On Tuesday morning, an environmental inspector from a firm hired by the district discovered what appeared to be asbestos debris at the bottom of an air shaft. Later that day, district officials asked Roseman to take a look. They used binoculars and flashlights to peer about 60 feet down the shaft. They noted heating pipes with asbestos insulation and determined that the debris was likely asbestos. It is unclear how long it had been there and whether any fibers had moved to other parts of the building via the heating system, Roseman said.