Wildfires are a global issue, with new record-setting events occurring over the last several years. The growth in frequency and severity of wildfires can be attributed in part to an ever-increasing population and subsequent expansion of urban areas and human activity into wildlands. This zone of transition between wildland and human-developed land is termed the “Wildland-Urban Interface” or WUI. In addition to the impact of human expansion, climate change and drought are also contributors to the increasing frequency of wildfires. As we look to the future, the risks of wildfires are expected to increase in wildfire-prone regions and in areas that have been less affected in the past. Building managers and owners need to understand their property exposures, fire risk assessments and prevention measures to improve their structures sustainability and to minimize smoke infiltration.
Wildfire Exposure to Property
Wildfires cause the ignition of structures through: (1) convection and the spread of flames directly to the building, (2) radiant heat transfer, and (3) infiltration and deposition of burning embers into, and on, a structure. The probability that a structure will be exposed to a wildfire depends on multiple environmental factors including potential for ignition of surrounding vegetation, types of fuels, and weather conditions. The primary items considered in assessing a property’s exposure are the possibility of a fire burning near a structure, a fire’s intensity, airborne ember production, and the distance separating the fire and the structure. A hazard and exposure assessment includes the following three steps, predicated on a review of the vegetation (fuels) around the structure:
〉 The need for assessment: An assessment is recommended if there are vegetative fuels that could sustain wildfire spread within proximity of a structure. The Fire Protection District Breckenridge, CO program “Be Ember Aware” states that flaming brands and embers can travel five miles ahead of a wildfire’s front and that up to 60% of WUI home ignitions are from “red snow” (burning brands).
〉 A hazard assessment: The hazard assessment characterizes the likelihood of a vegetation fire within proximity of a structure.
〉 An exposure assessment: The exposure assessment characterizes the potential exposure of a structure to ignition sources should a vegetation fire occur in proximity.
Measures to Improve Structure Survivability
A structure’s survivability can be increased by implementing a number of improvements including:
〉 Materials used on the exterior of buildings should be noncombustible and fire resistant, including roof materials, external walls, trim, finishes, and exterior windows.
〉 Openings in the exterior walls should be protected against wildfire intrusion. This includes doors, windows, skylights, and vents (passive and active).
〉 An actively practiced vegetation monitoring and management program should be developed and implemented; including maintaining defensible spaces around the building, where vegetative areas and other ignitable fuels are removed or reduced to prevent or retard the spread of wildfire towards the building.
〉 Properly maintained fire department access routes should be available and reviewed by the local responding fire authority for acceptability.
〉 Combustible and flammable material stored outside and within proximity to the structure should be removed, including artifacts such as wooden or plastic pallets, fuel gas tanks such as LPG (liquified propane gas) and liquid fuel tanks.
〉 Depending upon the topographical features of the surrounding areas, firebreaks, fuel breaks, and setbacks should be used where applicable.
Minimizing Smoke Infiltration
Wildfires not only impact property but smoke infiltration can significantly impact employee well-being, resulting in eye, nose and throat irritation as well as coughing or wheezing, making breathing difficult. Preventing the infiltration of wildfire smoke and the use of indoor air filtrations are two principle strategies for mitigating indoor exposures to particulates and should include the following actions:
〉 Ensure any passive vents leading from the exterior of the building to the interior are covered, closed, and or sealed.
〉 Ensure exterior doors and windows are able to be fully closed, have tight seals and are able to be positively latched.
〉 Seal cracks or openings of exterior walls (e.g., with caulk).
〉 Set HVAC controls to full recirculation mode during a smoke event. Make-up air or outside air intake into the building, should be ceased or limited (to the extent possible) until the air quality is deemed acceptable.
We Are Here to Help
While the risks from wildfires cannot be completely prevented, having a comprehensive wildfire readiness plan, that includes employee fire preparedness and prevention training in addition to established evacuation routes, can help minimize damage to both property and keep employees safe.
