Originally Posted By: Lance MacNevin
This post was automatically imported from our archived forum.
The following is an excerpt from Technical Bulletin 216R by REHAU, a manufacturer of PEXa piping systems:
"A plenum is defined as an enclosed portion of the building structure that is designed to allow air movement, thereby serving as part of an air distribution system. Plenums can serve as supply, return, exhaust, and ventilation portions of the air distribution system.
"Building codes require that combustible materials installed within air plenums have a flame spread rating of not more than 25, and a smoke developed rating/classification of not more than 50. Pipes that meet these requirements are sometimes said to have a ?plenum rating.?
"The flame spread rating and the smoke developed rating/classification are measured in a laboratory in a standardized test that burns the combustible pipe and measures the speed of flame spread and the volume of smoke developed. USA and Canada have separate, but similar, standards for this test. These standards are:
 ASTM E-84: Surface Burning Characteristics of Building Materials (USA)
 CAN/ULC S102.2-M88: Standard for Surface Burning Characteristics of Flooring, Floor Covering and Miscellaneous Materials and Assemblies (Canada)
"Since these tests use slightly different test procedures, the numbers developed for the same pipe may be different. These numbers are unitless, and are used as index (comparative) ratings of how quickly a pipe burns and how much smoke is developed when a pipe burns.
"REHAU?s RAUPEX plumbing pipes have been tested to both standards by Intertek Testing Services (ITS/Warnock Hersey). With flame spread ratings below 25, and smoke developed ratings/classifications below 50, RAUPEX pipes meet the requirements to be exposed within air plenums for both USA and Canada.
"Therefore, it can be considered that RAUPEX pipes have a ?plenum rating? (check local codes for requirements that may be different)."
These tests are not mandatory requirements for PEX pipes. Each PEX pipe manufacturer may have testing conducted on their pipes, if they choose, to allow use in such applications. PEX pipes so approved are usually marked with the standards: ASTM E-84 / CAN/ULC S102.2M
Commenting on the installation shown in the picture, that is unfortunate installation of the distribution manifold. It is not dangerous and it will function, but craftmanship is poor. We will try to contact the installer and have a special training about installation of these manifolds.
Manager - Heating & Plumbing Technical Services