This Common Product describes a black single-ply roofing membrane constructed from ethylene propylene diene monomer (EPDM) rubber. EPDM membranes are manufactured through a calendaring process that ensures the finished membrane is watertight. It is then vulcanized, which generates crosslinks between the polymer chains. This makes it a thermoset material in contrast to PVC and TPO (thermoplastic polyolefin) membranes, which are both thermoplastic. Although non-vulcanized membranes are available they are beyond the scope of this Common Product. EPDM membranes are traditionally black in color, but white EPDM membranes are also available. In the latter, carbon black is replaced by titanium dioxide. While white EPDM membranes are often recommended to increase solar reflectivity, black membranes are sometimes recommended for cooler climates that have a higher percentage of heating days relative to cooling days. In addition, black EPDM membranes that are ballasted (loose laid with gravel) have lower rooftop temperatures than membranes that are mechanically attached or attached with adhesives (fully adhered). 

EPDM membranes can contain a scrim within the membrane for reinforcement or can be non-reinforced. Reinforced membranes are recommended for both fully adhered and mechanically fastened systems. Unlike other types of single-ply membranes the seams cannot be heat welded, so they must be joined with either a liquid adhesive and sealant or with seam tape and a splice primer. These products could add additional hazards not considered in this Common Product. 

In the past, some EPDM roofing membranes included brominated flame retardants. While the sources reviewed suggest that industry has moved away from the use of halogenated flame retardants, there is currently very little disclosure on the specific flame retardants used in these products. Consequently, the use of halogenated flame retardants is still possible. Products are advertised as fire retardant may contain additional flame retardants beyond those captured by this Common Product.

A historical version of this Common Product is available here: https://pharosproject.net/common-products/2214466