Ignition Vulnerabilities of Combustibles around Houses to Firebrand Showers: Further Comparison of Experiments

Suzuki, Sayaka; Manzello, Samuel L.

doi:10.3390/su13042136

Cited by 14 publications

(4 citation statements)

References 41 publications

(58 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The three fire spread mechanisms that are most often connected to structural ignition and fire spread include [3,4,5,6]:…”

Section: Introductionmentioning

confidence: 99%

NIST Outdoor Structure Separation Experiments (NOSSE) with wind

Maranghides¹

2023

View full text Add to dashboard Cite

The NIST Outdoor Structure Separation Experiments are part of the NIST Structure Separation Experiments project, which is designed to assess structure-to-structure fire spread in the wildland-urban interface. In the first phase of this project, fire exposures from small source structures (sheds) were quantified in terms of mass loss rate and peak heat release rate in the absence of wind. The performance of a target structure representing a residential façade was assessed in response to exposures from a variety of sheds (differing in construction, size, and fuel loading) and separation distances. These experiments were conducted indoors at the National Fire Research Laboratory at NIST. The knowledge gained from the indoor shed burn experiments was used to develop the outdoor shed burn experiments.This report describes a series of outdoor shed burn experiments conducted at NIST to study the effects of applied wind on thermal (radiant and convective) exposures from variety of sheds to a target structure. The results were used to determine the minimum Structure Separation Distance (SSDmin), which is defined as the shortest distance between the source (storage shed) and target structure (residence) to prevent ignition and flame spread. Experiments were conducted with combustible (wood) and noncombustible (steel) sheds, each containing a set of wood cribs and ignited to generate typical radiative and convective heat exposures to the target structure. The target structure was an assembly including an exterior wall with a window and a roof with a vented eave. Effects of shed orientation, shed size, SSD, and shed type on thermal exposure to the target structure were studied. The thermal exposure was quantified in each case by measuring the peak heat flux and temperature at the target structure. Based on target structure performances due to thermal exposure from the burning of different source structures, a SSDmin was identified. The experiments in this study demonstrated good reproducibility of experimental data. The wind had complex effects on the burning behavior of wood sheds, affecting flame lengths and convective heat transfer to the target structure. For combustible sheds, the peak heat flux measured at the target structure corresponded with the total amount of fuel was not affected by orientation (i.e., door opening facing downwind or upwind). In the case of steel sheds with the door opening facing the target structure, the applied wind had minimal or no effect on thermal exposure to the target structure. The steel sheds contained the fire effectively - thus reducing, but not eliminating, the thermal exposure to the target structure. For the scenarios evaluated, peak heat flux at the target structure could be reduced by half by changing the orientation of the door opening for noncombustible sheds. The SSDmin was identified as 10 ft for combustible and noncombustible sheds with floor area less than 26 ft2 in scenarios with a fire hardened target structure. For sheds with floor area between 26 ft2 and 64 ft², the minimum SSDmin was found to be 15 ft. Because the local winds during a WUI fire are unpredictable, SSD should be omnidirectional, i.e., the same SSD in all directions. 12 out of the 13 experiments were conducted with a fire hardened target structure. Experiment conducted with a non-fire hardened target structure to demonstrate the effectiveness of fire hardening revealed that the non-fire hardened structure ignited within 6 mins when exposed to a Very Small wood shed with total fuel of 212 kg and SSD of 10 ft. With similar thermal exposure, and SSD, the fire hardened target structure exhibited minimal thermal damage and significant ignition resistance. Acknowledging the limitations of the experimental series, implementation of the minimum separation distance identified from the experimental measurements in this study is expected to improve community resilience to WUI.

show abstract

“…The three fire spread mechanisms that are most often connected to structural ignition and fire spread include [3,4,5,6]:…”

Section: Introductionmentioning

confidence: 99%

NIST Outdoor Structure Separation Experiments (NOSSE) with wind

Maranghides¹

2023

View full text Add to dashboard Cite

show abstract

“…Such wildfires can occur in any type of combustible material, but commonly start with FF by natural (for example, lightning strikes) or artificial cause (for example, bonfires, uncontrollable prescribed wildfire, damaged or sparking power lines, arson). Essentially, the problem of wildfires in WUI is a problem of structural ignition, and the best approach aimed at reducing its severity is to reduce the potential of structural ignition [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Modeling of Wood Surface Ignition by Wildland Firebrands

Матвиенко

Касымов

Loboda

et al. 2022

Fire

View full text Add to dashboard Cite

The probability of structural ignition is dependent both on physical properties of materials and the fire exposure conditions. In this study, the effect of firebrand characteristics (i.e., firebrand size, number of firebrands) on wood ignition behavior was considered. Mathematical modeling and laboratory experiment were conducted to better understand the conditions of wood ignition by a single or group of firebrands with different geometry. This model considers the heat exchange between the firebrands, wood layer and the gas phase, moisture evaporation in the firebrands and the diffusion gases of water vapor in the pyrolysis zone. In order to test and verify the model, a series of experiments to determine probability and conditions for ignition of wood-based materials (plywood, oriented strand board, chipboard) caused by wildland firebrands (pine twigs with a diameter of 6–8 mm and a length of 40 ± 2 mm) were conducted. The experiments investigated the firebrand impact on the wood layer under different parameters, such as firebrand size and quantity, wind speed, and type of wood. The results of experiments showed that the increase in wind speed leads to the increase in probability of wood ignition. Based on the received results, it can be concluded that the ignition curve of wood samples by firebrands is nonlinear and depends on the wind speed and firebrand size as well as their quantity. At the same time, there is no ignition of wood samples in the range of wind speed of 0–1 m/s. The ignition of wood is possible with a decrease in the distance between the firebrands with a decrease in the firebrand length. This result agrees more closely with the model.

show abstract

“…The NIST Dragon has experimentally revealed the vulnerabilities around houses in full‐scale experiments considering “flying firebrands” 37‐39,42‐47 previously seen in postfire survey 48‐51 . The experimental results from the NIST Dragon were used to revise the California Building Code Chapter 7A and develop ASTM test methods 52,53 .…”

Section: Introductionmentioning

confidence: 99%

“…The size of firebrands is matched with firebrand data from burning trees or burning structures by changing feeding materials. 40,41 The NIST Dragon has experimentally revealed the vulnerabilities around houses in full-scale experiments considering "flying firebrands" [37][38][39][42][43][44][45][46][47] previously seen in postfire survey. [48][49][50][51] The experimental results from the NIST Dragon were used to revise the California Building Code Chapter 7A and develop ASTM test methods.…”

Section: Introductionmentioning

confidence: 99%

Toward understanding ignition vulnerabilities to firebrand showers using reduced‐scale experiments

Suzuki

Manzello

2021

Fire and Materials

Self Cite

View full text Add to dashboard Cite

Summary Over the past few years, the large outdoor fire problem has been a growing concern throughout the world. It is recommended to clear the combustibles around homes and within communities to avoid potential loss of properties, as firebrand shower ignition is a dangerous threat. One of the common combustibles around homes is mulching materials. A reduced‐scale experimental protocol was developed to study ignition of mulching materials by firebrands and resulting impact to adjunct wall assemblies. Reduced‐scale experimental results were compared with full‐scale experimental results. Specifically, two trends were of interest in the comparisons. First, the ranking of the ease of ignition for various mulch types from exposure to firebrand showers. Second, if a given mulch type ignited from exposure to firebrand showers, was the resulting mulch bed fire able to ignite the adjacent wall assembly. The reduced‐scale experimental results captured some of these trends observed from full‐scale experiments but not completely. The findings still suggest that the reduced‐scale experiments may give insights into how easily different mulch beds may be ignited by firebrands, as compared to much more costly and time‐consuming full‐scale experiments. While it is interesting to conduct full‐scale experiments, this is very expensive and not always practical, so the authors are devising far cheaper reduced‐scale experiments to provide more in‐depth scientific understanding of firebrand shower ignition of construction components.

show abstract

Ignition Vulnerabilities of Combustibles around Houses to Firebrand Showers: Further Comparison of Experiments

Cited by 14 publications

References 41 publications

NIST Outdoor Structure Separation Experiments (NOSSE) with wind

NIST Outdoor Structure Separation Experiments (NOSSE) with wind

Modeling of Wood Surface Ignition by Wildland Firebrands

Toward understanding ignition vulnerabilities to firebrand showers using reduced‐scale experiments

Contact Info

Product

Resources

About