Clearing the Air: What Do You Get For “30 Minutes”?

By Gavin Horn

Critical decisions based on “air” are made on the fireground and training ground and in the boardroom. How much air is still available? How much air has been consumed? How do we train firefighters to be critically aware of their air? How much air do we need to provide to keep our members safe? While standards that might shift thoughts on these questions are changing, there is also very recent Department of Homeland Security (DHS) Fire Prevention and Safety- funded research that is shedding new light.

The Rule of Air Management Q & A 

SCBA: The Air Management Conundrum

Is Your Department Complying with the NFPA 1404 Air Management Policy?

This article discusses the effects of working in self-contained breathing apparatus (SCBA) on the human body in terms of heat stress, impact on injury risk and a firefighter’s ability to do the job on the fireground. You will see new data on how a firefighter’s physical abilities change with the second air cylinder and how this can be related to a firefighter’s preparation for the job and learn about tradeoffs between 30-minute and 60-minute air bottles as well as how these large cylinders may affect work/rest cycles and subsequent risk.


Firefighting results in roughly 35,000 TO 40,000 fireground injuries each year; the two leading categories are slips, trips and falls (22%) and overexertion/strain (23%). Despite the high rate and cost of slips, trips and fall events, there has been relatively little scientific study on the effects of firefighting activities while wearing structural firefighting personal protective equipment (PPE) on the ability to move safely on the fireground. Thus, evaluating the effect of SCBA size and potential novel designs on safety of movement is important for firefighter health and cost containment.

The increased movement restriction caused by firefighting SCBA is also likely to be a significant contributor to overexertion/strain injuries in part as a result of increased metabolic stress.  The bulk of overexertion/strain injuries on the fireground are attributed to handling a hoseline and overhaul operations, both of which require significant upper-body movement that can be restricted by SCBA weight and design.  These operations require moving a moderate amount of weight for a relatively long time, which increases metabolic stress and may lead to fatigue-related injuries. Furthermore, heat stress is known to hasten the onset of muscular fatigue, cause dehydration, increase cardiovascular strain, and interfere with cognitive function. These factors all contribute to overexertion/strain that can affect movement biomechanics and reduce an individual’s ability to maintain situational awareness of the surrounding physical space. As such, it is also necessary to understand how metabolic stress caused by strenuous firefighting activity interacts with SCBA design to affect safety of movement.

There has recently been a significant increase in the purchase and use of extended duration (>30 minutes) air cylinders in the fire service. This additional air volume from extended duration air cylinders will impact the available work time prior to exiting the structure.  At the same time, it has been found that nearly all of the physiological strain caused by firefighting SCBA can be attributed to weight and that heavier SCBA bottles can significantly impact firefighter performance even in the absence of fatigue.  The understanding of the combined impact of firefighting activity and SCBA design on firefighter safety of movement and development of metabolic stress is not well-developed.

At the Illinois Fire Service Institute (IFSI), we have recently conducted a study to learn more about each of these concerns.  This new information fills an important void and advances our understanding of the effect of SCBA design on safety of movement on the fireground.

IFSI’s Study


Thirty firefighters from across the state of Illinois participated in a DHS-funded study “Effect of SCBA Design & Firefighting-Induced Fatigue on Balance, Gait, and Safety of Movement” at the IFSI. During this study, firefighters were asked to conduct a series of activities that simulated common fireground activities, including (1) a stair climb, (2) a simulated hose advance, (3) a simulated search, and (4) a simulated overhaul task.  These activities were completed in full National Fire Protection Association 1971, Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting, compliant PPE in a heated room using a test station that was validated as a reliable substitute for live-fire training activities in the IFSI burn tower.  All activities were performed at a self-selected pace that simulated the effort a firefighter would use on the fireground. Firefighters were allowed to modify their technique or to rest at any time throughout the activity.  Firefighters completed the simulated firefighting activity wearing either traditional, single-cylinder carbon fiber SCBA  with durations rated for 30, 45, and 60 minutes (at 4,500 pounds per square inch pressure) or  a prototype low-profile 45-minute SCBA. The first series of these scenarios required firefighters to work through one bout of each of the four activities only once on a two-minute work-rest cycle. Three additional trials were then completed with firefighters wearing the (1) 30-minute SCBA and completing two bouts of activity with a five-minute rest in between bouts,( 2) 60-minute SCBA with two bouts of activity and rest in between bouts, and (3) 60-minute SCBA with two bouts of activity back to back.


Immediately before and after the simulated firefighting activities, participants passed through a biomechanics assessment obstacle course two times at “fireground pace.” The course was designed to simulate movements/obstacles commonly encountered on the fireground including:

·        Crossing over an obstacle on the ground (e.g., large-diameter hoseline).

·        Walking up and down steps.

·        Free walking on flat ground.

·        Passing through a fixed wall opening based on standard building practices (studs placed at 16-inches on-center).

·        Completing a functional balance task to assess firefighter’s body control and functional balance while encountering obstacles, applicable to fireground conditions.

Throughout the obstacle course, firefighters’ boots were tracked using three-dimensional motion capture cameras so that the research staff could determine the exact location of the firefighter and characterize changes in balance, walking abilities, and obstacle crossing using well-established and reliable tools. Further, time to complete each task and any errors committed at each station were recorded.

Heart rate and core body temperature were continuously measured throughout all data collection sessions.

Overview of Results

In this study, we found the following:

1.      Reduction in a few measures of safety of movement (reduced obstacle and stair-crossing clearances, reductions in functional balance abilities) after a single bout of firefighting activity.

2.      Much larger and more significant reductions in safety of movement after two bouts of firefighting activity.  Firefighters’ heart rates and core temperatures were significantly higher; they felt much worse, and changes in biomechanics that might suggest increased risk for slips, trips, and falls were characterized.

3.      After a single bout of firefighting activity, a few small differences were noted between the safety of movement when wearing a 30-minute vs. a 60-minute SCBA. These differences were not nearly as large as those found pre- to post-firefighting.

4.      When comparing a traditional SCBA to a prototype, low-profile unit of similar weight, relatively small differences were detected.

5.      Roughly 1/3 of the firefighters who participated in this study were unable to complete at least one of the two bout scenarios.  On average, these firefighters were significantly less fit and were larger than the group that was able to complete all of the scenarios.


The data collection and analysis for this study has recently been completed, but the discussion with the fire service as to the impacts of this information is underway. It began at FDIC 2015. Laboratory data are important to collect to provide controlled understanding of effects of designs, but it is critical that we work to integrate this knowledge into the existing decision-making process on all levels of the fire department to reduce risks for injuries and fatalities in the fire service.


Gavin Horn has served as the IFSI director of research since August 2004, immediately after receiving his PhD in mechanical engineering from the University of Illinois at Urbana-Champaign. His research interests lie in the areas of first responder technology development, firefighter health and safety research, material testing and design, infrared imaging, and nondestructive evaluation. He holds a senior research scientist position with the Advanced Materials Testing & Evaluation Laboratory at Illinois. He has published 35 peer-reviewed journal articles and has given more than 50 presentations at professional conferences around the world. He serves as a volunteer firefighter/engineer with the Savoy (IL) Fire Department, where he was named the 2011 Firefighter of the Year.


No posts to display