Fire safety standards are developed to protect the lives of building occupants and are commonly adopted as local residential and commercial building codes. An important fire safety standard in the building industry is known as ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Materials. ASTM International, formerly known as the American Society for Testing and Materials, is an international standards organization that developed, published, and periodically updates E84.
The word insulation is commonly associated with fiberglass building insulation that is installed to the building envelope (walls). Mechanical insulation, on the other hand, insulates building mechanical systems such as pipes, ducts, and equipment. When mechanical insulation is installed within a building’s plenum, the space between a suspended ceiling and the roof, exposed pipe, and duct insulation (plus insulation adhesives) must pass E84’s 25/50 rating system per the International Mechanical Code® (IMC®) 602.2.1.8 Pipe and duct insulation within plenums.
To be “plenum-rated”, an insulation’s flame-spread index must be not more than 25 and a smoke-developed index not more than 50. Mechanical insulation that passes ASTM E84 is also called 25/50-rated. The IMC code requirement suppresses the potential for insulation to spread flame and smoke within a plenum to other occupant spaces through the air distribution system. Insulation tested according to E84 “shall not flame, glow, smolder or smoke” at a minimum test temperature of 250°F (121°C).
It’s also important to be aware that IMC requires that products be tested and pass as a composite assembly. For example, pipe insulation with a PVC jacket or coating must pass 25/50 together (not separately). One final, but critical, point is that duct insulation (wrap and liner) must be 25/50-rated throughout the building interior, not just within a plenum space.
Aeroflex USA’s Aerocel® brand of EPDM closed-cell elastomeric pipe, duct, and equipment insulation is 25/50-rated through 2” [50 mm] thick. To find out more about ASTM E84, please visit https://www.aeroflexusa.com/aerocel-elastomeric-pipe-insulation.
Source: 2021 International Mechanical Code
ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Materials https://www.astm.org/
2021 International Mechanical Code