inside duct insulation - seal edges??

[jhcrowman]

The return ductwork and the first 3 feet of the supply ductwork (metal) have been insulated inside the duct. Most of the fiberglass I can see inside is covered with a black coating, which I'm assuming will prevent any fiberglass from getting into the air. I can see the edges of the insulation, and they are not covered with anything. For example, the piece of duct that attaches to the Air Handler will have plenty of air blowing on all 4 ends of the insulation. Is this a concern? Will the constant movement of air slowly break off pieces of fiberglass into the air? Should it be sealed, and if so, what should be used?
Thanks in advance!

[vern p]

jh, yes the joints sould be sealed and the first portion of the insulation off the AH should have metal edges protecting all 4 sides per SMACNA Duct standards.

[jhcrowman]

Thanks for the reply.
The inside duct insulation is about 3/4" thick, so I can see the 3/4" edge that is not sealed with the black tar-looking stuff. What should I use to seal that edge with? Tape (if so, what kind), silicone, duct mastic??

[vern p]

if your talking about the joints we always used the same glue used in attaching the insul to the duct but we used a paintbrush on those edges as we installed it if it wasn't done in the shop. Now that 1st leading edge has to have a metal nosing wraping around it covering the entire leading edge