Samuel L. Manzello, Thomas G. Cleary, Jiann C. Yang
Urban-wildland fires have plagued the United States for centuries. Embers are produced as trees and other objects burn in urban-wildland fires. These embers are entrained in the atmosphere and may be carried by winds over long distances. Hot embers ultimately come to rest and may ignite surfaces far removed from the fire, resulting in fire spread. Understanding how these hot embers can ignite surrounding surfaces is an important consideration in mitigating fire spread in communities. This study addresses the ignition propensity of a surface after contact with hot embers.The experimental effort consisted of investigating the ignition of surfaces as a result of impact with burning embers. Embers were simulated by machining wood into small pieces of uniform geometry. Ember simulation was necessary since it is difficult to capture and characterize embers from an actual burning object. Embers were suspended and ignited within the test cell of the FE/DE apparatus. The Fire Emulator / Detector Evaluator (FE/DE) was used to investigate the influence of an opposed airflow on the ignition propensity of a surface. The embers were released and imaged using a digital camera as they impact upon the test surface. Duff as well as man-made materials was employed as test surfaces and the moisture content of the materials was varied. The impact velocity of the burning embers was varied and its influence on the ignitability of the test sample was assessed. The total number of embers deposited upon a surface was varied to assess the influence of multiple ember contact on ignition propensity. Results of this study will be presented and discussed.