Question by Bruce Moss posted 16 Sep 2005
| Plenum Definition|
|I have a buiding with lab areas and within the ceilings the sealed air ducts. Is the area around the ducts considered "Plenum" area?|
Answer by Joseph Golan posted 16 Sep 2005
A plenum area is typically used for the return air of an air conditioning system. If your ducts are only a "supply" then you most likely have a return plenum environment which will require plenum rated cable. If you have separate supply and "return" ducts then the void above the dropped ceiling is not being used for a return air plenum. Another easy way to tell is if you have open grills or grill space around the lighting fixtures then is is most likely a return air plenum.
Sonme locals require plenum rated cable for communication cabling even if it is not renning through a return air plenum space. Please check will your local inspector or the AHJ (Authority Having Jurisdiction for the final say.
Joseph Golan, RCDD
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