Results 1 to 3 of 3
  1. #1
    Join Date
    Nov 2011
    Post Likes

    Red face Insulation in Plenum Box??

    Hi everyone, hope you'll can give me some insight.
    Our plenum box is approx 37 years old it is insulated inside with some type of black compressed insulation. The problem is that anytime the A/C or Heater come on it will blow some pepper like debris out one of the air duct vent, that air duct is the shortest and closest one to the plenum box so it seems that its the one that gets to blow out that debris, which lands on the furniture directly underneath the vent. The debris looks like black dirt or pepper and when you pick up a piece you can smear it like if it was charcoal.
    Is the insulation disintegrating? Is it possible that this so called black insulation inside the plenum box contains asbestos??
    The air ducts connected to it are all sheet metal and covered with insulation but they seem to be intact and not damaged..........

    We are thinking of replacing the box to see if it resovles the issue.
    I am worried that this whole time its been blowing out asbestos fiber . Any thoughts on this? Thank in advance!

  2. #2
    Join Date
    Jun 2011
    Houston area
    Post Likes
    I would very very seriously doubt it's asbestos. From your description it sounds as if the inside of the plenum "box" is lined with an insulating material and there are various ways of attaching or making it adhere to the sheet metal surface. More than likey the insulation is a stranded and chopped fiberglass with the outer surface dyed black. It can be dyed any color but deep yellow, orangish, red and black are the most common in HVAC applications. The chopped fibers are bound together with short chain polymer resin to create a flexible yet somewhat rigid sheet that can be easily cut and fit to conform to almost any shape.

    You don't give a location or any info as to if this is heat only, cool only or combo of both and there are issues in each of those situations.

    Asbestos, in my experience has a white/gray and sometimes yellow hue and the strands and fibers will feel hard unless it's been ground or cut with a saw or drill resulting in a sawdust like stuff. Again, I'd seriously doubt it really asbestos

    Tell me a little more and I might be able to help you, good luck.
    The picture in my avatar is of the Houston Ship Channel and was taken from my backyard. I like to sit outside and slap mosquitos while watching countless supertankers, barges and cargo ships of every shape and size carry all sorts of deadly toxins to and fro. It's really beautiful at times.....just don't eat the three eyed fish....

    ¯`·.¸¸ .·´¯`· .¸>÷÷(((°>

    `·.¸¸..· ´¯`·.¸ ¸.·´¯` ·.¸>÷÷(((°>

    .·´¯`· .¸>÷÷(((°>


  3. #3
    Join Date
    Nov 2011
    Post Likes
    Thread Starter
    Thank you Cooked, well it happens for both combos of cool/heat.......... I am not sure if we should have the plenum box replaced along with all duct work or just the box itself.

    It looks like the ducts and box are all 1 piece which is probably impossible. The house itself is like 36-37 years old and when I think of having the plenum box replaced or ducts; I wonder if there is any asbestos up there...........

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.