Two craftsmen were tasked with installing a water line. Instead of drilling a new wall penetration through which to run their line, they decided to uncover the cap and fireproofing material from an existing, vacated wall penetration they'd decided to utilize. During the course of their work, old insulation material was pushed out of the wall penetration as they were pushing the pipe through.
The material was not noticed or identified as asbestos at the time, but was discovered approximately 7 months following the installation of the line. The craftsman later claimed they assumed since the wall penetration had been capped and fireproofed, then that meant it had been remediated from all asbestos material.
Assume all wall penetration locations could still contain asbestos containing material if the building in question was constructed pre-1980. Wall penetrations are often the most difficult part of a building to completely remove asbestos materials when buildings are being remediated for asbestos.