Ключевые слова: abandoned, air, building, circulation, collector, concrete, construction, corridor, danger, dark, deep, dirty, duct, ducting, ductwork, dwelling, engineering, exploring, factory, habitation, heat, heating, heating duct, heating network, homeless, industrial, industry, inside, line, main, metal, mystery, passage, pipe, pipeline, power, round, rusty, sewer, steel, subterranean, system, technical, temperature, tube, tunnel, underground, urban, ventilation, warm,