I saw in another thread some expert urbexer proclaimed infiltrating active locations is not exploring. Well I beg to differ.
I know many people do this just for the photography creds they hope to gain but each to his own. I have always done this for the adrenalin. Nervousness is your body's way of preparing you. It changes you. It becomes habit forming too. And at least in the U.S.A. wont land you in a P.O.W. camp or left to rot in the bush.
Active location infiltration can be the ultimate rush. By stealth, ruse or disguise, getting in where you're not supposed to be has been one of life's simple little pleasures.
I scouted this large building to the left in this photo from the roof top of another large active building. You can see the lights on where remodeling crews were in there working 24/7. Getting up on this roof was almost as much fun as getting into that one! Was not sure what our excuse would be if challenged because it was a wee hours type deal. Looking back I probably should not have tried it. But it was a rush.