The impacts of thermocouple insulation failure on the accuracy of temperature measurement data in forensic fire-death scenarios—Part II: Low electrical resistance and contamination

Abstract

Part II of this two-part article investigates the impact of thermocouple insulation failure on temperature measurement data in forensic fire-death scenarios. Two different models of glass fiber-insulated thermocouple wires (GG-K-24-SLE and HH-K-24 from Omega Engineering) were passed through a ceramic kiln at temperatures up to 1093°C to measure an ice bath at a constant 0°C. In a separate experiment, the same two models of thermocouple wire plus a BLMI-XL-K-18U-120 mineral-insulated metal-sheathed thermocouple probe were passed through a wood pallet fire to measure an ice bath. In the ceramic kiln, the effect on measurement errors was determined for short vs. long exposure lengths and clean insulation vs. insulation contaminated with pork fat. Glass fiber-insulated thermocouple wires showed severe failure in both experiments, with errors ranging from −270°C to almost 2200°C. The metal-sheathed probe showed no evidence of insulation failure and continued to accurately measure the ice bath temperature within expected margins of error around 0°C. This study highlights how exposure of inadequate thermocouples to fire-level temperatures produces severe errors in temperature data. Consequently, it will not be possible to use this data to draw any accurate conclusions about the effects of fire exposure to human donors or animal proxies.