Reduced-scale test to assess the effect of fire barriers on the combustion behavior 

of core flammable materials: an upholstery-material composites case study

Mauro Zammarano, J. Randy Shields, Shonali Nazaré, Ickchan Kim, Isaac Leventon, Anthony Hamins, 

Rick Davis

Flammability Reduction Group, Engineering Laboratory, National Institute of Standards and Technology

(NIST) , USA.

mzam@nist.gov

Keywords: reduced-scale testing, cone calorimeter, pool-fire

NIST has developed a reduced-scale test (“Cube” test) that aims to capture the effects of fire 

barriers on the combustion behavior of composites in which the core material is the primary fuel load. 

Upholstery material/composites employed in residential upholstery furniture (RUF) are used here as a 

case study. RUF are multi-component products including cover fabrics, interlinings, padding materials 

and frame elements in which the core material is the primary fuel load. The core material in RUF is a 

padding material (e.g., polyurethane foam and/or polyester fiber fill). Interactions among the 

combustion of the components make the prediction of real-scale performance based on singlecomponent performance very challenging, if not infeasible. 

RUF combustion is further complicated by the gradual collapse of the core material during 

combustion, and the formation of liquid products that ultimately drip and accumulate under the burning 

item to form a pool. Such a pool can ignite to form a pool-fire. Formation of a pool-fire under burning 

upholstered furniture can dramatically increase the peak heat release rate (up to roughly one order of 

magnitude) and thereby increase the fire hazard. The Cube test is a modified cone calorimeter test

designed to identify the tendency of composites with a flammable core material to form a pool-fire. An

exploded schematic and a photo of the specimen and specimen holder are shown in Fig. 1.

Figure 1. Specimen and sample holder: (a) exploded schematic and (b) photo of the assembly.

(a) (b)
A cube-shaped piece of flexible polyurethane foam (nominal uncompressed length of 106 mm) 

is used as core material. Top and bottom barrier layers (e.g., cover fabrics, fire barriers, interliners, and a 

combination thereof) cover the top and bottom faces of the cube, respectively. The side walls around 

the core material are insulated. The barrier layers are sealed in place by compression between a metal 

liner and the top/bottom frame; metal springs ensure well-defined compression in repeated tests.

Various barrier layers and core materials can be easily combined in the specimen holder to represent

the construction of real-scale RUF cushions.

Fig. 2 shows a composite picture (wide view on the left, top view on the top right, and bottom 

view on the bottom left) for a given sample at the time of pool formation (Fig. 2a) and at the time of 

peak heat release rate (Fig. 2b).

Figure 2. Composite picture for a given sample at the time of: (a) pool formation; and, (b) peak of heat 

release rate. The heat release curve (white line) is shown.

On-going research is intended to quantify how better performing upholstery materials in the 

reduced-scale test (a lower likelihood of developing a pool-fire with its associated relatively large peak 

heat release rate) are related to the performance of the same upholstery materials when tested in fullscale as an actual RUF item.

(a)

(b)