Be careful using PVC with compressed air.[0] It can shatter into hundreds of tiny daggers flying through the air.
[0] https://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-...
[0] https://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-...
If you hit a water pipe. with a shovel and break it, and your pipe has a rather high 100 psi of water in it, you will regret it: you will get wet, you’ll have a muddy hole, and you will be sad because you have to repair it.
If you compress air to 100 psi, you are compressing it to a rather small fraction of its original volume. So the change in volume is greater than the entire volume of compressed air and is almost as large as the uncompressed volume, so 100 psi * (change in volume) / 2. 1 cubic foot of air compressed to 100 psi is something like 10 kJ. Beware!
If you winterize your irrigation system with compressed air to 100 psi (terrible idea), and you hit a pipe with a shove while it’s still at 100 psi and break it, you will release a lot of energy.
But systems using hydraulic fluid to carry power have something that keeps it pressurized as it moves: that is, something that can supply power. Often very large amounts of power. (So do water pipes that have some form of supply, of course, but the pressures are much lower.)
So if you pressurize fluid in a pipe, you are storing some energy in the compressed fluid. You may also have a lot of energy stored or power available in some other component of the system.
In any event, the type of injury you’re describing seems like more of a velocity issue. When you allow fluid to escape from a high pressure environment to a low pressure environment through an opening that doesn’t have a whole lot of friction, the stored energy converts to kinetic energy. Some basic physics says that a small volume V of fluid has potential energy PV and mass rho * V. Conservation of energy says that, when that potential energy is gone (the fluid escapes), it has the same energy, but now it’s 1/2 m v^2. You can solve for velocity, which scales like sqrt(P).
(The real story is more complicated. Pressure in fast-moving things is a bit messy due to Bernoulli’s Law, and different disciplines use annoyingly different terminology. Static pressure, total pressure, stagnation pressure, just plain old pressure, oh my!)
Water (or air) jetting out of a hose through a tiny hole at even 100 psi is not likely to inject itself into a person.
Schedule 40 is rated for 400-ish PSI but with epoxy, locktite, and some tape, it can go up to 1200. For repeat use, err on the side of underpressure. There's so many people pushing boundaries in "homegunner" circles, but every time I see someone doing it - with a cheek weld - I get the jibblies. "It's . . your face, dude"