There's something one shouldn't leave home without when venturing out in abandoned places. I'm not talking about the once popular ground spice, Mace that's used for savory marinades for meats and stews. I'm talking about the the chemical Mace (CN) that is an Irritant like Tear Gas. Personally I prefer Pepper Spray over Mace which is an Inflammatory Agent that will immediately incapacitate your Assailant and bring them down long enough to flee. I never leave home without it.
Why do I say bring Mace or Pepper Spray when exploring. This is a defense that can be used towards confrontational Squatters or animals that might be overly aggressive. You never know what you might run into which always heightens the adrenaline when first entering unknown areas.
Many ask: "Why Mace or Pepper Spray? I have a knife!" Simply put, Mace and Pepper Spray is a defensive medium where a knife is offensive. If an offensive weapon is used, (especially against humans) you can get yourself in a lot more trouble than that of just trespassing.
I talk as if I have experience... I really don't and never had the run in with an aggressive Squatter and honestly don't want to ever have to. I do like to be prepared for such situations in the event one arises. However, if I have the gut feeling that I shouldn't enter an abandoned building for the fear something may go wrong, I won't.