Urban exploration of abandoned/deserted areas and structures, or urbex, is growing in popularity. There are, however, risks. Besides the obvious downside of being arrested or fined for trespassing, there are potentially significant health hazards in entering abandoned structures, particularly abandoned factories. Factories many be contaminated with toxic industrial chemical residues, friable asbestos, inhalable spores from mold, lead- or other heavy metal-based paints, unsafe flooring and stairs, etc.
Here's a link to a news story regarding "exploration" of the old Joliet, IL Prison gone awry:
http://www.chicagotribune.com/suburb...112-story.html