Most air handler units have fiberglass insulation installed on the interior surfaces to provide thermal insulation, absorb sound, and help to provide the quiet operation of the HVAC system. As a whole, if properly maintained, air handler insulation has a long-term life expectancy.
In certain instances, the integrity of the fiberglass insulation will degrade from the highly varied ranges of temperature, humidity and air turbulence. If the air handler insulation is left unrepaired, raw fiberglass fibers and insulation will enter the air handler components and airstream.
Each time you have your HVAC system maintained, the condition of the fiberglass insulation should be evaluated. If the exposed fiberglass fibers are exposed to the airstream, it is best to remove and replace the air handler insulation, or resurface the damaged insulation with an approved HVAC encapsulate.
Remember that the air handler supplies the home with the air that you breathe. It is very important to maintain the highest level of indoor air quality and to always make sure that the air you breathe is as pure as can be.