Talk:Plenum cable
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While materials used in plenum spaces may not actually require or contain fire retardant additives based on the selection of material, all materials used in plenum spaces must meet rigorous flame spread and smoke requirements as listed in NFPA 90A.
The testing of primary plenum construction materials is conducted under NFPA 255 (ASTM E84) in the Steiner Tunnel and materials are to be considered non-combustible or limited combustible. Supplementary materials found within the plenum spaces must meet similar standards as identified in NFPA 90A. Wire and cable used in plenum spaces (i.e. plenum cable) must meet flame spread and smoke requirements established in NFPA 262 and identified in NFPA 90A.
For specific flame spread and smoke requirements based on the plenum application, the reader should refer to NFPA 90A, Standard for the Installation of Air Conditioning and Ventilating Systems. Depending on the AUthority Having Jurisdiction (AHJ) and the Building Code in use, various editions may be called out for local enforcement. The last published NFPA 90A editions were 1996, 1999 and 2002; the 2005 edition was held by the NFPA Technical Committee and was not issued pending further review in 2008.
As of the 2005 standards cycle, toxicity of materials used in plenum applications has yet to be considered or deliberated at any length. Public comment has been submitted in both written form and oral testimony in the past cycle. The Chairman of the NFPA Technical Committee on Air Conditioning referred the public comments to the NFPA Committee on Toxicity for further review and study prior to the 2008 standards cycle. The State of California has proposed that certain fluorinated chemicals be listed as potential human carcinigens. While this technical discussion is active, there has been no confirmatory testing at this time relating direct toxicological effects to plenum cable. It has been proposed that FEP materials used in plenum cable decompose at temperatures less than that required for combustion to form potentially toxic gases that could produce lethal effects in areas near fire events, but not actually involved by the fire. These matters are expected to be reviewed fully over the coming years.
[edit] Defintions problem: What really is a plenum or air duct?
This document doesn't seem to make it clear that a plenum can be another word for "air duct".
All buildings that use forced-air or convection-based heating and cooling contain plenums, as the ducts themselves.
A plenum is not necessarily the air-space above a drop ceiling, and you don't need a drop ceiling to have plenums. The air ducts in a single-family home are plenums.
Very old and historic structures may have plenum cable directly installed in their air ducts, because opening walls may be too difficult or expensive, and surface cable is unacceptable and/or unattractive.
I find it interesting that non-plenum cable is permitted in the living/occupied area of a building. The living area is also an air-circulation space, probably more than the ducts themselves.
Also, a strange exception to this definition is the convection-heating concept of two rooms, one above the other, with a grated hole joining them. Presumably there is no plenum there and the rooms themselves are used as the ducts. Is the upper room a plenum for the lower, or the lower room a plenum for the upper?
If these two convection-heated rooms are slightly separated by a thick midfloor, is a plenum created when two grates are used, to enclose any small tube-like space, even six inches long, that links the two convective-heated spaces? If one grate is removed, does the plenum/duct disappear?
DMahalko 13:02, 27 October 2007 (UTC)
