We live on the 17th floor of a 21-story high rise and we have recently been experiencing a strong odor that we can't track down or eliminate.

The HVAC system is an Enviro-Tec VH series B fan coil units (size "06"). The smell is musty and sometimes fishy - it comes and goes, though it usually starts after we've had the AC off for a couple of hours. Even when it's off, if we open the windows in one room or the other (there are two vent openings out of both sides of the unit), it seems the air pushes the smell out the other side.

We had an HVAC repairman come by to clean the drain pan and also seal off the space aroudn the pipes where they fit in through the wall - yet the smell still came back. Does anyone have any ideas?