MH-60 HVAC Muffler

So pilots report during a post-flight that the HVAC system had low output at the vents, with some banging and whistling throughout the system. Go to tear out some of the ventilation to check for any damage or blockage and I think this might have been the problem! Turns out it's the sound-proofing foam that's used inside the HVAC muffler system. Combination of time-in-service and changes in temperatures, the glue securing the foam weakened and got dislodged about 4 feet down the vent tubes, at the 90 degree turn point. And with the force behind the system's air speed and the residual glue still on the foam melting to the sides of the ventilation tube when heated air was applied, took about 20 minutes to finally remove the whole piece of foam. May not be the best design...