Relevant Standard(s)
NFPA 1971: Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting
(Mandatory in Ontario)
Key Terms Relating to Material Composites
CCHR: Conductive and Compressive Heat Resistance - measures the level of thermal protection in key areas of the bunker suit which are typically subjected to compression (i.e. shoulders & knees)
The test represents time for a temperature rise (24*C) when a source of heat(280*C) and pressure is applied.
NFPA 1971 standard requires a minimum CCHR of 25 seconds.
THL:Total Heat Loss - measures the heat stress reduction capability (or breathability)
The more heat that gets trapped inside a firefighter's bunker gear, the more likely an individual may experience dangerously elevated skin and core temperatures, as well as an increased heart rate. Material systems that provide a higher THL will benefit the f irefighter in the form of more breathable turnout gear.
The NFPA 1971 standard requires a minimum THL of 205W/m2.

TPP: Thermal Protective Performance - indicates the level of protection against both convective and radiant heat
To determine actual time to burn, the TPP is divided in half and the resulting number is the time (in seconds) that human tissue reaches second degree burn in a flash over situation.
The NFPA 1971 standard requires a minimum TPP rating of 35.
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