Wildfire Protection Solutions: Comprehensive Fire Safety Strategies

Each year, fires in the wildland-urban interface (WUI)—the area where homes and wildlands meet—have caused significant damage to communities. To enhance firefighter and public safety through effective wildfire prevention techniques, fire blanket protection for wrapping entire houses has been studied in laboratories and during prescribed wildland fires. These fire blankets are designed to prevent structure ignition (1) by blocking firebrands from entering homes through vulnerable areas (gutters, eaves, vents, broken windows, roofs); (2) by keeping homes from directly contacting flames from surrounding combustibles (vegetation, mulch, etc.); and (3) by reflecting thermal radiation from large nearby fires (such as adjacent burning houses or surface-to-crown forest fires) for an extended period. Laboratory experiments demonstrated that two-layer thin fabric assemblies could block up to 92% of convective heat and up to 96% of radiation (with an aluminized surface). A series of proof-of-concept experiments involved placing instrumented wooden structures, covered with various fire blankets, in fires of increasing size. Initial tests included birdhouse-sized boxes exposed to burning wood pallets, followed by wall-and-eave panels in prescribed fires in California's chaparral slopes. Finally, a cedar shed was subjected to a prescribed head fire in the Pine Barrens of New Jersey. These experiments highlighted the successful performance and technical limitations of thin fire blankets in providing fire blanket protection. The key success factors for protecting WUI structures are (1) the heat-blocking ability of the fire blanket, (2) durability under extreme heat and high-wind conditions, and (3) proper installation. Consequently, further studies are essential in advanced material/layer development, effective blanket deployment methods, and strategies for multi-structure protection. 

Introduction 

Housing development in the wildland-urban interface (WUI), defined as the area where homes and wildlands intermingle, is rapidly increasing. Between 1990 and 2010, the WUI was the fastest-growing land use type in the United States, with 97% of new WUI areas attributed to new housing and not increases in wildlife vegetation. WUI fires have caused significant destruction to communities, with the magnitude of damage escalating. For instance, major wildfires in California in 2018 inflicted over $12 billion in property losses. Notably, the Mendocino Complex Fire, the most extensive wildfire on record, burned 459,123 acres, while the Camp Fire destroyed 18,804 structures and resulted in 86 fatalities. Similar to urban fires a century ago, the challenge of wildfires in urban and suburban environments ranks among the leading fire threats today. 

The WUI fire issue is often regarded as a structure ignition problem. An effective approach to addressing this is through the implementation of wildfire prevention techniques aimed at reducing the potential for structure ignition. If these ignition instances can be mitigated, WUI fire damage could decrease, enhancing safety for both the public and firefighters. During a wildland fire, firebrands—such as burning branches and leaves—are carried by the wind and can ignite distant spot fires. Studies indicate that firebrands originating from wildfires or burning structures are a significant cause of structural ignition in WUI communities, and in many cases, the primary cause of destruction is the exposure to firebrands or the heat from flames. Post-fire research suggests that firebrands are a major catalyst for structural ignitions during WUI fires. Additionally, case studies reveal that burning homes can ignite neighboring structures, creating a 'domino effect' of destruction. The likelihood of a structure igniting depends on its characteristics (e.g., roofing material, decks, vents) and the fire exposure conditions (e.g., heat flux from flames and firebrands). 

To reduce risks of home ignition, various resources are available to homeowners and communities. Guidelines such as NFPA 701 provide a framework for assessing wildfire ignition hazards around structures, leveraging concepts like home or structure ignition zones and defensible space. However, the issue of structure-to-structure fire spread in WUI settings has not been as thoroughly investigated as vegetative-to-structure fire spread, particularly in densely populated areas. Recent post-fire analyses have identified structure-to-structure fire spread as critical in overall fire behavior, demonstrating the role of heat fluxes from both flame fronts and firebrands produced by structures in aiding fire spread to adjacent buildings and vegetation. To this end, there is an urgent need to embrace technology-driven solutions that can significantly reduce structure ignition vulnerabilities against firebrand showers and heat flux from flames, especially within high-density housing situations. 

When responding to wildfires that can manifest over days or weeks, the protective duration afforded by fire blankets can vary from minutes to several hours, influenced by factors such as housing density, terrain, and vegetation. In areas of lower housing density, a critical exposure period can last several minutes as a wildfire front passes. The threat of airborne embers from burning vegetation can persist for a substantial time—up to 30 minutes before and after the wildfire front. Conversely, in more densely populated communities, neighboring structures threatened by fire can face risks for over an hour, or even several hours, in the absence of firefighting intervention. 

Currently practiced wildfire prevention techniques include applying aqueous fire suppressants and retardants, such as foams or gels, to structures or their surroundings before wildfires arrive. Aerial firefighting efforts also involve dropping water or flame retardants to combat wildfires. While these methods can cover complex shapes of buildings, their effectiveness diminishes with time as they require proper water pressure for application, which can be hindered by wind. Additionally, foams and gels often lose efficacy due to evaporation over time, despite gels proving more effective than water against thermal radiation exposure. 

In contrast, fire blankets represent a potentially more effective and enduring means of thermal shielding. The U.S. Forest Service has used structure wraps to protect historic cabins from wildfires. Over the past two decades, anecdotal evidence and technical knowledge regarding cabin wrapping have accumulated, indicating that while they function similarly to firefighter safety equipment, fire blanket protection for structures is specifically designed to meet different thermal criteria than human protective gear. Unfortunately, systemic scientific research on fire blanket effectiveness has been limited. 

Although fire blankets have been utilized for fire suppression, existing literature on their performance is scarce, likely due to the lack of comprehensive basic research and sporadic R&D activities primarily conducted by manufacturers. Standards such as ASTM F 1989 and British Standards are available but are not performance-based nor widely certified for fire blankets. Subsequently, the fire blanket industry adheres to relatedflammability standards for testing materials used. While fire blankets are typically employed for smothering smaller fires, they are not recommended for handling liquid fires as they can exacerbate fire spread. Newer types of fire blankets, crafted from heat-resistant fibrous materials, provide improved performance over traditional cotton or wool designs, with some innovative models utilizing non-woven polyester and other composite materials designed to meet fire safety standards. 

Various deployment strategies for fire blankets have been documented in patents, highlighting methods from electric motor-driven systems to manual coverings for containing and protecting structures completely. Comparative research with firefighter protective clothing indicates that advancements in materials and testing methods exist, offering potential insights for enhancing fire blanket protection capabilities. 

The most effectively designed fire blankets may succeed in protecting structures from brief heat exposure during wildfire events. In contrast, longer exposures necessitate better-developed fire blankets that enhance heat resistance and minimize vulnerabilities to structure-to-structure ignitions. Hence, ongoing studies are urgently required to explore advanced materials, innovative blanket deployment techniques, and strategies aimed at multi-structure protection against wildfires.