The impact of forest fire smoke on building materials and electronic equipment
Forest fires can affect contain a variety of pollutants that affect wood, steel and concrete construction materials.
Forest fires are a natural phenomenon that occurs in many parts of the world. In recent years, however, forest fires have become more frequent and more severe due to climate change. Canadian forest fires are currently affecting states in the U.S. As of June 8 2023, cities including Washington, D.C., Philadelphia, New York, Baltimore, Buffalo, and Chicago, issued air quality alerts categorized as ‘Unhealthy’, due to the smoke. While the immediate effects of forest fires are devastating, the potential long-term impact can be equally severe.
Damage to buildings and electronic equipment is a significant concern after exposure to smoke. We will examine the effects of forest fire smoke on buildings and equipment, and share guidance to mitigate the risks.
Effects of forest fire smoke on building materials
Smoke from forest fires can contain different pollutants like carbon monoxide, volatile organic compounds (VOCs) and particulate matter. The particulate is especially concerning because it can attach to surfaces, accumulate over time, and lead to staining and discoloration of susceptible surfaces.
Wood members
Structural properties of wood members are not affected by smoke alone. Depth of char for members in close proximity to fire is a strong indicator of damage severity. Base wood dimensional properties can be measured beneath the char layer and residual structural properties can be determined. Metal connectors exposed to fire or high temperatures should be carefully inspected for deformations and loss of connectivity.
Structural steel members
Properties of structural steel members are not impacted by smoke alone either. Structural steel properties are affected by high temperatures. Structural steel begins to lose strength at temperatures of around 600°F and loses essentially all of its strength at around 2000°F.
Structural steel deformations after high-temperature exposure may be visible to the unaided eye during visual inspections. Using the fire investigation’s determination of fire temperature, initial “triage” decisions can be made as to which members can remain or need to be replaced before more detailed inspections can be performed.
Reinforced concrete members
Structural properties of reinforced concrete members are not affected by smoke alone. Reinforced concrete members have a relatively high tolerance for fire and high temperatures before structural damage. Reinforced concrete exposed to high temperatures will initially exhibit a red to pinkish color before turning a whitish gray and then a buff color if the temperature continues to increase.
“Sounding” of reinforced concrete members is a method of non-destructive testing to determine if internal delamination has occurred and consists of impacting the concrete with a tool and listening for dull or hollow sounds. Other non-destructive methods include ultrasonic pulse velocity testing that provides data for correlation to published values for concrete compressive strength to determine if the concrete has lost capacity due to fire.
Effects of forest fire smoke on electronic equipment
Smoke contamination poses a concern when particles from burning material settle on exposed electronic surfaces. Due to building ventilation systems and open points of ingress, smoke circulates to different areas. As a result, equipment throughout a building may be exposed to contaminants at varying levels. Additionally, because of ventilation fans and openings in equipment enclosures, smoke is introduced into equipment where it settles on sensitive electronic components and circuit boards.
There are two mechanisms by which smoke adversely affects equipment.
First, smoke consists of minuscule particles from combusted material. Smoke can cause damage to mechanical assemblies by acting as an abrasive between moving components.
In addition, the particles borne in smoke can clog filters, thereby obstructing airflow and causing equipment to overheat. Of greater concern is the effect of smoke when off-gassed materials are potentially corrosive. Corrosive particulate actively participates in the corrosion of susceptible assemblies.
Industrial hygiene
In order to efficiently evaluate potential impacts on the subject property, EFI Global’s industrial hygienists (IHs) utilize combustion byproducts (soot, char and ash) as indicators to evaluate potential exposure. Combustion byproducts (CBP) are the most common indicator associated with damage resulting from a fire and also provide a quantifiable metric to determine the extent of the impact. Additionally, combustion byproducts are typically less likely to dissipate in the absence of any cleaning activities and provide a more reliable indicator for potential impacts. However, when evaluating potential smoke exposure, alternate sources of combustion must be considered.
Background concentrations of CBP are commonly found on interior building surfaces, especially those that are infrequently cleaned (i.e., trusses, decking, ceiling fixtures, etc.), or where combustion particle-generating sources exist. Within a property, there can be localized CBP-generating sources that contribute to the background concentrations on interior surfaces. Typical background contributors involving interior property could include but are not limited to:
Outdoor environmental background infiltration through open doors or windows (e.g., vehicle exhaust), cooking processes, some appliances, fireplace operation, smoking, and candle or incense burning.
Depending on the facility type (e.g., commercial, manufacturing, residential), there are a variety of additional factors influencing background accumulation of CBP in a structure which can include: cleaning frequency, building designs, ventilation rates, operational activities, and presence of combustion equipment, appliances or vehicles.
For this reason, it is important to quantitatively evaluate surface concentrations of CBP on building materials to compare impacted and non-impacted surfaces to develop protocol recommendations, rather than evaluating impact utilizing a presence/absence method.
CBP particles transport through a structure similar to that of environmental dust, following air currents and settling on surfaces. Additionally, heated air from a fire can produce pressure differentials that create lift that promotes the migration of particulates higher in the structure before they settle or are ventilated. CBP particles have characteristic deposition or entrainment patterns that affect surfaces differently. CBP particles deposit more readily on large horizontal surfaces, metal, plastic, or where active air currents are present (i.e., heating, ventilation and air conditioning (HVAC) systems).
CBP particles also tend to deposit more readily at transition points between surfaces (wall to flooring, around electrical fixtures, structural surfaces, etc.), and on surfaces with a static electric charge. These patterns provide evidence of migration pathways for airborne contaminants and can be utilized to aid in the development of an appropriate sampling and assessment strategy. These patterns become more apparent depending on the severity of the combustion event and the amount of CBP particles released.
When responding to smoke claims, EFI Global engineers and industrial hygienists conduct visual non-invasive inspections to understand the severity of exposure/damage. Based on the results of the initial inspection, recommendations are conveyed which could include a more comprehensive inspection/investigation including non-destructive and/or destructive testing.
After the inspections and testing, the exposure and potential damage will be defined, and recommendations are communicated for cleaning, repair or replacement, as needed, to return the structure to its pre-loss condition.
The impact of forest fire smoke on building materials and electronic equipment can be significant — leading to potential electrical and structural problems. Electronic and electrical equipment like control panels and HVAC systems can experience system failures if left exposed, which can also lead to costly repairs or replacements.
Alexander Smith (alexander.Smith@efiglobal.com) is an environmental advisor; Peter Ricchio is associate vice president, service line; and Paul Gilbert is the director, client relations, and forensic equipment consultant for EFI Global. Reprinted with permission from EFI Global, a Sedgwick company.efiglobal.com
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