Why do divers need to spend time decompressing if they’re in pressurized suits?

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Astronauts and people in airplanes can just sit in a pressurized suit or cabin and come down back to Earth without any trouble, but for some reason divers need to slowly resurface even though they’re still only feeling one earth atmosphere in their suits and undersea chambers. Why do nitrogen and other gasses build up if the divers are only under one atmosphere of pressure?

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What divers are you talking about? A standard wetsuit is not at all pressurized.

Planes and spaceships are pressurized *relative to the outside environment,* where pressure is so low humans cannot remain conscious. Air pressure on board is almost always lower than atmosphere at sea level, since large pressure differences create stress on the hull and can contribute to structural failure.

Ordinary SCUBA diving suits are not pressure sealed. Divers experience much more than one atmosphere of pressure.

Regardless of their suit being water tight or pressurized (which is a whole other conversation) its the issue of their air supply. Try to think about their tank. If you want to put more than a few breaths worth of air in there you have to pressurize the hell of out the gasses going into the tank. As you breathe in that compressed air it gets into your blood stream and stays a bit compressed because of the pressure of the depth you’re at. The deeper you are the more weight of the water pushes on you and keeps those gasses compressed. As you ascend the pressure decreases. Those compressed gasses in your blood starts to expand. That is why you need to decompress, so those gasses have some place to go as you breathe them out. If you don’t they’ll expand like ice in a garden hose and start wrecking your blood vessels. The suit here is not the issue, the air you’re breathing is.

If they were under 1 atmosphere pressure they wouldn’t need to, no more than a submariner has to.

But a pressurized suit isn’t going to help a diver, the problem is too much pressure already, which causes excess gas to dissolve in your blood and needs decompression time to come out again. What you need is a rigid, pressure resisting enclosure, ie a submarine with manipulators.

A spacesuit maintains 1 atm against outside vacuum, the drop in pressure if it ruptured would cause similar gas bubble formation as a diver returning to the surface from pressure at depth

The drop in pressure going from sea level to a pressurized airplane cabin is very small compared to the drop in pressure going from deep underwater back to sea level. It *can* be dangerous for people with certain medical conditions to go up in airplanes though.

That said, divers aren’t under one atmosphere of pressure. I’m not sure where you get the pressurized suit thing from, deep sea divers acclimate to pressure on the way down and on the way back up. Sometimes they’ll be inside submersible diving bells or capsules but those are at the same pressure as the water around them.