Top/side ventilation from the view of molecular motion

woodermeloon

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I have a B.S in chemistry and a minor in physics. I spent a year studying thermodynamics and particle motion and I will tell you that from our modern understanding of particle motion top ventilation will let out just as much moisture as side ventilation.

Liquid water evaporates when enough energy is transferred into the water molecules to break the attractive forces the water exerts on itself. The newly freed water vapor is going to exert uniform pressure on all sides of the container and will be equally likely to escape through any side if all sides are the same size.

The only things that are going to effect tank humidity will be.... the number and size of the holes present, air movement against the container (dry air will essentially steal moisture from wet air), and the temperature at which the container is kept.

Do not think that punching only holes on the sides will give you superior ventilation than only poking holes on the top or vice-versa.
 
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EulersK

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Great info, thank you!

I do have a question, though. It's been a common myth on these forums that humid air rises, so top ventilation will lead to moisture immediately being lost. I've never bought this for two reasons. Firstly, energy has to be invested into liquid water for it to evaporate, meaning the resulting humid air is slightly cooler than surrounding air. Since cool air sinks, would it not just stay at the bottom of the enclosure? Further, humid air is also slightly heavier than dry air, once again leading it to settle at the bottom. These are both assuming that there is no turbulence present, I understand that, but is what I'm saying generally true? And if so, wouldn't air holes at the very bottom of the enclosure result in much more moisture lost than anywhere else?

I'd love to read more on this. My BS is in mathematics and my MS is going to be in industrial engineering - a physicist I am not, but I can understand the math. Do you have any suggested readings on this topic? If I can get the general formulas (maybe with some help from you!), I may be able to make a video simulation of an enclosure with various ventilation holes in Matlab.
 

woodermeloon

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Great info, thank you!

I do have a question, though. It's been a common myth on these forums that humid air rises, so top ventilation will lead to moisture immediately being lost. I've never bought this for two reasons. Firstly, energy has to be invested into liquid water for it to evaporate, meaning the resulting humid air is slightly cooler than surrounding air. Since cool air sinks, would it not just stay at the bottom of the enclosure? Further, humid air is also slightly heavier than dry air, once again leading it to settle at the bottom. These are both assuming that there is no turbulence present, I understand that, but is what I'm saying generally true? And if so, wouldn't air holes at the very bottom of the enclosure result in much more moisture lost than anywhere else?

I'd love to read more on this. My BS is in mathematics and my MS is going to be in industrial engineering - a physicist I am not, but I can understand the math. Do you have any suggested readings on this topic? If I can get the general formulas (maybe with some help from you!), I may be able to make a video simulation of an enclosure with various ventilation holes in Matlab.

Molecules do not travel in a linear fashion their motion is random and sporadic. In the above simulation you see molecules escaping not only from the top but also from the sides. Also gas molecules are assumed to not be affected by gravity because their mass is so small and the energy needes to free them is so great in comparison.

I will find my physical chemistry book today and will give you a few equations which dictate particle motion. Mimicking this behavior in matlab is the kinda stuff people normally get grants to do lol.
 

EulersK

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Molecules do not travel in a linear fashion their motion is random and sporadic. In the above simulation you see molecules escaping not only from the top but also from the sides. Also gas molecules are assumed to not be affected by gravity because their mass is so small and the energy needes to free them is so great in comparison.

I will find my physical chemistry book today and will give you a few equations which dictate particle motion. Mimicking this behavior in matlab is the kinda stuff people normally get grants to do lol.
Ah, got it, thank you. Well that actually relieves a bit of stress. Several of my enclosures only have ventilation on one side, and I've worried about the implications of that.

But understand I won't be dealing with millions or even thousands of molecules. It would be a matter of a few hundred and perhaps just over a thousand (I doubt my computer could handle much more)... not to mention, I have access to a library of premade Matlab programs that I'd be able to just tweak ;) Like I said, maybe. There is a program that looks promising, but it's doing the demonstration with helium. Not sure if I'd be able to fix that, I'd need to look at the code.
 

Bugmom

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I put holes in the side, and frequently none on the lid, simply because I stack enclosures. I tend to go for more ventilation vs less because I never run fans in the room that the inverts are in (and we have no A/C), so there's very little air movement across the enclosures. The heater will cause some air movement, but obviously that's not a year-round occurrence.

The only things that are going to effect tank humidity will be.... the number and size of the holes present, air movement against the container (dry air will essentially steal moisture from wet air), and the temperature at which the container is kept.

Do not think that punching only holes on the sides will give you superior ventilation than only poking holes on the top.
I live in a high-humidity area. How does that factor into this?
 

Venom1080

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isnt the idea of cross ventilation to not allow as much moisture to escape as hole in the top?
 

EulersK

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isnt the idea of cross ventilation to not allow as much moisture to escape as hole in the top?
That's his point - holes in the side will allow just as much moisture to escape as holes in the top. Which is great news for us.
 

EulersK

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whys that good news?
It means that we don't have to obsess over ventilation of any kind, so long as there's enough ventilation. Location doesn't matter since the water molecules are uniformly distributed.
 

woodermeloon

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Eulers is correct, what I'm saying is a hole is hole wether it is put on the top or side of the enclosure. This is especially true since most are tarantulas are kept in places with little ambient air movement.

I live in a high-humidity area. How does that factor into this?
Humidity is the amount of water molecules present in gaseous air. At 100% humidity air cannot hold anymore water (it's around 100% humidity when it's raining), at zero percent humidity there is no water present in the air. Very generally, if you live in a place where the air is already humid, the air will not be able to pick up as many water molecules as "dry" air would be able to. Overall if you live in a humid area it is going to take longer for your tank to dry out. If you live the desert you will be filling up the dishes quiet frequently.
 

viper69

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It means that we don't have to obsess over ventilation of any kind, so long as there's enough ventilation. Location doesn't matter since the water molecules are uniformly distributed.
I think the typical differences between USA keepers, esp for Avics, (side ventilation) vs EU keepers (low front facing with strip of top vent) already supports this.

I've been thinking and saying it more on the forum lately w/Avics at least, that it's not the position of vent per se, but that they receive the proper amount of air exchange for their survival.
 

Bugmom

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Eulers is correct, what I'm saying is a hole is hole wether it is put on the top or side of the enclosure. This is especially true since most are tarantulas are kept in places with little ambient air movement.

Humidity is the amount of water molecules present in gaseous air. At 100% humidity air cannot hold anymore water (it's around 100% humidity when it's raining), at zero percent humidity there is no water present in the air. Very generally, if you live in a place where the air is already humid, the air will not be able to pick up as many water molecules as "dry" air would be able to. Overall if you live in a humid area it is going to take longer for your tank to dry out. If you live the desert you will be filling up the dishes quiet frequently.
I've lived in both a very, very dry area (New Mexico) and now live in a humid area (western Washington). So I'm familiar with fighting the dry air of the desert. But I've been battling mold in enclosures since I moved up here, and so I'm curious if I don't have enough ventilation. I feel like I do - I don't skimp on airholes. Yet the mold persists.
 

EulersK

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I've lived in both a very, very dry area (New Mexico) and now live in a humid area (western Washington). So I'm familiar with fighting the dry air of the desert. But I've been battling mold in enclosures since I moved up here, and so I'm curious if I don't have enough ventilation. I feel like I do - I don't skimp on airholes. Yet the mold persists.
I fight with mold as well. Try mixing in peat moss into your substrate, I've found that helps a lot. Or just use straight peat moss, that works too. I just think it looks terrible, so I mix.
 

woodermeloon

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I've lived in both a very, very dry area (New Mexico) and now live in a humid area (western Washington). So I'm familiar with fighting the dry air of the desert. But I've been battling mold in enclosures since I moved up here, and so I'm curious if I don't have enough ventilation. I feel like I do - I don't skimp on airholes. Yet the mold persists.
If it's 60% humidity in your home, your not going to get your encloser humidity below 60% without a dehumidifier.

I keep most my Ts on a 50/50 mix of peat and top soil i also add springtails and isos into all their enclosures. I havnt seen mold in awhile.
 

Bugmom

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I've used peat moss in the past, but found that it refused to absorb water. When adding any water to the enclosure, it would just bead up on the surface. How do you counteract that?

I don't have any problems with mold if I stick with coco fiber, but I've tried various organic soils and they all molded. Even the bag of organic soil I had just sitting in my garage molded. :mad: I feel like soil is a better choice for my burrowers, but not if it molds. I just rehoused my AF genic because her enclosure was full of mold even with a healthy isopod and soil mite colony in her tank (it started out as springtails and orange isopods but the soil mites in the soil out competed the springtails, I guess, cause not a spring in sight now).
 

EulersK

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I've used peat moss in the past, but found that it refused to absorb water. When adding any water to the enclosure, it would just bead up on the surface. How do you counteract that?
I haven't had that problem at all. In fact, peat moss is the only thing I can use that holds on to moisture for long periods of time. Are you sure you're using peat moss? The proper term is sphagnum moss - does other say that on the bag?
 

viper69

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If it's 60% humidity in your home, your not going to get your encloser humidity below 60% without a dehumidifier.

I keep most my Ts on a 50/50 mix of peat and top soil i also add springtails and isos into all their enclosures. I havnt seen mold in awhile.
How often do you have to add those cultures, how large is the setup?
 

Venom1080

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I've used peat moss in the past, but found that it refused to absorb water. When adding any water to the enclosure, it would just bead up on the surface. How do you counteract that?

I don't have any problems with mold if I stick with coco fiber, but I've tried various organic soils and they all molded. Even the bag of organic soil I had just sitting in my garage molded. :mad: I feel like soil is a better choice for my burrowers, but not if it molds. I just rehoused my AF genic because her enclosure was full of mold even with a healthy isopod and soil mite colony in her tank (it started out as springtails and orange isopods but the soil mites in the soil out competed the springtails, I guess, cause not a spring in sight now).
make sure the room itself is ventilated, not just the cage.
 

woodermeloon

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How often do you have to add those cultures, how large is the setup?
It depends on the species and the set up. I have an H.mac who is kept in a ten gallon on about 10" of top soil, peat, and sand. Her tank is also heavily planted. I added powder blue isos (p prainosus), giant canyon isos, and tropical springtails over a year ago and you can still turn over oak leaves in the tank and find them scurrying around.

In some of my small tanks which dry out more frequently, I will see food bulbouses and poop start to accumulate so ill go over to my spring colony, take a big oak leaf from the colony, and flick it into the desired enclosure.

The isos and springs aren't perfect garbage disposals but I havnt had mold problems since I've heavily included them in my enclosures.
 
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