Furnaces may have two plenum areas. One where the air supply ducts are connected to distribute heated or cooled air to the various rooms. The other plenum area is an area where the return air duct is connected to under the furnace, often part of the platform the furnace sits on. It is the later plenum area that sometimes has exposed fiberglass insulation that may be a health issue.
The concern with exposed fiberglass insulation in the plenum is that as the air passes over the exposed fiberglass, that small fiberglass fibers or particles may be drawn into the air flow and end up being circulated through the house.
Breathing air into ones lungs, containing these microscopic particles can be un-healthy or cause respiratory issues.
Correction of issue
Normally this issue can be easily corrected by several different methods.
1. Cover the fiberglass properly with drywall or other material that will safely seal off the exposed fiberglass.
2. Remove the fiberglass insulation from the plenum area. Once completed, clean and vacuum the area. Also, proper cleaning of ducts should be considered.
Who to consult? HVAC contractors and qualified handymen.
Home owners usually can remove or cover exposed fiberglass insulation in the plenum area. HVAC contractors and qualified handymen can likewise handle this task easily and inexpensively.