Potential Airborne Particulate Matter (PM) Exposures for Firefighters Working Outside Live-Fire Training Structures

Firefighting instructors and students may be exposed to fire effluent, including particulate matter (PM), during live-fire training. PM exposure risks may increase while preparing scenarios, staging materials and/or instructing/debriefing when respirators are often removed while operating outside of live-fire training structures. Exposure to large quantities of airborne PM has been recognized as harmful to human health. To protect instructors' and students' health, several control measures have been proposed, including incorporating different training fuels (substitution control), changing locations where instructors and students stage (administrative control) or wearing respiratory protection even when outdoors (PPE control). Stationary, time-resolved, optical real-time PM area air measurements were collected from outside two different live-fire training structures, including a single-story structure used for fire behavior training ("Fire Behavior Lab", incorporating 5 different training fuels) and a two-story structure made from concrete used for tactical training ("Multicompartment Live-Fire Training Structure", incorporating 3 different training fuels). In the Fire Behavior Lab, where fuels are mounted on the ceiling with limited ventilation (which can reduce air entrainment), fuel load had a limited impact on exterior PM concentrations, but location of the instructor (upwind from structure, moving farther away from structure) reduced the exposure hazard. For the Multicompartment Live-Fire Training Structure, different fuel loads had a more notable impact on training fire environments within the structure as well as PM concentrations outside the structure. In particular, high PM concentrations were found on the second floor, and in some situations, fire instructors may have limited ability to relocate when operating outside of elevated floors. In these cases, procedures may need to be implemented to provide reserve air supplies to these locations or rotate in new personnel to ensure proper respiratory protection for the duration of the training exercise.