# Would fast decompression take place in a sealed tower on an Everest-sized mountain?

I have a large skyscraper-sized tower built at the summit of the highest peak in my world.

At that height, I am aware that people need oxygen masks and other aids to survive for long and reach the summit. Inside my tower, it's pressurized like an airplane to keep air pressure at sea level through magic sealing the doors.

I want to know if the decompression that would take place if a plane was damaged is a realistic possibility. The kind that would have people and everything not bolted down end up flying out in seconds.

Would the decompression be severe or safe?

Let's start with the relative difference between the the air pressure at sea level and at the Peak of Mt Everest. The atmospneric pressure at sea level is about 3 times that of the ambient pressure at the top of Mt Everest. To put that in context, it's about the same pressure difference as that we see in an inflated car tyre on a car driving around at sea level. So yes, explosive decompression is possible, and it'll make a mess, but assuming your architect isn't an idiot (and why would you build his design if he was), then the damage won't be all that bad. But, let's start with the plane analogy first to figure out why.

First of all, planes don't pressurise to sea level anyway. Their internal atmospheric pressure is usually arounnd 2/3 to 3/4 of sea level pressure. BUT, planes are not built like submarines. If they were, they'd weigh a lot more and carry fewer passengers, so the passenger cabin is one large container rather than being segmented by closeable bulkheads.

Also, planes, by definition, fly really fast. Put both these factors together and you realise that it's not the decompression that causes the real issue with passenger cabin breaches in planes, it's the relative speed of the plane and the subsequent loss of the aerodynamic shape that tends to pull the plane apart, and suck things out of it thanks to the instant chimney style effect.

Relatively speaking, and ignoring wind speeds, your building is travelling at exactly 0 Km/h and is exactly 0m off the ground. That is not to say that a breach isn't going to cause problems, but you don't have the fail badly issue that a plane has to deal with; you're already on the ground and you don't have anything more than latent wind speeds to deal with in terms of damage to the building due to the breach.

On top of all that, your architect, not being an idiot, knows that the building isn't limited to a certain weight so will have built bulkheads into the building that automatically seal off floors in the event of a breach, and ideally also seals off breached sections of that floor. Just like in a submarine or large ship. This means that the volume of air (after the initial rush) that equalises with the outside isn't all that much so while for that section it's going to be bad, it's certainly surviveable with oxygen masks and the like which every section would have as emergency equipment.

Add to that, you actually don't pressurise your building to sea level; you do it to around 11 PSI, or 70 Kilopascals, just like your aircraft. This limits the differential you have to deal with, making your building lighter or stronger (depending on how you manage it).

Why 11 PSI? Because that's (more or less) the lowest air pressure you can go to and have humans breathing the same mix of air that the planet contains by default. Any lower, and you actually have to add oxygen otherwise your humans won't get enough in each breath. In point of fact, Mt Everest is around the same pressure as that which was put in the Apollo mission ships, and that was a pure oxygen environment so that the astronauts could breathe correctly.

(Side point; the amount of oxygen needed by humans isn't a percentage mix of air, it's a volume, measured by what we call partial pressure and this is addressed in many other answers on this site.)

Suffice to say, that pressurising your building to 11 PSI is the most cost effective option because you don't need special atmospheric mixes to keep your population alive and it creates the lowest differential between inside and outside the building.

So; with your pressure differential down to half, bulkheads and emergency breathers readily available, you still have a problem to deal with, but it's not as bad as it could be. Expect the result to be similar to what would happen if you knifed the tyre of a parked car, if that tyre also contained random trinkets (as a scale model of your building of course).

• You're wrong about 11 PSI being the lowest pressure humans can breathe in. At 14,000 ft, the pressure is 8.6 PSI, and I've hiked up several mountains that high -carrying a backpack, too :-) Also have flown an unpressurized plane at that altitude. – jamesqf Jan 11 at 20:46

A more relevant example: Mythbusters did a bit on explosive decompression. Their model had only one major deviation from reality: no wind. Even when they blew an entire window out Buster (their crash test dummy) would have survived sitting next to it.

Your building won't be subject to tremendous winds, this is a much better model of what happens than the airplane disasters where the wind is the real problem.

And note that oxygen masks are fine even on Everest. Build the walls strong, arrange the doors to blow shut in the face of a blowout, provide oxygen masks like on an airplane.

I just had a a quick google and there are two cases which may interest you.

• National Airlines (NA) DC-10-10 aircraft (N60NA) and

• British Airways BAC-111.

In the NA case, a passenger was sucked out the window and in the BA case, the pilot was half sucked out through the windshield (src: https://www.usatoday.com/story/travel/columnist/cox/2012/11/12/ask-the-captain-is-the-movie-flight-realistic/1699119/).

So while the typical movie scenario is completely unrealistic, it could be possible for a person to be sucked out the door or a window if they were just unfortunate enough to be near it when it is broken or opened while at high altitudes. Of course, after the initial decompression you're only going to need to worry about further damage to the plane due to the wind hitting the opening and not being sucked out since all the pressurized air has already been sucked out.

• It's not primarily the decompression that sucks things out of the plane, but the fact that it's moving at several hundred mph. Same principle as if you have loose papers or other light items in your car, and roll down a window while driving down the highway. – jamesqf Jan 11 at 5:27