What is technically destructible on maps?

[peterbill 0]

I am sort of a TBS purist in that once I start my campaign I like to just keep playing, no matter how badly things go.

That being said, I like to know the ROE going into combat. I'll be using CE Edition with FITH active.

I noticed on some of the maps there appear to be gas/petroleum/oil tanks (can't tell exactly what they are holding). If I shoot at them, or if one of my soldiers is standing next to one if it gets hit, will they explode and cause damage to nearby tiles? Will alien AI try to shoot these or destruct environments around my soldiers to kill me? Or do they just aim directly at humans?

I am just asking because I can see this as a strategy, if there is an alien next to a gas tank and I can just throw a frag or something. Also, if it is going to explode, does it happen in real time, or is there a delay like with the frag grenades?

Any other tips anyone has about using the map environments would be awesome. I have been playing XCOM EU for a long time so this game is still very new to me.

Thank you in advance.

[Max_Caine 90]

I haven't played X1 in a long time, so I don't remember what happens with gas tanks. However, I can say that no, aliens will not shoot gas tanks on purpose - just by accident. Unlike like XCOM EU, you can shoot ANY terrain, as there's a force-fire feature, so you can blow holes in walls and use them as entry points etc. 

[Coffee Potato 24]

The only things not destructible are the deep ships and walls of the UFOs. The doors are still destructible. Base walls are also indestructible, but have destructible elements, such as the vents for ambushes.