We are all familiar with the term “crush limit” when it comes to deep diving – how deep a diver can go before the water pressure increases enough to crush our bodies.
Common thinking would lead us to believe that, when exposed to extreme water pressure at depth, a diver would simply be…well…crushed. That’s not quite accurate, but it is close.
It can be difficult to determine what the crush limit of a particular diver might be, so it’s important to consider multiple factors. Our body is a 60% composition of water and 40% of tissue. The small air compartments in the body are not equally susceptible to getting crushed underwater. Some air spaces like the sinuses, lungs, and middle ear are the easiest to burst. Therefore, figuring out how deep can you dive before being crushed is a must.
Human Crush Depth
Human bones crush at a rate of 11159 kg per square inch. So, to reach a level where the bone starts to crush, we will have to reach up to a depth of 35.5 km. This is quite an ambitious leap, as it is way beyond the deepest point in the ocean.
This means divers won’t simply get crushed by the weight of water, well, they surely have a lot of ground to cover before water tries to kill them.
A basic level of physics is used in determining the volume changes. These calculations help in working out the ease with which the divers air spaces can get crushed. This calculation uses Boyle’s law.
As per Boyle’s law, there exists a linear relationship between pressure, depth, volume, and density in the water. Considering 1 bar is equal to 10 meters, the density will increase one-fold every 10 meters. This means, if the density at the surface is 1X, it will be 4X at 40 meters.
Since water cannot be compressed, all the focus goes to the body’s air spaces. The key to ensuring that the tissues doesn’t get crushed is equalizing. Divers compensate the pressure of static water with the help of equal gas pressure into the air spaces of their body. This has a similar effect as air pressure has on the body cavities. By making this compensation, you are actually preventing your body from giving up and crushing under the immense pressure of water.
Crush Depth for Humans in Feet
As mentioned earlier, the rate at which the human bone crush down is 11159 kg per square inch. This gives you a good 35.5 km depth to go without becoming a powdered mulch. So, if you want to go down in the ocean with nothing more special than a wet suit, then you can reach up to a depth of 1100 feet.
Diving With or Without a Pressure Suit
Just like astronauts need a special suit to survive in the vacuum of space, divers require a suit to save themselves from getting crushed by the massive water pressure. Every diver requires to wear a protective suit to prevent themselves from getting freeze out in the ocean.
The suit also depends on the level of dive depth that a diver reaches. The type of the suit will change with the degrees of crushing.
Without a pressure suit
When we dive without a pressure suit, we allow water to get in touch with our body at every contact point. In such a situation, all that you are need to do is equalize the air pressure in your body’s air spaces. You can use a skin suit or wetsuit for this purpose.
Till the time the water in the diver’s suit does not solidify, the chances of a diver getting crushed is minimal. In such a situation, if you are able to equalize the air spaces of the body, you can prevent the body from getting crushed.
With a pressure suit
A pressure suit is a more advanced way of experiencing diving. Unlike a wetsuit, where your entire body is in contact with water, a pressure suit surrounds you with a layer of air. So you are basically floating in an air bubble underwater.
A diver with a pressure suit requires to ensure the gas pressure in the suit is equal to the pressure exerted by water. Divers who use dry suits are more expert than wet suit divers, and they need to learn how to prevent a situation of suit squeeze as they descend. This is a very sore condition that occurs when the pressure in the suit is not equalized with the pressure of water.
If the suit pressure drops significantly, the gas pressure inside the suit is enough to crush the diver.
With an atmospheric suit
An atmospheric suit is a solid suit that has the ability to endure the water pressure exerted on it. The gas pressure inside an atmospheric suit is 1 bar. Due to the rigidity of the suit, water will not have a crushing effect on the diver.
The depth limit of an atmospheric suit is about seven hundred meters. Beyond this level, a potential failure in the functioning of the suit can kill in diver.
Pressure handling ability of the human body
The human body is mostly made of water. 60% of our body weight is water, remaining is body tissue composition. Theoretically, the salts and minerals in the body cannot be compressed along with the water. As long as the diver is able to equalize the pressure of water and the body cavities, crushing of the body can be avoided.
There isn’t any water mass that has the ability to exert enough pressure to solidify water as well as biomolecule, including the bones. So, what can really kill you underwater is an imbalance in pressures and some carelessness on your part.
Scuba diving is not just fun; it is an intriguing experience for the divers to unravel the hidden mysteries of the ocean. Being careful and following the training instructions will not only help you have a safe adventure but also increase the fun by a thousand times.
My unbounded love for the oceans and everything it has to offer motivated me to pursue my passion and become a professional scuba diving instructor.
I keep reading, exploring, and learning more about scuba diving and the underwater world all the time, so I’m excited to share my knowledge with fellow scuba enthusiasts and hopefully contribute a little to your development as a diver. I want people to fall in love with the oceans with as much passion as I have. Read more about me here.