The Cone Calorimeter: The Most Important Tool in Fire Safety Science

The NIST-invented cone calorimeter is an accurate instrument for measuring fire safety related properties of burning materials. It is used to measure properties such as oxygen consumption, heat release rate, and smoke and toxic gas production. The cone calorimeter has led to reduced deaths by fire through its use in the development of fire-resistant materials and fire safety standards. 

Development 

NIST invented the cone calorimeter in 1982 as a bench-scale, reliable tool to measure flammability of materials using the technique of oxygen consumption calorimetry (OCC), which determines the heat release rate of a fire by measuring the amount of oxygen the fire consumes. 

Heat release rate is the most important thing to know about a fire, as it determines the size of the fire, how quickly the fire will spread, and how rapidly the fire will produce dangerous gases. Methods to measure heat release rate by temperature and gas flow were prone to error, difficult to perform and of low accuracy. Using OCC is easier to accomplish and gives more accurate results.

The relationship between oxygen consumption and heat release rate was recognized by William Thornton of Armstrong College in England (now Newcastle University) in 1917. The need for an accurate means to measure heat release rate for fire safety research was discussed by Harvard University’s Howard Emmons in 1959. In the late 1970s and early 1980s, NIST researchers William Parker and Clayton Huggett provided the scientific foundations necessary for OCC to be implemented for fire safety research. And in November 1982 NIST fire research engineer Vytenis Babrauskas first described the cone calorimeter instrument, and he was assisted by NIST technicians Dave Swanson, Randy Shields and Bill Twilley in its development. 

The NIST cone calorimeter was named for one of its components: the open-ended cone-shaped electric heater. This heater is used to ignite a sample material under test. The test sample rests upon a sensitive scale to measure the sample’s loss of mass during combustion. The products of the fire flow up into an exhaust system where instruments measure the oxygen consumption, and thus the heat release rate, as well as a host of different properties, such as smoke and toxic gas production.

Impact 

The cone calorimeter became the standard test instrument that the world’s fire safety research community uses to select and develop materials to meet regulations, standards and codes for the fire performance of products. It can quantify the fire threats for a wide range of materials, including solid plastics, wire and cable materials, aerospace composites, carpeting, fabrics, furniture and just about any modern material used today.

NIST’s cone calorimeter was in use until 2022. Over its 40-year lifespan, deaths due to fire in homes have been reduced, thanks in part to new fire-resistant materials and safety standards that were developed using the cone calorimeter. 

Cone calorimeters are now commercially produced based on NIST’s original design, and the instrument is used in numerous national and international fire safety testing standards.