Reliability of fire indicators based on the damage differential principle in wildland fire investigation: A laboratory approach

Abstract

Reliable interpretation of fire pattern indicators is essential for wildland fire origin investigations, yet experimental validation is scarce. Damage Differential in the context of this study refers to the measurable changes in combustible and noncombustible objects after fire exposure, enabling the comparison and contrast of fire-caused effects on different faces or zones of artifacts, as described in NWCG PMS 412 (2025, 2016, 2005) and NFPA 921. The principle was quantifiably applied using image analysis and statistical methods (ANOVA) to evaluate directional reliability under controlled wind and fuel conditions. Our approach aims to reduce subjective interpretation by linking observed damage to specific fire dynamics and environmental factors. This study presents laboratory-scale wind tunnel experiments evaluating the directional behavior of commonly used indicators. Statistical analysis using ANOVA revealed that wind speed, fuel load, and artifact orientation each had a significant influence on fire indicators (p < 0.001). Findings show that while indicators can yield reproducible directional cues, their reliability is bounded by specific interactions between fire intensity and airflow conditions. A complementary field-scale study is underway to evaluate fire patterns in operational settings, thereby strengthening the scientific basis for evidence-based wildland fire investigations.