Fire Technology, Vol. 34, No. 3, 1998 Fire Patterns on U holstered Furniture: Smolder ng versus Flaming P Combustion R. A. Ogle and J. L. Schumacher Packer Engineering, Inc., Naperville, IL AbStTUd In most fire investigations, fire damage patterns provide important clues regarbg the ori- gin and causeof the fire. Historically, many fire investigations have relied on intuition to interpret fire patterns, the results of which have often been inconsistent with scientific principles. NFPA 921. Guide for Fire and Explosion Investigations, which advocatesthe scientific method for forensic investigations, includes a summary of many fire patterns stnd interprets them basedon scientific disciplines such asfire dynamics, heat transfer, and materials science.But IWPA 921 does not addressthe fire pattern that appears on uphol- stered furniture when it is the fist item ignited. In this study, a test program was conducted to determine the nature and extent of fire patterns on upholstered furniture caused by smoldering versus flaming ignition sources. Smoldering fire patterns tended to consist of char zones with a thickness equal to that of the fuel element. Conversely, flaming fire patterns had thin char zones with thicknesses much smaller than the thickness of the fuel element. After a smolder-to-flame transition, rhe fire patterns created by smoldering were rapidly destroyedby the flames and replaced by flaming fire patterns. In nine tests out of ten, the origin of the fire was coincident with the location of a bum- through (a penetration caused by the consumption of a fuel element) in the upholstered furniture item. However, asymmetric flame spread caused by unusual construction fea- tures could lead to bumthroughs in other locations. A bumthrough was observed in all six tests in which a transition from smoldering to flaming fire behavior occurred. Only in the earliest stage of the ignition sequencewill the physical evidence of the igni- tion source-smoldering or flaming-be preserved. Thus, to determine the causeof a fire, the investigator may need to rely on a consideration not only of fue pattern observations but also the human and environmental factors which may have contributed to the ignition event. This is an approach often called system safety. Introduction The purpose of a fire investigation is to determine the origin and cause of a fire. Fire damage patterns provide important clues if their interpretation is based on fundamental scientific principles. The guidance document, NFPA 921, Guidelines for Znvestigating Fires and Explosions,’ provides an excellent intro- duction to the subject. Unfortunately, however, several misconceptions regarding fire damage patterns persist to this day. One such misconception the authors encountered involved interpreting fire patterns on an upholstered sofa, whether the sofa had been ignited by a smoldering source (cigarette) or flaming source.