Exposure Risks in Multi-Compartment Training Structure

New Peer-Reviewed Journal Article Characterizes Exposure Risks in a Multi-Compartment Training Structure

April 25, 2024

A new peer-reviewed journal article on thermal and chemical exposure risks in multi-compartment training structures has been published in Fire Technology. The paper builds on two previous publications that focused on a Fire Behavior Lab training structure and are part of the Training Fire Exposures from the Source: Developing a Risk-Benefit Framework research project.

While NFPA 1403-compliant live fire training is essential to prepare firefighters for emergency responses, this training can present thermal and chemical exposure risks to both instructors and students. To reduce these risks, training academies, fire departments, instructors, and standards-setting technical committees need more information on how different training fuels used in different orientations and amounts in common training structures can impact the environment in which firefighter training occurs. 

Characterizing exposure risks

The research team set out to better understand these exposure risks. They tested three wood-based materials commonly used as training fuels (i.e., low-density wood fiberboard, oriented strand board (OSB), and wood pallets) in a three story, multi-compartment concrete structure used for live fire training, with five replicates of each fuel. Throughout the experiments, the team measured heat flux, air temperature, and airborne concentrations of several contaminants—including known, probable, or possible carcinogens—at instructor locations. They also conducted additional exploratory tests, including one with an OSB-fueled fire with increased ventilation and another with smoldering straw-filled smoke barrels as an alternate means of reducing visibility.

The key findings include:

  • For nearly all compounds measured in this study, airborne concentrations were 10-100 times lower in the multi-compartment structure with fuels loaded on a ground-based burn rack than in the smaller, single compartment Fire Behavior Lab with fuels loaded high on the walls and ceiling.
  • OSB-fueled fires and fiberboard-fuel fires produced the highest median concentrations of total polycyclic aromatic hydrocarbons (PAHs) in the multi compartment training structure, while the pallet fuel package produced the lowest median concentrations of these compounds.
    • These trends generally followed the qualitative visual obscuration created by each fuel.
    • This result was in contrast to our related study in the Fire Behavior Lab where the pallet scenarios resulted in median total PAH concentrations that were higher than fiberboard or OSB scenarios.
  • Increasing the ventilation in the OSB experiment resulted in the highest temperatures in the fire room, but the lowest impact on visibility throughout the structure and the lowest overall concentrations of contaminants in this study. 
  • In contrast, the smoldering smoke barrel created a highly obscured environment and some of the highest concentrations of the targeted contaminants of any test, with minimal impact on thermal environment. 
  • Regardless of the wood-based product used, the temperatures and heat fluxes at the instructor locations on the first floor were considerably higher than those on the second floor. On the other hand, total concentrations of PAHs and total calculated toxic equivalents were similar on the first and second floors.

When combining the results presented in this paper with the earlier work in the Fire Behavior Lab, the instructor can further understand how the training fire environment is affected by many factors, including fuel material, fuel orientation, training structure size, ventilation, and the activities conducted.

While the live fire instructors have long understood that the more heat there is, the higher the potential thermal risk, this study also helps instructors to recognize that the more smoke there is, the higher the potential chemical exposure hazard. In addition, a training environment with lower temperatures does not necessarily equate to a lower chemical exposure risk.

“Throughout this study, we consistently found that decreasing visibility in live fire training was associated with increasing concentration of airborne contaminants that we were measuring. This finding clearly underscores the need for live fire training participants and instructors to consistently use respiratory protection when working in and around smoke and thoroughly clean their personal protective equipment and skin after the fire, regardless of the fuel package used.”
- Gavin Horn, Director of Research, FSRI

Instructors can take action to reduce exposure risks

Instructors are regularly faced with the dual challenge of creating a realistic training environment and reducing firefighters’ exposure risks. This manuscript, in conjunction with previously reported project results, supports instructors in balancing obscuration for training with potential exposure to thermal stressors and contaminants. 

Instructors may consider implementing the following control measures to reduce exposure risks while training in a multi-compartment structure: 

  • Increasing the instructors’ distance from the source fire whenever possible, 
  • Staying low and out of flow paths as feasible,  
  • And maintaining good hygiene and cleaning practices after live fire training.

Read the article

Collaborators for the manuscript include Kenny Fent from the National Institute for Occupational Safety & Health and Summer Neuman from UL Solutions, Asset and Sustainability Performance. This study was also supported by technical panel members from 18 organizations around the U.S. and by the Department of Homeland Security Fire Prevention and Safety Grant EMW-2019-FP-00770.

Training Fire Exposures From The Source: Developing a Risk-Benefit Framework