Uncontrolled decompression is when something inside a sealed space (like a submarine, an airplane, or even a room) loses air pressure quickly. This often happens when the air inside the space is suddenly released, like a balloon popping, and it makes the air pressure equal to the air pressure outside. This can be dangerous because our bodies need air pressure to function and when there isn't enough air pressure, our bodies can't work properly. So, when there is uncontrolled decompression, our bodies may not be able to do what we want them to do, like hold our breath. This can be very dangerous and could even lead to death.