[corysama]

I recall an article from a long time ago that basically said “astronauts report” the moon smells like spent gunpowder and outer space smell like… I think it was ozone.

What they were actually reporting was the smell of the airlocks after they returned from their excursions. The moon has no atmosphere, so it has been accumulating dust from billions of years of asteroid impacts that have never come in contact with oxygen. Many of the chemicals in the dust are oxidative and so when it is exposed to air for the first time it rapidly oxidizes just like gunpowder!

And I think the outer space report was from space walks, and the explanation was that the first time the airlock itself was exposed to hard vacuum, the surfaces of the airlock would have a reaction that left a scent of ozone.

[jordanb]

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.

[dotancohen]

And if the sample did auto-ignite, what was the procedure?

[jordanb]

I read it in Buzz Aldrin's book. He mentioned getting rid of all the samples if that happened. I would think the bigger problem would be moon dust all over their suits, but he didn't describe a plan for that.

He said they thought the odds of that happening were remote though, so I guess they decided to risk it with the suits. Apparently he mentioned the problem to his dad who accidentally told a reporter sitting next to him on a flight leading to a big media cycle about "flaming moon dust" prior to the mission.

[bell-cot]

Throw all their samples back outside, then very carefully sweep the inside of the LEM and throw the broom & dustpan out too?

In theory, they could have been equipped to partially pressurize the cabin with (say) helium - which would allow some sort of vacuum cleaner to work. But that could have added a fair bit of mass (by the LEM's very tight mass budget standards).

[mapt]

This sort of scenario, which was thought too improbable to plan for, even by an organization as psychotically obsessed with astronaut safety as NASA, is exactly why human spaceflight was important for exploration. Because astronauts could improvise a sensible solution and the tech couldn't.

[jonas21]

If you didn't have the humans on board, you wouldn't need to pressurize the cabin with oxygen. Or even have a cabin.

[dotancohen]

Yes, the presence of humans adds additional challenges that we overcome and learn from. The learning is the entire point of these missions.

[verisimi]

Empty out a glass of water and blow the floating blobs towards the fire.

[quotemstr]

The moon has gravity. The blobs wouldn't float.

[TeMPOraL]

But you could pour water at the fire from across the room!

Lower gravity is giving the defender an advantage over the elements... at least until it gets low enough for things to start floating, when this flips around. In microgravity, water turns into floating blobs, but fire turns into actual floating fireballs.

Water blobs vs. fireballs. Pretty sure there's a nice videogame idea hiding in there somewhere.

[diegoperini]

> Water blobs vs. fireballs. Pretty sure there's a nice videogame idea hiding in there somewhere.

I like the way you think. :)

[Chaosvex]

Pretty sure it was a joke.

[monster_truck]

Nobody would joke about something as serious as moon fires dude, c'mon

[cineticdaffodil]

Improvise. Adapt. Overcome or perish. One of the first man in orbit almost died because his suit couldnt fold its arms in vacuum. The enterprise moment where you encounter something new and unforseen must be scary as fuck.

[nandomrumber]

Oxygen if the third most abundant element in the universe.[1]

The Moon minerals contain plenty of it:

The finer regolith, the lunar soil of silicon dioxide glass.[2]

Minerals forming the lunar crust are made up of oxygen, silicon, magnesium, iron, calcium, and aluminum, along with small amounts of titanium, uranium, thorium, potassium, and hydrogen.[3]

I figure you mean free oxygen or diatomic oxygen O₂, but that stuff is rare in the universe, as it’s quite reactive, and largely irrelevant for asteroid impact chemistry extreme heat and pressure, plenty of oxygen available in the rocks smashing together.

1. https://en.wikipedia.org/wiki/Oxygen

2. https://en.wikipedia.org/wiki/Moon

3. https://science.nasa.gov/moon/composition/

[semi-extrinsic]

Even though some minerals on the Moon contain oxygen, it doesn't mean the dust can't oxidize further when exposed to a gaseous atmosphere with high oxygen partial pressure.

[nandomrumber]

The dust is predominantly silicone dioxide (glass), which is notoriously stable / non-reactive.

[daveguy]

Exactly this. Oxygen in minerals is very different than gaseous oxygen.

[mapt]

But does the oxidative effect of rare short-lived impact atmospheres match the other chemistry associated with being exposed to billions of years of hard (blackbody) sunlight, solar wind, and cosmic rays on the surface of a body without much of a magnetosphere? How much are those impact oxides, particularly the ones in fine dust, shorn of their chemical bonds?

[helterskelter]

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).

[thescriptkiddie]

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_...

[sbierwagen]

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

[imzadi]

Challenger was destroyed on launch, not reentry.

[georgemcbay]

Yeah it was Columbia that was destroyed on reentry (17 years later).

[gwerbin]

Which incidentally is the shuttle that brought back LDEF.

[junon]

I always heard burnt steak.

[everyone]

They say that about vaccum. eg. an airlock after re-pressurising it after a spacewalk. Apparently a vaccum sucks stuff like sulphur from within steel to it's surface.

[junon]

Ah this makes way more sense.

[ItsClo688]

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

[adrian_b]

The danger is not really great.

Any dust on the Moon still consists mostly of silicates which cannot be oxidized.

When dust comes from meteorites, it contains a fraction made of iron sulfide (with small quantities of other sulfides) and another fraction made mainly of hydrocarbons.

The metallic sulfides can be oxidized, but they will not burn violently. The hydrocarbons are like a tar or pitch, because the volatile hydrocarbons would have sublimated in vacuum. So neither that tar is easily flammable.

The gunpowder smell is likely to be caused by the oxidation of the sulfides from the dust, which releases sulfur dioxide, the same like burnt gunpowder.

[stonecharioteer]

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?

[adrianN]

It took about a billion years of photosynthesis on earth before all the ferrous iron dissolved in the oceans was oxidized and atmospheric oxygen concentration began to take off.

[gus_massa]

... and it probably killed most of the then current bacteria/archea, because they were adapted to an atmosphere without oxygen https://en.wikipedia.org/wiki/Great_Oxidation_Event

[prox]

Fascinating

[ItsClo688]

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.

[dotancohen]

Isn't Mars red due to oxygenation of the rocks? Is that ancient oxygenation or is there some quantity of oxygen in Mars atmosphere today? Does the atmospheric CO2 sometimes break down (maybe under sunlight) and release some small quantity of O2 or might there be another source? Might something underground be respirating atmospheric CO2?

[rigonkulous]

The realistic read would then be, we'd be better off just blowing a giant bubble of water in any number of lagrange point and having ourselves a brand new water park to play with, bring dolphins to, etc ...

Oh wait no that's a different kind of read.

[cornholio]

Terraforming is an exceptionally energetic endeavor. Even if you had the perfect combination of icy asteroids with just the right amount of water, nitrogen, oxigen etc. and the means to hurl them towards Mars, this kinetic event would be so energetic that it would take centuries to millennia before the surface would cool to habitable temperatures. it's not physically possible to do it ex in the span of a human lifetime.

Ar the scale terraforming entails, the crust reactions with the new atmosphere are closer to a rounding error.

[lisper]

Just put a parachute on the asteroid.

;-)

[cornholio]

All that kinetic energy needs to go somewhere. It's irrelevant if the asteroid burns up in the atmosphere or if trillions of tiny parachutes heat the atmosphere.

I guess you could devise some scheme where kinetic energy is shed or transformed into useful tasks; for example, delivering to Venus an amount of water similar to Earth requires an icy ball half the diameter of the Moon - and the kinetic energy of this mass traveling at 10km/s is about half of the energy required to spin up Venus to a 24h cycle. So some space elevator like contraptions could hypothetically catch the snowballs and lay them on the surface while at the same time spinning up the planet.

But if you have the required clarketech it's unclear why bother with planets instead of creating exponentially larger and better habitats.

[lisper]

You must have missed the smiley emoticon. Yes, I am well aware that parachutes on asteroids won't work. It was a joke. (I used to work for NASA.)

[deepsun]

Well, oxygen _is_ poison. It's eager to react (sometimes violently) with almost everything. It rusts and oxidates perfect shiny metals and silicon making everything an oxide!

[lukan]

No. "Poison" refers to a substance toxic to humans, but we can be exposed to pure oxygen and breath it very fine. But yes, oxygen is dangerous.

[Symmetry]

"Poison" can also refer to a substance toxic to other animals. We say that chocolate is poisonous to dogs for instance. And a good fraction of Earth's biosphere was killed off by oxygen poisoning in the first of Earth's great mass extinctions.

Also, the dose makes the poison and excess oxygen actually can poison humans. Deep sea divers have to worry about excess oxygen inducing seizures if they mess up their breathing gasses enough. And even 100% oxygen at regular pressure will slowly damage the lungs, something ICUs have to worry about.

Nick Lane had a great book about oxygen, Oxygen, which maybe isn't as good as his book about mitochondria but is well worth reading.

[singularity2001]

if the moon will be settled it will be settled by AI embodied in some kind of (nano) robot or artificially created life.

[bell-cot]

Terraforming anything looks really expensive. Ask a finance guy to run numbers on terraforming places with gravity too weak to hold onto a useful atmosphere for any length of time*, and give you his opinion.

*say, Earth's moon

[jodrellblank]

There was a time (1930 - 1960) when Futurism believed we could do great things. Now I imagine a Moonbase or Mars base, and then it gets bought by Private Equity who cancel the maintenance budget, double the number of tourists, and when it OceanGate Titans with the loss of everyone, they shrug and the courts don't give them so much as a slap on the wrist.

That would never happen to the Starship Enterprise. Even in Total Recall, where the baddies wanted to kill the poor, they cared about the integrity of the base keeping everyone alive.

[bell-cot]

Maybe I'm not reading the right techno-utopian stuff - but I've never seen a Moon Base or Mars Base proposal which claimed to both have an actual business plan, and to project sustained profits.*

Having no prospect for sustained profits is pretty good for keep PE away.

(OceanGate Titan was a money-losing obsession project, not a viable business.)

*Except maybe the O'Neill Space Colony idea - where the Moon Base is just a Lunar strip mine, plus mass driver to throw the "ore" into orbit. IIR, they used a load of NASA's 1970's "lies we must tell Congress" numbers in calculating their transportation costs. And their whole scenario is about half a century out of date now.

[FranOntanaya]

Well, sort of. Solar wind does include oxygen ions, so it's exposed to a small extent.

[slow_typist]

How can it include oxygen?

[Groxx]

Stars kinda famously fuse elements up to iron as part of normal operations. And even if you exclude that, the entire solar system is leftovers from a previous star - all that is inside our current star too. Sure, much of it isn't at the surface, but there's not much of a reason to expect that literally zero of it randomly floats up among the lighter elements.

Have a reference tho: https://en.wikipedia.org/wiki/Solar_wind

[JumpCrisscross]

That said, "heavy ions and atomic nuclei of elements such as carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron" makes up only "trace amounts" of the solar-wind plasma [1].

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

[L_226]

> our current star

Looking forward to seeing the next one!

[ygra]

We first need to get rid of the current one in a few billion years. That won't end well for Earth, though.

[floam]

Stars make it, our sun is made of it, it’s the third most abundant element.

Distant third

[yubblegum]

Somehwat surprised to see there are twice more Oxygen atoms than Carbon.

[kortex]

Carbon + helium fusion is rather favorable, vs carbon production by the triple alpha process (3He), so it's just reaction kinetics essentially.

[Bender]

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.

[mr_toad]

‘Ozone’ is the smell of ionisation, ‘gunpowder’ the smell of oxidisation.

[IAmBroom]

Half right. Gunpowder is mostly the smell of sulfur compounds.

[coffeebeqn]

Photocopiers smell like ozone when they run if anyone’s forgotten the smell

[saltcured]

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.

[aduty]

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.

[Bender]

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.

[echelon]

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.

[KennyBlanken]

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.

[vintermann]

I don't trust most air purifier manufacturers. They totally would add a fancy-sounding feature which sounds good, even if it has negligible effect, or even negative effect. Case in point: they're still pushing ultrasonic humidifiers.

The tiniest particles aren't necessarily the most dangerous, so even if "clumping" worked as advertised, it wouldn't necessarily be good. Air filters are worst at filtering particles at about 0.3 microns, they're better at filtering smaller ones (I understand it has something to do with brownian motion). I wouldn't be at all surprised if a similar thing affected our biological "filters". Either way, if you have a filter, you don't need UV to clean air. Just push more air through it if you need cleaner air faster.

[dmurray]

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.

[JumpCrisscross]

> 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

[Brian_K_White]

Yes and it wasn't sarcastic, both things (what you said and what they said) are simply true. I think their point was not to be alarmist like you should stop breathing, but simply that everyone knows the one thing and most people don't know the other thing, and it gives scale or context to the "you don't want extra ozone".

[heavyset_go]

Part of aging is the result of oxidation of DNA over time and as cells reproduce.

[echelon]

The other posters here are right. I just wanted to point out the odd beauty in the fact that the fuel that makes our biology possible is also one of the things that is killing us. If you get a chance, read up a little bit on redox reactions and oxidative stress and take a moment to appreciate that.

We harness the energy of oxygen. It's the fuel that powers us. But it's also so reactive that it's constantly damaging our DNA and intracellular components. Over time it ages us, causes cancer (daily - our biology fights back!), and will ultimately be part of what wears us down and kills us.

Look at oxygen as a very reactive and energy abundant fuel. And then consider its abundance in our atmosphere. And then how it powers human locomotion, human biochemistry. And how it creates free radicals and chain reactions that strip our DNA and mutate base pairs. And all the tens of thousands - no, countless more - interactions and reactions it's having all throughout our bodies at all times. And how our biology evolved compensation measures to keep those deleterious effects at bay for as long as possible - as long as necessary - to enable reproduction.

Our biology is utterly awe-inspiring when you think about it. An incredible machine molded by our gravity well and abundantly available energy. Not just fighting against entropy, but actively sailing its turbulent energy gradients.

[Bender]

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/...

[alfiedotwtf]

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

[heavyset_go]

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.

[mjanx123]

How long would it take for the ozone to recombine back, if you didn't vent the house?

[rrr_oh_man]

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.

[genewitch]

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

[dreamcompiler]

> WARNING: Do not be in the room with any UV-C light for more than a few seconds.

This advice does not necessarily apply to far UVC (200-235 nm), which appears to be much safer for human skin and corneas than UVC outside this specific band. More research is needed before calling it "safe" but far UVC is almost certainly less hazardous than the rest of the UVC band.

Pay close attention to wavelength when purchasing UVC light sources.

https://en.wikipedia.org/wiki/Far-UVC

[bertylicious]

What about shadows? The UV-C light can't reach everywhere, right? What about the back and undersides of product packaging you want to sterilise?

[Bender]

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.

[rrr_oh_man]

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.

[LoganDark]

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.)

[colechristensen]

You might be smelling the oxidation of biologicals via ozone and UV might have the same chemical effect

[KennyBlanken]

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.

[Bender]

Don't worry I know what I am doing.

[VoidWarranty]

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.

[mjmas]

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]

[Bender]

Nothing strengthens an immune system like a weekly furry party or attending "tough mudders" events.

[manwe150]

That’s because the parent claim is known as the hygiene hypothesis and has been disproven by science, in common with anti vaccine claims. The immune system has not been shown to benefit from training, but has been shown to be damaged by illness.

[corysama]

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.

[adrian_b]

I assume that they talk about black powder.

The dust that comes from meteorites contains up to 4 fractions: silicates, which cannot be oxidized, metallic iron, which oxidizes, but it does not form volatile substances that can be smelled, hydrocarbons in the form of a tar or pitch, which can burn but it cannot be ignited easily, and finally a fraction made of iron sulfide (troilite) with small quantities of other sulfides.

In contact with air, the sulfides will be oxidized, releasing sulfur dioxide. Burning black powder also releases sulfur dioxide, which is the main reason for its smell. Burning pure sulfur will produce the same smell.

[lifeisstillgood]

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 :-)

[Bender]

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.

[vl]

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!

[blub]

No, UV is unrelated to your issue.

First you need to figure out if it’s a surface infestation because of condensation or if it’s a constructive thermal bridge. The latter can be solved by raising the surface (wall, ceiling, etc) temperature through insulation or more inefficiently special heaters designed for this purpose.

In both cases, the contaminated material is removed down to the plaster or masonry. Wood, wallpaper and similar materials will likely be deeply contaminated and must be removed. For areas larger than 1 sq meter, it’s better to get a specialized contractor which will use HEPA vacuum cleaners, special bags, etc to ensure that the mould spores don’t spread in other rooms.

For small areas the agents of choice are bleach or hydrogen peroxide, both available in products for home use.

[blub]

Was it from flooding or how did it get there? How did you detect it?

[MisterTea]

> And I think the outer space report was from space walks, and the explanation was that the first time the airlock itself was exposed to hard vacuum, the surfaces of the airlock would have a reaction that left a scent of ozone.

I work with industrial vacuum machinery and the big slow down in a vacuum system is coaxing out water vapor which sticks to chamber and plumbing walls like glue. My guess is dissolved oxygen in the water vapor or the water vapor itself reacting with dust particles.

[emsign]

Outer space smells like burnt flesh is what I've heard. Space is full of toxic polycyclic aromatic hydrocarbons which are created in novae and are everywhere in outer space in small amounts. They're the same chemicals that generate when organic compounds and fossil fuels are burnt.

Makes me wonder even more why some people really want to go and live there.

[tarcon]

Has anyone tried to breath space? :)

[emsign]

Maybe you try it. :)

[raffael_de]

i'm wondering how do people even know what ozone smells like?

[Wololooo]

Ever been next to an electric arc discharging? The odour you can smell is Ozone.

[jiggawatts]

It's the smell of photocopiers or laser printers operating.

[gsich]

smell during thunderstorms

[yubiox]

I used to have a hot tub and it had an ozone generating device for killing bacteria. I loved the smell but people here are saying if you can smell it you are getting dangerous levels of it. :(