Lol. I truly love these types of sites. Not only is it epic that people have the same questions i have, but some of the answers are brilliant.
That said.. i don't believe anyone actually answered and explained your question well.
Now I have to ask you to bear with me and hear me out.. because, for one, I have to break your question up to answer it fully. And two, I don't actually know WHY I know any of this.
Assumption: Assume I can, relatively easily, create a tank of air compressed until it is almost solid.
Can this tank be considered a bomb?
No, oddly enough.. for several reasons.
Now you have to understand certain things. An explosion is different from a deflagration, burning, or oxidation. A high explosive will create a supersonic concussion wave that is what does most of the damage near the explosion. This is because the explosive is not only decomposing - breaking into smaller and smaller chemicals that take up significantly more space, but rapidly heating, which adds energy as the wave travels.
A fluid leaving a container will almost never be supersonic. All the energy is put in up-front and only so much matter can escape a container at once. This means if we were in a spaceship and I shot a small hole in the hull, no one would get sucked out.. even if i significantly increased the pressure in the ship.
And while the container would begin to rupture further, as Ash said previously, it has no brisance since the container could ALREADY hold it.. You'd essentially create a rocket.
(Hint: look up ruptures in hot water boilers)
Would this tank be a weapon?
oh hell yes.
We already know humans are wildly fragile. I also need not tell you that if you were using this tank as a missile, no meat creatures would be coming out intact.
But let's say i could make the entire container fail catastrophically...
Well.. if you were standing next to, say, a tank that held a cubic meter of liquid air at room temperature.
You would not be ok. Liquid air is about 710 times more dense than gaseous air. As this sublimated, you'd be splashed by liquid that was rapidly draining heat to expand. In a neat trick of physics, it would boil off your skin, but any that got in your clothing will freeze chunks off your skin..
Not that you'd notice. The localized pressure burst will not only blast you clean off your feet, but it has ruptured your eardrums and quite possibly your eyes. That is.. assuming you weren't struck by a piece of the shell or a small object nearby as they would be moving at epic speeds.
Just note that this concussive "pop" would have a very, very short range.. literally 1 or 2 meters in the above example.. a one meter cube of liquid air would only expand to a 8.9 meter cube..
Compare that to the thousand-fold expansion of TNT and you see why it can't really be a bomb..
.. well.. as long as you popped it outside.
You see.. once you liquify air, its components settle. You'd get a nice thick layer of Nitrogen in 2/3 of the tank.. and a layer of pure oxygen. The "make the smallest fire into a conflagration and make anything flammable" type of oxygen. Yeah. Hope you weren't smoking when it went off.
But worse.. if you popped a few dozen of these babies in an enclosed building.. it would not be ok.
too long; didn't read
No you can't technically make an effective bomb out of JUST compressed air, though it is DEFINITELY dangerous, especially in an enclosed space.
Just compress a flammable gas. Much more fun.