Fire protective clothing and thermal protection performance
Fire protective clothing is used to prevent burn injuries in diverse industrial applications and in fire fighting. However, very often, uncontrolled fires lead to situations, where fire fighters are exposed to extremely high levels of convective and radiant heat and flames. For this reason thousands of fire fighters sustain burn injuries every year. In the USA, injuries to fire fighters have been estimated to cost between 2.8 to 7.8 billion dollars a year. Significant numbers of these injuries occur when energy stored within the layers of the protective equipment are suddenly transferred to the fire fighter, resulting in burn injuries.
Protective equipment is designed to insulate a fire fighter from the thermal environment. A series of protective layers and air gaps prevent the energy of the fire environment from being transferred to the fire fighter. However, if the protective layers are compressed, the energy stored within the material can suddenly be transferred to the user and cause burns[1].
To improve the protection and safety of fire fighters against heat and flames, fire protective clothing is tested to thermal protection performance (TPP). The standard NFPA 1971, Protective Clothing for Structural Fire Fighting[2], addresses a test method for measuring thermal protection and a minimum Thermal Protective Performance (TPP) rating. Its purpose is to measure the time elapsed for convective and radiant heat to penetrate through the composite system – Outer Shell, Thermal Liner and Moisture Barrier – to damage the human skin. The TPP test has also been adopted by ISO as a test method standard (ISO 17492).
The test apparatus consists of two burners angled upward toward the center face of the sample clothing composite and a panel of super heated quartz tubes is located between the burners to provide a combined convective and radiant heat exposure.