Experienced explorers are very cautious inside active utility tunnels since pipes can spew boiling hot water or steam from leaky valves or pressure relief blow offs. Most active steam tunnels do not contain airborne asbestos, but proper breathing protection may be required for other respiratory hazards. Most steam tunnels have large intake fans to bring in fresh air and push the hot air out the back, and these may start without warning. Others have concrete floors, bright light, and more moderate temperatures.

Some steam tunnels have dirt floors, poor lighting and temperatures above 45 ☌ (113 ☏). This practice was once called 'vadding' at the Massachusetts Institute of Technology, but students there now call it roof and tunnel hacking. Nevertheless, many of these steam tunnels, especially those on college campuses, have a tradition of exploration by students. These pipes are generally run through utility tunnels, which are often intended to be accessible solely for the purposes of maintenance. Universities, and other large institutions such as hospitals, often distribute hazardous superheated steam for heating or cooling buildings from a central heating plant. Utility tunnel in the center of Zurich, Switzerland Ībandoned sites are also popular among historians, preservationists, architects, archaeologists, industrial archaeologists, and ghost hunters. Many explorers find decay of uninhabited space profoundly beautiful, and some are also proficient freelance photographers who document what they see, such as those who document the infrastructure of the former USSR. Haikyo are particularly common in Japan because of its rapid industrialization (e.g., Hashima Island), damage during World War II, the 1980s real estate bubble, and the 2011 Tōhoku earthquake and tsunami. In Japan, abandoned infrastructure is known as haikyo ( 廃墟) (literally 'ruins'), and the term is synonymous with the practice of urban exploration. Although targets of exploration vary from one country to another, high-profile abandonments include amusement parks, grain elevators, factories, power plants, missile silos, fallout shelters, hospitals, asylums, prisons, schools, poor houses, and sanatoriums. Many sites are entered first by locals and may have graffiti or other kinds of vandalism, while others are better preserved. Ventures into abandoned structures are perhaps the most common example of urban exploration.

Urban explorer falls to death