Experimentally Simulating Wind Driven Firebrand Showers in Wildland-urban Interface (WUI) Fires: Overview of the NIST Firebrand Generator (NIST Dragon) Technology

Abstract

Evidence suggests that wind driven firebrand showers are a major cause of structural ignition in Wildland-Urban Interface (WUI) fires. While firebrands have been researched for over four decades, prior studies have focused mainly on how far firebrands fly and are of limited use to design firebrand resistant structures. The NIST Firebrand Generator (NIST Dragon) is an experimental device that can generate a firebrand shower in a safe and repeatable fashion. Since wind plays a critical role in the spread of WUI fires in the USA and urban fires in Japan, NIST has established collaboration with the Building Research Institute (BRI) in Japan. BRI maintains one of the only full scale wind tunnel facilities in the world designed specifically for fire experimentation; the Fire Research Wind Tunnel Facility (FRWTF). The coupling of the NIST Firebrand Generator and BRI's FRWTF is leading to progress in assessing vulnerabilities of structures to a firebrand attack. A brief summary of key results to date using the NIST Dragon installed in the FRWTF are provided in this paper as well as a description of the NIST Dragon's LAIR (Lofting and Ignition Research) facility. The Dragon's LAIR is the only experimental facility capable of simulating continuous wind driven firebrand showers at bench scale. In addition, a detailed description of a new experimental apparatus is presented here for the first time. This device is known as the NIST full scale continuous feed Firebrand Generator (the NIST continuous feed Dragon).When installed inside BRI's FRWTF, the full scale continuous feed Dragon, an improvement of the NIST Dragon, is the first and only experimental apparatus capable of generating, continuous wind driven, controlled firebrand showers that may be directed onto full scale building elements. This paper closes with a discussion of future research needs and opportunities for collaboration.