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[Ninjabread]

GC, you really need read things more carefully, you've misread a little bit of info here, and then proceeded to base an entire argument off of the misread info.

Nitrogen has a greater mass than ozone, oxygen, C02 and the rest

Density of a gas is proportional to molecular number, so 32 for O2, 28 for N2 and 44 for CO2. Solubility is also a non-issue for gaseous mixing. CO2 is the most dense, but the densities are close enough that you still get thorough mixing.

Read carefully, and you'll see that nitrogen is the lightest gas that has been mentioned, not the densest.

I thought Bumber informed me that actually C02 was the same mass as oxygen

CO2 and O2 have similar densities

Similar, not the same. CO² is just O² plus 1 carbon atom, thus they have a similar, but not the same, density.

I am seldom wrong

Whether that's true or not, this is one of those times that you are wrong, GC.

[Grand Sage]

Alright, I've tried to read back a bit, but i cant find it: can someone recap how this in any way relates to dwarves smoking?

[therahedwig]

Something something, smoke needs to go somewhere. GC is trying to make smoke needing to go somewhere into an environmental factor that fundamentally changes the socio-cultural practice of smoking for dwarves. Meanwhile, forges, kilns, kitchens, stills, tanneries are ignored. For some reason, dwarves going outside to smoke while bitching about the weather is not an option, despite humans in the real world having this exact same practice.

[scourge728]

there's also the option of just not having the dwarves smoke, which it seems I'm the only person supporting

[Bumber]

Excuse me, what?!

Nitrogen has a greater mass than ozone, oxygen, C02 and the rest.  This is why close to the surface, nitrogen predominates and the air we breathe is hence mostly nitrogen; it sinks to the bottom of the atmosphere, which is where we are.

I'm sorry GC, but you need to actually do some research before spouting blatant falsehoods:

Gas	| Formula	| Molecular Weight	| Density
Nitrogen	| N2	| 28.02	| 1.165
Air	|	| 29	| 1.205
Oxygen	| O2	| 32	| 1.331
Carbon dioxide	| CO2	| 44.01	| 1.8421

We see N2 is the lightest and CO2 is the heaviest; though obviously not problematically so (since we can breathe.)
(There's also the fact that most of the atmospheric CO2 dissolves into the ocean so it can kill coral reefs, like good CO2 should, but that doesn't help our room.)

I started on the assumption that C02 was heavier than Oxygen, I thought Bumber informed me that actually C02 was the same mass as oxygen and I believed Bumber (did Bumber actually say density?)

I said, "Greater or equal." In other words, you can't rely on density to actively separate. You had it right here:

Did you know that CO2 is of greater or equal density compared to O2?

The relative density of C02 against O2 is largely irrelevant here.  That is because they are both gasses and gasses are prone to equalise themselves, this is a far more powerful force than their relative density is.  That means O2 will come from the surface and C02 will leave through the chimney, the relative density is not a problem.

Then we went on about if adding a second shaft was sufficient to offset CO2 conversion, and if a greater difference diffused faster. I reiterated that we knew they were "similarly dense" when countering the "faster diffusion" point.

I never brought up Nitrogen, so you really should have checked the density of that before claiming anything.

[UristMcVampire]

Or maybe just DON'T simulate the actual smoke, or use the vanilla smoke physics?

[thompson]

GC, would you please cite where you get your information from?

[GoblinCookie]

GC, you really need read things more carefully, you've misread a little bit of info here, and then proceeded to base an entire argument off of the misread info.

It wasn't much relevant to my general argument, which is why I let it pass.  My general argument was that diffusion happens between and within substances into which the gasses are dissolved, which is why you can breathe in a cavern even if it has no non-submerged entrance to the surface.  The oxygen dissolved into the water diffuses between the water and the nitrogen in the air, the C02 in the cavern air also dissolves into the water at the same time.

It seems now however that oxygen and C02 are suspended in the nitrogen rather than dissolved.  They will still diffuse within the nitrogen however, because this runs in parallel to the tendency of heavier gasses to sink it would seem that a more horizontal ventilation shaft would actually work better than a vertical one. 

I'm sorry GC, but you need to actually do some research before spouting blatant falsehoods:

Gas	| Formula	| Molecular Weight	| Density
Nitrogen	| N2	| 28.02	| 1.165
Air	|	| 29	| 1.205
Oxygen	| O2	| 32	| 1.331
Carbon dioxide	| CO2	| 44.01	| 1.8421

We see N2 is the lightest and CO2 is the heaviest; though obviously not problematically so (since we can breathe.)
(There's also the fact that most of the atmospheric CO2 dissolves into the ocean so it can kill coral reefs, like good CO2 should, but that doesn't help our room.)

You don't seem to have considered that I know that the weight of a substance is not just it's molecular mass.  It is also it's overall density, if you heat air up it rises above the colder air but this is not because the molecules have got any heavier. 

There isn't much C02 in the atmosphere compared to everything else, mostly nitrogen.  If the larger body of air goes in a certain direction, it carries with it the individual molecules that are part of it.  That means that if we heat up the air so it goes out of the chimney, it will carry the CO2 with it; if the flow of air is strong enough.  What do we have to worry about it what happens if the air cools down before leaving the chimney, then the C02 will sink freely and we are stuck with the stuff, which one more reason to prohibit individual smokers; we want a strong flow of smoke out of the fortress and not a lot of small puffs of smoke floating aroud. 

Or it might be that the difference in weight between the C02 and the nitrogen is too small to cancel out the diffusion in the opposite direction.  The C02 will always leave, but it just might not leave fast enough to counteract the speed at which we are making more of it. 

Then we went on about if adding a second shaft was sufficient to offset CO2 conversion, and if a greater difference diffused faster. I reiterated that we knew they were "similarly dense" when countering the "faster diffusion" point.

I never brought up Nitrogen, so you really should have checked the density of that before claiming anything.

I said nitrogen is heavier than oxygen and CO2 because when I googled it, it said it was so; if this is not due to it's greater molecular weight then it must be due to it's density; google seems to be wrong and so I am wrong also; Google also told me that the weight of oxygen does not matter much because it dissolved into nitrogen.  That makes sense also, because less dense substances dissolve into denser substances, if nitrogen is much heavier than oxygen but does not have greater molecular mass that means it has to be denser and the lighter it's molecules are the denser it is going to have to be to be heavier than oxygen. 

Google is wrong!   

GC, would you please cite where you get your information from?

Google and other people on the thread.  I admit I am very much out of my intellectual depth here but I have learned not to trust google; a useful life lesson I am sure.  If you intend to seldom be wrong, believing what google says is not the way to go about it.

[Bumber]

There isn't much C02 in the atmosphere compared to everything else, mostly nitrogen.

Our room is not equivalent to the atmospheric average.

If the larger body of air goes in a certain direction, it carries with it the individual molecules that are part of it.  That means that if we heat up the air so it goes out of the chimney, it will carry the CO2 with it; if the flow of air is strong enough.

It will also carry out oxygen just as easily. If the rate of oxygen entering the room is not greater than the sum of the oxygen consumed plus the CO2 created, the room is going to end up with a lethal gas composition, regardless of the amount being pushed out. (As cited earlier: <10% O2 lethal; >10% CO2 also lethal. Only 21% of the air coming in is O2 to begin with.)

That's not even getting into the issue of soot, which comes in solid clumps significantly more dense than air, and will not be leaving so easily. We can only hope the dwarven anatomy has a way of filtering particulate matter out of the lungs.

What do we have to worry about it what happens if the air cools down before leaving the chimney, then the C02 will sink freely and we are stuck with the stuff, which one more reason to prohibit individual smokers; we want a strong flow of smoke out of the fortress and not a lot of small puffs of smoke floating aroud.

Some of it will expand outwards to fill the room, regardless of temperature. Especially so since the fire tends to also heat the gases in the surrounding air.

If we're talking about individual dwarves smoking in the entire fortress, then there's more air volume for the CO2 to diffuse into, and potentially access to more vents. That's better than all your dwarves taking turns in the same room. Concentrating it all into one place is kind of bad, unless your ventilation is equipped to handle it. Just don't smoke near the booze stockpile or poorly ventilated areas.

[UristMcVampire]

Just use the vanilla smoke physics -_-

[GoblinCookie]

Just use the vanilla smoke physics -_-

That is what we are doing.  But what are those physics?

Our room is not equivalent to the atmospheric average.

The air in the room is still mostly nitrogen.  That is the important detail, the oxygen and C02 act rather as silt does in a stream, it will be carried along with the flow of air provided it is strong enough.  There is a circulation of air caused by the hot air rising through the chimney and the diffusion of air into the fortress through the ventilation shaft(s). 

It will also carry out oxygen just as easily. If the rate of oxygen entering the room is not greater than the sum of the oxygen consumed plus the CO2 created, the room is going to end up with a lethal gas composition, regardless of the amount being pushed out. (As cited earlier: <10% O2 lethal; >10% CO2 also lethal. Only 21% of the air coming in is O2 to begin with.)

That's not even getting into the issue of soot, which comes in solid clumps significantly more dense than air, and will not be leaving so easily. We can only hope the dwarven anatomy has a way of filtering particulate matter out of the lungs.

As the air goes up the chimney, air goes into the room as well.  That air has the general composition of the air on the surface since that is where it comes from.  The greater the flow of air out of the room, the greater the flow of air into the room.  By reducing the density of the air in the room, you draw more air in, increasing the ventilation. 

Some of it will expand outwards to fill the room, regardless of temperature. Especially so since the fire tends to also heat the gases in the surrounding air.

If we're talking about individual dwarves smoking in the entire fortress, then there's more air volume for the CO2 to diffuse into, and potentially access to more vents. That's better than all your dwarves taking turns in the same room. Concentrating it all into one place is kind of bad, unless your ventilation is equipped to handle it. Just don't smoke near the booze stockpile or poorly ventilated areas.

Yes the hotter the fire is, the faster the air from the fire will go up the chimney.  As air is removed in one direction, colder air is also drawn in from the surface through any available ventilation shafts; remember that colder, denser air sinks as well as hotter air rising.

Now none of this applies to individual smokers.  Individual smokers make smoke too cold and in too small quantities to ever leave the fortress and to ever create any noticeable flow of air.  Their emissions are trapped in the fortress and accumulate over time in deadly quantities.  The greater density of their emissions to the stale, unmoving air of the fortress causes them to become trapped in the fortress. 

[Dorsidwarf]

I'm pretty sure that if diffusion simply worked by the total pressure and the partial pressures weren't involved we would all collapse and asphyxiate since the fact that oxygen is taken up and carbon dioxide is passed out is a fairly major part of aspiration. I may be mistaken in general terms there since there's a membrane involved though

[Bumber]

As the air goes up the chimney, air goes into the room as well.  That air has the general composition of the air on the surface since that is where it comes from.  The greater the flow of air out of the room, the greater the flow of air into the room.  By reducing the density of the air in the room, you draw more air in, increasing the ventilation.

Airborne soot in the room counts towards the density, however, and it's more dense than air. You need surface wind or fans to pull it out.

Now none of this applies to individual smokers.  Individual smokers make smoke too cold and in too small quantities to ever leave the fortress and to ever create any noticeable flow of air.  Their emissions are trapped in the fortress and accumulate over time in deadly quantities.  The greater density of their emissions to the stale, unmoving air of the fortress causes them to become trapped in the fortress.

If the air is stale and unmoving, they're already dead without the smoke.

[GoblinCookie]

I'm pretty sure that if diffusion simply worked by the total pressure and the partial pressures weren't involved we would all collapse and asphyxiate since the fact that oxygen is taken up and carbon dioxide is passed out is a fairly major part of aspiration. I may be mistaken in general terms there since there's a membrane involved though

The blood is mostly made of water.  Oxygen and carbon dioxide both dissolve in water and then the former is also dissolved into the insides of red blood cells (though some creature's don't have these).  The interesting part is that dissolved gasses still diffuse, so a surplus of carbon dioxide in the blood still diffuses into the air of the lungs.  I think nitrogen also dissolves in small quantities into the blood, which is why we have to pee; the yellow in the urine is actually a nitrogen compound. 

Airborne soot in the room counts towards the density, however, and it's more dense than air. You need surface wind or fans to pull it out.

The soot is like little silt particles being carried along by the flow of a river and not like salt in the ocean.  The air moves and it carries the soot with it, the density of the air is not affected by this, because they are actually separate objects; it is only when things are dissolved like salt is in the seawater that they act as the same object. 

The hotter the air is, the faster it moves and the faster it moves the more effectively it carries soot with it.  So a very large fire is like a fan, it propels the movement and flow of air, both towards itself and above itself.  That means there are very strong economies of scale to underground fires, the bigger they are the more they increase the flow of air and improve ventilation which helps both to feed themselves oxygen and dispose of the smoke. 

If the air is stale and unmoving, they're already dead without the smoke.

The diffusion of molecules within the air is not the movement of the air, gas molecules are always moving, even if the air is completely still.  So provided there was not so many dwarves or fires within our fortress that it overwhelms the diffusion of gasses into and out of the fortress then we don't need fans to actually move the air in order for them to breathe. 

But fires are very oxygen hungry and if their oxygen demand is not met they produce deadly carbon monoxide before they sputter out. 

[Bumber]

The hotter the air is, the faster it moves and the faster it moves the more effectively it carries soot with it.  So a very large fire is like a fan, it propels the movement and flow of air, both towards itself and above itself.  That means there are very strong economies of scale to underground fires, the bigger they are the more they increase the flow of air and improve ventilation which helps both to feed themselves oxygen and dispose of the smoke. 

Your economy of scale only works if the increased airflow outpaces smoke production. And considering smoke production is the whole point of the fire...

All I can say at this point is that you should start a fireplace and throw a whole bunch of leaves on it, and see how well it works out for you. That alone will probably cause smoke to start filling your house.