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Plenum ratings

In most commercial buildings, the area above the suspended ceiling is used as an air plenum. Model codes restrict the surface burning characteristics of the materials that can be installed in air plenums. Various tests are used to evaluate the surface burning characteristics of constructions materials. The most common requirement is to restrict materials permitted within plenums to those meeting a 25/50 flame spread/smoke developed when tested in accordance with ASTM E84.

The Corzan® Pipe and Fittings ICC report for use in plenums identifies that:

  • Pipe must bear the manufacturer’s name or trademark, test standards, rating and the ICC-ES PMG listing mark.
  • Fittings must bear manufacturer’s name or trademark, nominal size and a third party certification mark. Packaging must be marked with test standard, rating and ICC-ES PMG listing mark.


When installing, the pipe and fittings must be installed in accordance with the manufacturer’s instructions and the applicable code. Installation of pipe and fitting within ducts and plenums shall be in accordance with Section 602 of the IMC or 602.0 of the UMC. The following ratings were obtained and have been found to meet the 25/50 flame spread/smoke developed requirements:

  • 1/2″ – 6″ water-filled Corzan pipe and fittings have a flame spread index of 0 and a smoke developed index of no more than 20.
  • 1/2″ – 2” dry Corzan pipe and fittings for condensate lines have a flame spread index of no more than 0 and a smoke developed index of no more than 20.


Read the full summary document here: Corzan CPVC Pipe and Fittings Listed For Use In Plenums

Read the full ICC-ES report here: ICC-ES Full Report on Corzan CPVC Pipe and Fittings

Read the full IAPMO ASTM E84 Evaluation Report here: IAPMO ASTM E84 Evaluation Report on Corzan




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