Air (Pressure) Conditioning

Air conditioning (and also heating) so far is defined as controlling temperature only, and not pressure. Could it feasible and practical to extend the functioning of “air conditioning” to include “pressure conditioning” as well as temperature conditioning, as an airplane flying in the stratosphere does?

Also, what would be the consequences of living in a 2.0 atm indoor environment, with the same relative ratio of nitrogen, oxygen, etc. I’ve heard that people can live in a 90 atm environment, provided that oxygen is only a small part of that mixture of gases (otherwise oxygen toxicity results at a far lower total pressure), and the temperature is, unlike Venus which also has an atmosphere of 90 atm and very little oxygen, probably too little) suitable for humans…is this true? If so, how can biological tissue be so strong as to withstand 1300 lb/square inch…

Finally, what if you were locked in a room where the pressure was set to the standard 1 atm, with the (only) difference being that the 78% diatomic nitrogen gas was replaced wholly by one other gas, say one of the noble gases, the halogens, hydrogen, helium, etc. Is there a rule of thumb as to which gases are toxic or nontoxic, or even more favorable to human physiological functioning than nitrogen?

One consequence of living in a pressurized environment is that your tissues would become saturated with excess dissolved inert gas (mostly nitrogen). Leaving that environment and returning to the normal 1 atm world would require reducing pressure in stages over a period of time, much like extended decompression stops for scuba diving. Failure to do so could lead to decompression sickness (DCS).

Since biological tissue is mostly water and other non-compressible solids it really isn’t effected too much by exposure to increased pressure for a short duration. But there is a risk of dysbaric osteonecrosis (DON) which can occur even in the absence of DCS. There is an association of DON with increased pressure and time of exposure.

The Guinness World record depth for open circuit scuba diving stands at 318.25m (1044.13 ft) but there is a claim to 330m (1082.68 ft). That is only in the realm of about 33 atm of pressure. Still a long way to go to reach 90atm.

Helium should be quite safe at that pressure, though it conducts heat more efficiently so the person is more prone to getting cold. As its density is low it would also alter the voice of the breather giving a Donald Duck voice effect.

Deep divers commonly breath a mixture called trimix, a blend of helium, oxygen and nitrogen. It is usually blended by mixing air (including traces of argon, carbon dioxide, and other trace gases) and helium. Very lean (low O2) mixtures may require more complex blending techniques such as blending from cylinders of pure N2, O2 and He. So long as the partial pressure of the oxygen is about about 0.16 it should be fine to breathe for everyday use at 1 atm.

At higher pressure, helium mixtures can bring on High Pressure Nervous Syndrome. This requires blending some nitrogen back into the mix to even things out. (Sort of like taking some barbiturates to counterbalance a dose of amphetamines.)

Halogen gases (like chlorine, or iodine) seem like a really bad idea. I would think hydrogen might be too reactive in the long run though I have heard of deep dive breathing mixtures that include hydrogen.

As to rule of thumb for which gas to choose… I have heard theories, but cannot find a cite, that the solubility of a gas in fat (myelin sheath) is the root cause of the various neurological effects. Low solubility is better. High solubility brings on more neurological effects.

The engineering of it would be really difficult. Houses would have to be completely sealed. So every house would be a steel box. Every outside door would be an airlock. Windows would have to seal also. I work with some airlocks at work, they leak even with only professionals operating them. Leaks would be a huge problem in a residential situation.

The walls would have to be extreamly strong. In Hvac systems pressure is measured in inches of water pressure. Opening a door with just 0.5 inches of presssure takes a lot of force.

Great Debates? Reported for forum change…

Just for reference 2 ATM is the same as SCUBA diving to 33 fsw. At that depth you wouldn’t need to worry about gas mixes at all. Keeping the pressure around 1.6 ATM would be a better bet, at that pressure (around 20 fsw.) there is no no-deco limit. In other words you could be out of the air lock and into a area of normal pressure in less than a minute, and you could increase the safety by slowing that down more if desired.

Despite the fact that there may be differences of opinion, this actually seems more like a General Question than a debate. (If you folks get too rancorous, the GQ Mods can always send it back.)

Moving to GQ.

Where did you come up with that definition? Air conditioning does include pressure conditioning. Most home HVAC situations are simple enough not to need much consideration in this area, but most commercial and industrial buildings do require it. Hospitals, commercial kitchens, etc. and similar buildings are designed to maintain these pressure zones. Other buildings need proper ventilation for indoor air quality reasons. But as** Snnipe 70E** said, the pressure differences are on the order of a fraction of an inch of water or so.

I think you mean differential pressures between zones whereas the OP is talking about the absolute pressure indoors and does not imply anything about differentials.

The forces involved would be bigger than the forces that ordinary walls and ceilings are designed for. You could have the equivalent of two feet of standing water on your roof, or, worse, the sa,e force trying to lift the roof off.

The Armstrong limit is the air pressure at which water boils at the human body temperature of 98.6 F, and is 47 mm Hg, or 0.0618 atm, and is found at 63,000 feet in the standard atmosphere. The Concorde’s cruising altitude was 60,000 feet (very close to the Armstrong limit), and the interior of the Concorde was pressurized to about 622 mb (equiv. to 1700 m above sea level); the difference in the air pressure at the Concorde’s cruising altitude and the interior of its cabin when flying at that altitude is therefore 620-47 = 575 mb, which is around 0.567 atm.

It’s safe to say that the Concorde is engineered at a high level of tolerance to its cabin bursting due to the pressure on its interior, which would be ~8.34 lb/in2.

So constructing a home that whose walls could withstand the interior pressure being greater by 0.567 atm would most likely be possible, but also very likely to be expensive because of the materials that would have to be used, the quality of construction, etc.

Well, you’d only have to accommodate 0.1 atmospheres to handle any common combination of one weather condition indoors and another outdoors.

The Concorde and other aircraft are adept at holding substantial interior pressures in part because they are rather cylindrical; the loading due to pressure is mostly tensile, and there’s very little in the way of bending loads on a fuselage’s walls due to cabin pressure.

If you want a house to have flat walls and a flat ceiling, the walls and ceiling will have to withstand rather immense bending loads; 14.7 psi of excess pressure (2 atm absolute pressure) on the interior of a room with a 10’ x 10’ floor works out to about 212,000 pounds of force trying to raise the roof. Walls and ceilings will be very thick and made of more than just drywall and 2x4’s with some sealant.

If you’re willing to live in a house that’s spherical, or cylindrical with spherical caps (like a residential propane tank), then the construction will be cheaper.