There are two problems to focus on in this picture. The first is the rampant mold growth on the silver pipe on the left--that's the HVAC system. It's covered in mold and that system is drawing that contaminated air up into the rest of the house.
The second problem is the wooden joist on the right--it has bent in such a way that it is flush with the system closest to the subfloor, but warps away near the bottom. This is placing a strain on the HVAC system and can lead to a loss of energy efficiency over time.