If there is ductwork associated with the heating and/cooling systems, that ductwork will retain the smoke smell and will need to be replaced.

The buyer has requested it be professionally remediated (not just by a GC, which remediation can legally be performed by in FL as we recommended), including potentially replacing all of the duct work, which has not shown any mold.

@Brit HaleIs there existing ductwork?

Greetings BP Family,Can anyone recommend a good HVAC company to install a whole new system plus ductwork in a Baltimore City townhouse?

Same is with the remodeling - I estimate that more than 25% of our rehab cost typically is spent on things inside the walls - new water lines, new sewer pipes, new electrical, sometimes corrections in messed up ductwork.

Look in to mini splits as they as the 110v units often require no electric upgrades nor duct work

As one example, I'm using empty steel barrels to support my vanities, I'll have exposed ductwork and electrical conduit, and I'm just using a clear coat epoxy over the existing container floors. 

Sometimes the HVAC duct work is in the slab as well.  

One that I know of had to replace the entire HVAC system and ductwork because mold had invaded AND the roof. 

All it takes is one dropped item to cause a tenant to start moving a dryer around and the best ductwork can go to hell.Water is also a fortune in my market.