Apprentice question
Stop and ask
Stop. Get direction before you touch it.
Do not put heavy point loads on a joist chord without approved structural direction. Hold the load and move to an approved distributed support detail.
['Open-web joists are not generic hanger racks. A heavy exhaust plenum or large duct can twist a bottom chord if the load is placed wrong.', 'Stop adding weight, support the duct safely, and get the foreman/GC/engineer involved. Likely recovery is a structural bridge across multiple joists, panel-point attachment, beam clamp layout, or engineered hanger frame.']