Performance of Plastic Plumbing and Electrical Products in Fire Resistive Assemblies
Authors: Zicherman JB 
Published: March 2009

The plastic pipe, tube, and conduit products used in the United States evolved from transplanted European technologies over the past 30 years. Though originally only used in non-fire rated construction, different versions of these products have qualified for use in a variety of fire rated assemblies and building types after appropriate fire endurance tests. End uses for these products include electrical power, signal distribution, and various plumbing and mechanical applications.

Plumbing systems showing acceptable performance in fire resistive assemblies include drain, waste, vent, and supply piping (domestic hot and cold water, sprinkler piping). Approved electrical applications include PVC-based rigid non-metallic conduit and a flexible polyvinyl-chloride (PVC) tubing product called electrical non-metallic tubing. Tested approaches available to safely install plastic pipe, tube, and conduit include passive and active fire stopping systems based on insulations, intumescent systems, and even mechanical “cut-off” devices for thermoplastic piping systems. Fire test results for these products and systems, and the designs that resulted from those testing programs, are widely available. Plastics used to manufacture these products include PVC, chlorinated PVC, acrylonitrile-butadiene-styrene (ABS), poly-butylene (PB), and polypropylene (PP).

Fire risk assessments of potential performance of these products must take into account properties of the resin-polymer systems involved, the nature of the product itself (that is, drain, waste, and vent versus supply piping versus electrical conduit or tubing), where the product is installed (for example, within a cavity wall versus penetrating or encased in a slab), and the type of installation detailing used. Because of the number of possible combinations for end use, analytical approaches based on (1) standard test results, (2) field data on fire performance of the plastic pipe, tube, and conduit products, and (3) fire resistive assemblies into which they are installed all contribute to inferences drawn in conducting hazard assessments.

Specifically, this paper reviews information available to assist in preparing more specialized risk assessments for these products than the general studies cited above, under foreseeable, end use configurations in fire resistive assemblies. An attempt has been made to utilize approaches suggested for general fire hazard assessment procedures that have been under extended study within the ASTM Committee E-5 on Fire Standards over the past several years, but which have not reached the status of standards.

Most field performance data on plastic pipe come from residential occupancies where these products have been used for over 20 years, and where they constitute 95% of pipe installed. In addition, there have been numerous installations in non-combustible buildings (including high rises) here and outside the United States. This database represents a large population for evaluating the fire risk associated with using plastic piping products. The residential data are most interesting because (1) numerically, they represent the largest number of installations, (2) this occupancy type is the most fire prone, based on frequency of occurrence, and (3) these structures are constructed using the least sophisticated building technology. Similarly, electrical tubing and conduit products (havin g met standard fire endurance test conditions) have been used widely in the field without adverse effect since their incremental acceptance into the National Electrical Code (NEC) over the past decade.

For the above reasons, the three model building codes most widely used in the United States (which themselves represent an ad hoc risk assessment process) have accepted these products after requiring demonstration of both acceptable fire performance and availability of reasonable installation methodologies.