@Zee Abbas
Thanks Zee. Are these dampers accessible externally to adjust or it requires opening up the ceiling?The tenant who sealed the vents during winter enjoyed the free cooling coming from the vents with very little electric bill for the 2020 summer. He had much higher cooling needs than us above his apartment and rejected when we offered him a window ac and was literally driving our ac for his own needs.He even asked me during summer if there is any way to optimally adjust the pressure of air flow as per his needs in one of his bedrooms.
Fast forward during winter he closed the vents in his bedroom and another one in the living room that comes before his bedroom.
Now the same bedroom which once had a high pressure air flow has virtually no airflow makes me wonder if there is a duct burst or duct got pinched somehow? Ideally i think that unit must have the highest airflow pressure because it is at the same level as the furnace. Who can help me best diagnose this problem? Are there any contractors who specialize in diagnosing issues in duct without ripping the ceiling?