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Identify and Quantify Smoke Hazards for Safe Reoccupation
Urban wildfires pose significant challenges not only during the blaze but also in their aftermath. For Industrial Hygiene Investigators, Insurance Loss Adjusters, and Consultants conducting structural monitoring, assessing and quantifying post-fire smoke hazards is crucial to determine the safety and habitability of affected structures. TSI offers tools to detect the hidden dangers of wildfire smoke inside homes and businesses, particularly after fires in the Wildland-Urban Interface (WUI). Our instruments help you assess aerosol and gas contamination so that spaces are safe to reoccupy.
Understanding the Wildland-Urban Interface (WUI)
The WUI is where homes and human development meet wildland vegetation — forests, grasslands, or brush. Fires in these areas are especially hazardous:
- They burn both natural and synthetic materials (homes, vehicles, EV batteries, plastics)
- They generate complex combustion products — far beyond what’s seen in typical biomass fires
- Structures that survive can still be dangerously contaminated
These combustion products can include particulate matter, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), heavy metals, and other toxicants. These contaminants can infiltrate structures, adhering to surfaces and penetrating porous materials, leading to prolonged off-gassing and potential health risks for occupants.
The Problem with Traditional Smoke Assessment
Most insurance-driven hazard assessments use “legacy” methods designed for forest fires. These include:
- Mass-based aerosol sampling – often returns "non-detect"
- Sorbent tube gas sampling – often returns "non-detect"
- Wipe sampling – often returns "non-detect"
Why do these methods fail?
They weren’t designed to detect the ultrafine particles and complex chemical compounds from synthetic materials common in urban structures. And because cleaning often happens before sampling, contamination may be missed entirely.
HVAC: The Hidden Contamination Highway
Smoke doesn’t just affect what you can see. HVAC systems act as highways that spread particles and gases into every room of a structure. Even if the system was off during the fire, particles can settle inside and off-gas for months or years. Porous materials (drywall, carpets, upholstery) also absorb and hold onto toxic particles, including secondary organic aerosols (SOAs).
A Better Way to Assess Smoke-Impacted Structures
TSI supports a new approach that leverages real-time count-based particle size measurement and gas detection before cleaning begins. This approach:
- Uses Condensation Particle Counters (CNC) and Optical Particle Counters (OPC) for real-time Ultrafine (UFP) / Fine / Coarse aerosol readings
- Compares indoor particle counts to outdoor baseline levels
- Helps identify the most heavily impacted rooms — often aligned with wind direction or HVAC influence
- Offers insights into ultrafine particles (UFPs) and fine particle size, which carry the highest health risk and have negligible mass concentration making them undetectable by mass-based sampling and analysis methods
The Hard Data You Need
The TSI P-Trak Ultrafine Particle Counter and AeroTrak Handheld Particle Counter Model 9306 bundle provides a powerful solution for professionals assessing post-fire urban wildfire smoke hazards in homes and commercial buildings. The P-Trak Ultrafine Particle Counter detects and tracks airborne ultrafine particles, helping investigators identify contamination sources, while the AeroTrak 9306 Handheld Particle Counter delivers precise measurement of particle concentrations across multiple size ranges. Together, these instruments enable Industrial Hygiene Investigators, Insurance Loss Adjusters, and Consultants to accurately quantify airborne contaminants, assess indoor air quality, and determine whether structures are safe for occupancy or require remediation.
Wildfire Bundled CPC/OPC Kit (P/N 803400) consists of:
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Download the Application Note
Application Note EXPMN-028 - New Approach to Urban Post-Wildfire Monitoring Hazard Assessment
Count-based aerosol/particle measurements, using TSI P-Trak™ Ultrafine Particle Counter and AeroTrak™ 9306 V2 Optical Particle Counter, when conducting urban post-wildfire hazard assessments in homes or business structures.
Guidance and Resources
- The Challenges of Post-Fire Assessments, Part 1 - An Interview with Dawn Bolstad-Johnson. In: AIHA Synergist Blog, March 11, 2025
- Professionals engaged in post-fire assessments can refer to resources such as the AIHA's forthcoming guidance from the Real-Time Detection Systems Committee, which addresses instrumentation, sampling, and analysis in post-fire scenarios.
- Additionally, the AIHA's Technical Guide for Wildfire Impact Assessments provides detailed methodologies for evaluating wildfire residues in indoor environments.