one was taking them seriously.
dmurray 6y ago
There are products like this (Google for "UV sterilizer box"). Pretty sure they work fine. But they take a lot longer than wiping with soap and hot water or disinfectant. For dishwashers it's going to be difficult to make sure you expose every surface of every utensil, compared to filling the machine with hot air and steam. You'd need a much more space-hungry design than standard models.
GloriousKoji 6y ago
It's not practical because the amount of time required for the UV light to scramble everything would be too long or the power of the UV light required for a small amount of time would be too dangerous. It's also hard to ensure light gets into all the places it needs to get into, soap and water does a much better job.
gwittel 6y ago
As others said, typically the required exposure is too long. On top of that, many household items may not be UV safe and will degrade (some plastics), or discolor (plastics, fabrics, etc.). To top it off, you can end up just killing the less UV resistant bacteria, and selecting for the stronger ones. Oops. Proper UV sterilization takes time (minutes, hours). I'd worry that many people will just wave a light and think "its clean". It doesn't work that way.
Viliam1234 6y ago
First, UV light also casts a shadow. So if there is a small piece of dirt on the dish, viruses under that dirt are protected from the light. Two dishes on top of each other, the viruses on the lower one are protected. Also, the lower part of the dish, and the table under the dish. Ultimately, you could only use the UV light to sterilize an empty table, assuming you cleaned it up first. But yes, this is how UV light is sometimes actually used. Shining on an empty table in a lab, for one hour. Even then, you don't take it as a 100% guarantee that there are no viruses left. Second, UV light hurts humans, too. Ignore the safety and remain in the room when the UV light is turned on, you get cancer. In the lab, people are careful. In an average household, it would be a question of time before someone gets exposed to the UV light. If you are careful, you can use the UV light on your room, or kitchen, and it is "better than nothing". (Not sure if you even need to cover your windows, because I think glass already reduces the UV part of light, plus the intensity is reduced by square of distance so you probably wouldn't hurt random people on the street.) But it takes a lot of time, and it only reduces the number of viruses by some fraction. Considering that COVID-19 is usually spread by air, not by touching surfaces, opening your windows probably achieves much more than using the UV light in your room or kitchen. For some other viruses, the numbers could be different. Also, the dishwasher already kills a lot of viruses by using higher temperature than when you wash dishes by hand.

ClumsyPilot 6y ago

UV light can't get into cracks, penetrate dirt, nooks and crannies, so steam in the dishwasher will do a better job. It can create Ozone, which kills bacteria and damages respiratory tracks. It can be a bug or a feature in the right hands. Hard UV also leaves a nasty sunburn. In Russia it's used for domesric disinfection for a long time - you turn on a big lanp and leave the room for a few hours.

liability 6y ago
In the right context, the generation of ozone is a feature because ozone can penetrate into cracks and whatnot that are shadowed from the UV itself. I do wonder how much you'd need for this to be truly effective though.
legerdemain 6y ago
Oh god, homemade "ozonators" like this bare mercury lamp one.[1] HN sometimes has a misplaced admiration of ex-USSR-ian resourcefulness, but the cultural climate of top-secret alternative cures and conspirology is exactly what popularizes breathing cures, DIY bleach injection, "bringing the light inside," and other desperate, dangerous self-experimentation. A top result for "ozonator" in Russian advertises that ozone therapy is "used for wound-healing, immune system recovery, removal of cellulite, and obesity." Just breathe it in! [1] https://upload.wikimedia.org/wikipedia/ru/0/00/Ozonator.jpg https://upload.wikimedia.org/wikipedia/ru/0/00/Ozonator.jpg
- ClumsyPilot 6y ago
  Dude, wth. I am talking about actual proper device that you place in a room, leave the room and it runs on a timer. That's what normal people have. Sure there is a fascination with alternative medicine in Russia, but thats a separate problem, among many others.
  - legerdemain 6y ago
    I don't know what kind of modern luxury you live in, but the hobo arc lamp version is what my family and friends of the family had, and it's the primary illustration on Russian Wikipedia.
    - ClumsyPilot 6y ago
      I mean it's still a mercury lamp, the same thing, just in a metal box and with a timer. I remember seeing it since age of 12, and noone was trying to make me breathe ozone. There were folks advising my parents to treat skin burns with urine of a young piglet, but fortunately no-one was taking them seriously.

dmurray 6y ago

There are products like this (Google for "UV sterilizer box"). Pretty sure they work fine. But they take a lot longer than wiping with soap and hot water or disinfectant. For dishwashers it's going to be difficult to make sure you expose every surface of every utensil, compared to filling the machine with hot air and steam. You'd need a much more space-hungry design than standard models.

GloriousKoji 6y ago

It's not practical because the amount of time required for the UV light to scramble everything would be too long or the power of the UV light required for a small amount of time would be too dangerous. It's also hard to ensure light gets into all the places it needs to get into, soap and water does a much better job.

gwittel 6y ago

As others said, typically the required exposure is too long. On top of that, many household items may not be UV safe and will degrade (some plastics), or discolor (plastics, fabrics, etc.). To top it off, you can end up just killing the less UV resistant bacteria, and selecting for the stronger ones. Oops. Proper UV sterilization takes time (minutes, hours). I'd worry that many people will just wave a light and think "its clean". It doesn't work that way.

Viliam1234 6y ago

First, UV light also casts a shadow. So if there is a small piece of dirt on the dish, viruses under that dirt are protected from the light. Two dishes on top of each other, the viruses on the lower one are protected. Also, the lower part of the dish, and the table under the dish. Ultimately, you could only use the UV light to sterilize an empty table, assuming you cleaned it up first. But yes, this is how UV light is sometimes actually used. Shining on an empty table in a lab, for one hour. Even then, you don't take it as a 100% guarantee that there are no viruses left. Second, UV light hurts humans, too. Ignore the safety and remain in the room when the UV light is turned on, you get cancer. In the lab, people are careful. In an average household, it would be a question of time before someone gets exposed to the UV light. If you are careful, you can use the UV light on your room, or kitchen, and it is "better than nothing". (Not sure if you even need to cover your windows, because I think glass already reduces the UV part of light, plus the intensity is reduced by square of distance so you probably wouldn't hurt random people on the street.) But it takes a lot of time, and it only reduces the number of viruses by some fraction. Considering that COVID-19 is usually spread by air, not by touching surfaces, opening your windows probably achieves much more than using the UV light in your room or kitchen. For some other viruses, the numbers could be different. Also, the dishwasher already kills a lot of viruses by using higher temperature than when you wash dishes by hand.