Adam G wrote:The problems arise when you realize that many old and/or abandoned buildings can be harmful and dangerous to explore, I'm mainly referring to asbestos poisoning.
~Adam~
That's why you wear a respirator. It also offers some protection against radon.
Many people make the mistake of using regular painter masks, they might as well be wearing chicken wire on their face.
Other requirements:
A good set of radios for everyone in your party, especially if you split up.
A Maglite and a mini Maglite for a backup, no cheap flashlights, you drop a cheapy one and it breaks you're SOL.
Safety glasses unless you already wear glasses.
A good pair of boots, preferably steel toes with non-slip soles.
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The bigger dangers of urban exploration are collapsing floors, walls, ceilings, etc. and running into people you'd rather not run into, that big Maglite can also double as a weapon in a time of need. Addicts and bums can inhabit those buildings or worse.
Obviously, never go alone, 3 person minimum is a good rule.
Above all use your brain, if it's a big enough safety risk don't do it.