In last time I was investigating about Hi-Press gas. Strange thing that those pipes are used to block people from getting to Shortside Whale, but they aren't even removed if unlock it. As you can see on pipes (there are two, one is located in Phil's base and second one near Love Media Building) it says: Hi-Press Gas and Hot Steam. A steam explosion is a violent boiling or flashing of water into steam (this is from wikipedia).
If steam explodes in water why one pipe seems that it work like outflow pipe? There are two theories:
Rockstar didn't knew for that
Terrorists cut pipe to make explosion.
Also, gas and steam are two diffrent things.
That building may be just used for adjusting heating in hospital (It is located in Carson hospital parking).