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There was some concern when Apollo 11 landed that when they repressurized the LEM with moon dust samples inside it would start a fire. I think they had a small test article that they blew a small stream of oxygen over to ensure it wouldn't auto-ignite.
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the detail that kills me is moon dust has never contacted oxygen in billions of years, so every time an astronaut came back inside they were essentially doing a chemistry experiment for the first time. the whole moon is just waiting to react with air
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This is what trips me up about terraforming. If we learn to create an atmosphere, are we going to instantly poison the oxygen we introduce?
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great questionprobably not poison it directly, but you'd lose a significant chunk to oxidation reactions before reaching any stable equilibrium. the surface is essentially a massive reactive sink. mars has a similar problem, the perchlorate in the soil would react badly with a lot of things we'd want to introduce. the optimistic read is that oxidation reactions release energy and eventually reach stability. the pessimistic read is the timescale is geological.
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At least some ISS astronauts describe smelling burnt metal after returning from EVA, if memory serves. (Others may smell ozone, I've just always remembered hearing burnt metal).
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the exterior of the ISS is constantly exposed to small mounts of atomic oxygen, which is an incredibly strong oxidizer. probably in addition to ozone there is a huge variety of organic and inorganic oxides that get tracked in through the airlock.

https://en.wikipedia.org/wiki/Materials_International_Space_...

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Fun trivia (well, perhaps not fun) in the second paragraph: "the Long Duration Exposure Facility (LDEF), which was retrieved in 1990 after spending 68 months in LEO"

Long exposure, 68 months, right. But it was only supposed to be in orbit for 11! Challenger being destroyed on reentry made a mess of things.

https://en.wikipedia.org/wiki/Long_Duration_Exposure_Facilit...

>It was placed in low Earth orbit by Space Shuttle Challenger in April 1984. [...] At LDEF's launch, retrieval was scheduled for March 19, 1985, eleven months after deployment.[4] Schedules slipped, postponing the retrieval mission first to 1986, then indefinitely due to the Challenger disaster. After 5.7 years its orbit had decayed to about 175 nautical miles (324 km) and it was likely to burn up on reentry in a little over a month.[6][9]: 15

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Challenger was destroyed on launch, not reentry.
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Yeah it was Columbia that was destroyed on reentry (17 years later).
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I always heard burnt steak.
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My UV sterilizing lights make my room smell like O3 Ozone and that smells nothing like spent gun-powder to me. The only other time I have smelled the same thing is when there has been mass lightening events in the sky. Were they talking about actual black powder or nitrocellulose? I've smelled black powder at the range when people bring out their antique rifles and that also does not smell like Ozone to me.
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‘Ozone’ is the smell of ionisation, ‘gunpowder’ the smell of oxidisation.
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Photocopiers smell like ozone when they run if anyone’s forgotten the smell
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I also associate ozone with some electric motors, I think because they have brushes that arc during operation. Older power tools I encountered in the 1980s often did this, and you could see the blue arc if you looked into the vents at the right angle.
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Brushless motors are popular now, but if you get the cheaper cordless tools they'll still have brushed motors. I have some Black & Decker 20V ones that do it. They tend to have less torque but I don't need Milwaukee or Makita tools just for diy around the house.
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Photocopiers smell like ozone when they run if anyone’s forgotten the smell

Those are similar but sweeter. If I sterilize a room with UV it has a very distinct smell like nothing else aside from lightening and stun guns. I would UV the bathroom right now but then I have to vent the entire house and its 34F outside right now.

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Side quest: Can you tell more about the UV sterilisation thing? Why do you do that? How often? Where? It seems like such a specific thing to do.
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I primarily use them in the bathroom to kill off mold and bacteria about once every 3 months. I open up the water heater closet, drawers, etc... then I fire one of them up. I've used them in other places but the more they are used the more I have to vent the house.
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Has anything prompted you to do this? Have you been doing this for a long time? Have you noticed any changes (yes, I assume?!). Sorry for pelting you with questions, but this is so... interesting and I'm tempted to give it a shot.
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Hi, i am not who you asked, but i feel like i've done enough research and have some warnings. UV-C light itself is antimicrobial, but only for surfaces that the light touches, and in the case of cloth it needs to penetrate a bit.

There are at least two types of UV-C light bulbs, as well as literal ozone generators that use ceramic platen and a fan. The type of UV-C bulb that is most common on Amazon and Ali is ~254 nanometers, and _does not_ produce Ozone. It does leave a smell, but it's more like an oldschool hospital antiseptic smell. probably the smell of the dead germs, yay.

Now 185nm is actually the correct size to turn O2 around the bulb into O3 (and more oxygens too, i once read, i think, kinda like cracking hydrocarbons to make longer chains or something).

UV-C bulbs (not base, which is an edison base) that can sterilize a room in 5-15 minutes are about 15-20 CM tall, with four crystal tubes that are connected together standing up on the base. image here [0]

you must run a fan over them if you want your money's worth. they get hot, the bases get hot, it makes the most sense in non-carpeted rooms to aim the crystal down and the base up, so that is real rough on them. that took me 2 bulbs to figure out.

If you can find a reputable place to get the box with ceramic and a fan that lasts more than 5 minutes, let me know, because that's closer to what i want for bedrooms and stuff.

The UV-C 185nm bulbs work great to make a car stop stinking, too! completely removes cigarette smells, if the car hasn't been smoked in for a while. run the A/C full blast and run the bulb for 15 minutes, open the windows for 5 minutes, roll em, sniff. Still smell? another 10 minutes, in the back seat, full A/C blasting. vent, sniff. Faint smell? replace the cabin air filter. Charge customer(?)

and i'm going to respond to your followup question to the GP as well: Covid. Obviously. They were telling us it would live on groceries and deliveries and that, so i put all deliveries in my laundry room and dosed em with UV-C for a minute. CDC or whatever studies said that 10-60 seconds was more than enough to kill sars-ncov-2.

I only use it for freshening cars, rooms, bathrooms, etc now.

WARNING: Do not be in the room with any UV-C light for more than a few seconds. Do not look at the bulb for literally any more than necessary to ensure it is on and safe. they make safety goggles that wrap your entire eye sockets to protect from UV, too. if you get a 185nm bulb, either completely ventilate the room with fresh air, or leave it sealed for 60 minutes then open it up for a few minutes, all the ozone reacts and goes away or something.

UV-C hurts your skin, yes, but it will make your eyeballs literally itch. so don't, don't don't look at it. they are not blacklights.

[0] https://m.media-amazon.com/images/I/71LgjON7J+L._AC_.jpg

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I don't think any of you should want to be smelling Ozone.

Diatomic oxygen is already a highly reactive fuel that is killing us and giving us cancer every single day. The ozone species is even more oxidative.

Oxygen is how we move about the energy gradient, but it's also killing us. Ozone is worse.

"Air purifiers" with ionization are probably not worth the squeeze.

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Aside from "killing us and giving us cancer every single day", isn't "diatomic oxygen" the stuff we breathe every single minute and need to survive?

I'm not normally one to miss the sarcastic or satirical posts, but this one seems oddly earnest.

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> isn't "diatomic oxygen" the stuff we breathe every single minute and need to survive?

I think they're referring to oxidative stress [1] caused by cellular respiration.

[1] https://en.wikipedia.org/wiki/Oxidative_stress

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Part of aging is the result of oxidation of DNA over time and as cells reproduce.
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Absolutely. I vent the house after running UV lamps using a 4400 CFM air mover. I leave the house and run errands. I have 3 of these [1]

They have a remote control that "arms" them and it starts beeping slow, the faster, then much faster then activates. It kills insects be destroying their lungs and entirely destroys mold, bacteria and even damages viral material. Hospitals run the same lamps in wings that they close down for sanitation. The entire area has to be 100% vented.

[1] - https://www.amazon.com/AeraLight-Whole-Surface-UV-Sanitizer/...

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How does this affect surfaces like walls, finished wood furniture and floors, plastic, paint, etc?

I imagine it will cause some material to off-gas aldehydes at the very least.

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I worked for a germaphobe, and he put one of these ozone-injecting air purifiers in our tiny office. Every morning I would walk in and it felt like I was walking into a thunderstorm from the smell. No gunpowder, just thick ozone
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In general, if you can smell ozone, you should NOT be in that place.
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The permissible exposure limit for ozone is 0.1 PPM.

The IDLH (Immediately Dangerous to Life and Health) level for ozone is five ppm.

That's half of chlorine which is 10 ppm.

Most major brand air purifiers put out a very minimal amount; the ionization is beneficial because it makes the really tiny (and thus most hazardous) particles clump and fall/stick to surfaces faster.

It's the offbrand units that generate lots of ozone to make people think they're "doing something", and commercial ozone generators for car/room deodorizing, that you have to be extremely careful with. Those need to be set up and then the room left for hours for the ozone to react with stuff, and then ventilated thoroughly.

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Brushed DC motors (as in some drills, toothbrushes, etc.) emit ozone. Some light switches also create ozone-producing electrical arcing if you hold them perfectly between the on and off positions, or slowly cross the midpoint. (Less easy with the newer-style, less accessible rocker switches.)
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The only thing you're doing by sterilizing your house like that is making your immune system weaker.

Humans are built to withstand a constant assault on their immune systems. We couldn't have survived if we didn't.

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Don't worry I know what I am doing.
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Careful. The venn diagram bubble depicting your statement overlaps heavily with the anti-vaccine bubble.

Its a bit naieve to claim that cleaning one's home will result in an extinction of enough microbes so as to be threatening to our immune system.

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See: Polio

https://en.wikipedia.org/wiki/History_of_polio

> [...] Better hygiene meant that infants and young children had fewer opportunities to encounter and develop immunity to polio. Exposure to poliovirus was therefore delayed until late childhood or adult life, when it was more likely to take the paralytic form.[22]

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Nothing strengthens an immune system like a weekly furry party or attending "tough mudders" events.
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Thank you! I wish I could upvote this twice, fellow redditor!
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You might be smelling the oxidation of biologicals via ozone and UV might have the same chemical effect
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Sorry for the tangent, but you sterilise a whole room with UV light? Is that efficient ? Do you do it after tidying / cleaning ? Is there a medical reason for the extra part? Is it just cool :-)
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The house came with a bacteria that would normally be hard to get rid of. UV, bleach and peroxide took care of it. I just repeat the process to ensure there is no bacteria or mold. This seems to bother people in this thread which I find fascinating. A part of me wants to bring my black light to their dwelling.
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I have mold problem in one of the bathrooms. What would be your recommendation? Seal off bathroom and run UV, then vent? Or do I need to do entire house? I can also seal off bathroom and bedroom. Thanks!
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The ozone report was specifically about space walks. The gunpowder report was about moon walks.

Presumably, moonwalks would also have some ozone like the space walk did. But, maybe the burning-moon-dust gunpowder smell was a lot stronger than the vacuumed-metal/paint ozone smell.

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