TPP Animation

Test specimens ( 6 x 6 in.) of each test item are prepared for testing. The thermal resistance of each sample is measured using the CSI Thermal Protective Performance (TPP) Tester according to NFPA 1971 Standard on Protective Ensemble for Structural Fire Fighting; Section 6-10 of the 2000 edition.

The heat exposure is from a combination of a largely convective heat source provided by two laboratory burners and a radiant source provided by a bank of quartz tubes. The gas burners, set at angles to the sample, burn 98% pure methane gas at a flow rate of 135 units on the CSI apparatus. The quartz tubes are adjusted at 48% on the instrument scale. The instrument is calibrated to insure the delivery of an exposure averaging 2.0 cal/cm²·sec (8.4 watts/cm²).

The fabric sample is mounted in a sample holder positioned above the heat source and is protected by a water-cooled shutter before and after the test run. The heat transferred is measured by an instrumented copper disk containing four iron/ constantan thermocouples.

An especially designed data acquisition computer software program provides accurate recordings of the rise in temperature of the calibrated copper calorimeter. The rates of temperature rise, or the slope of the temperature vs. time trace is used in conjunction with the calorimeter constants to compute the heat flux received. A square wave exposure sequence is used so that results can be related to the values obtained by Stoll (1). A human tissue tolerance overlay, obtained by integration of the Stoll curve with respect to time, is used to determine tolerance times to second degree burns. The TPP values are the product of the incident heat flux and the recorded tolerance time to second degree burn (cal/cm²).

Reference
Stoll, A.M. and Chianta, M.A., Method and Rating System for Evaluation of Thermal Protection. Aerospace Med. 40: 1232 - 1238, 1968