Physiological Status Monitoring for Firefighters

Watching Out for Stress and Overexertion Before It’s Too Late

by Mark Mordecai

From the 2008 personal protective equipment e-Newsletter, sponsored by

Over the past decade, the number of firefighter on-duty deaths has remained persistently high (about 100) despite significant improvements in personal protective equipment. Providing better gear, although critically important, has had the unintended consequence of allowing firefighters to go deeper into buildings and for longer periods of time, which exposes them to even more risk.

To reduce firefighter fatalities, we have to look at the causes of on-duty deaths. The single largest cause, resulting in nearly half (45%) of all deaths, according to the U.S. Fire Administration ,1 is stress/overexertion. Physiological Status Monitoring (PSM) helps identify when a firefighter is in high-risk physiological stress before he becomes a fatality.

Firefighters face a unique set of risk factors associated with stress and overexertion. Among these as cited by a study conducted by the Orange County Fire Authority2 are as follows:

  • Sudden nervous system surges caused by unexpected alarms.

  • Rapid shifts from low to high levels of exertion.

  • Carrying, lifting, and wearing heavy protective gear and equipment.

  • Prolonged exposure to high temperatures.

  • Excessive fluid loss.

In firefighting, all of these risk factors are often present together. When you break down the risk to a firefighter of a fatal cardiovascular event by activity, according to the New England Journal of Medicine,3 you can readily see a pattern:

  • 32% during fire suppression.

  • 17% returning from an alarm.

  • 13% responding to an alarm.

  • 9% during nonfire emergencies.

  • 13% during physical training.

  • 15% during nonemergency duties.

Although responding to, working at, and returning from an emergency take up a relatively small portion of the total time a firefighter is on duty, they make up more than two-thirds of all on-duty fatalities. When you factor in the time spent in each activity, the odds of a fatal on-duty cardiac event are 10 to 100 times greater during fire suppression than nonemergency duty, two times greater than for police officers, and three times greater overall than for all workers.4 It’s no wonder that the International Association of Fire Fighters, the International Association of Fire Chiefs, and the National Volunteer Fire Council are all strong advocates for health, wellness, and fitness programs for firefighters.

In addition, The National Fire Service Research Agenda Symposium5 identified several aspects of firefighter health, wellness, and fitness issues as the highest priority for further research and action, including candidate selection and assessment, health maintenance, identifying risk factors for cardiovascular disease, physiological effects of heat stress and incident response, and functional capacity evaluation. Physiological Status Monitoring is a tool that can be used in all of these areas. Clearly, the fire service has recognized the problem and is aggressively looking for solutions.

A Globe advertisement from a 1908 issue of Fire and Water Engineering, the magazine which came to be known as Fire Engineering. Click to enlarge

An Innovative New Technology

Most active people today are aware of heart rate monitors used by runners and for fitness workouts. The object is to monitor your heart rate, allowing you to spend as much time as possible in a heart rate “zone,” which is typically a percentage of your maximum predicted heart rate based on age. These normally strap-based systems communicate through short-range signals to a watch-like device to monitor your workout. These systems are a rudimentary version of Physiological Status Monitoring, but they aren’t sufficient to meet the needs of the fire service.

A new and more technically advanced PSM system is now being developed by a team led by Globe and Foster-Miller for use by the military and the fire service. It embeds a built-in sensor system into a moisture-wicking and fire resistant T-shirt that would be worn in place of the current, cotton T-shirts that almost every firefighter wears today. These sensors measure heart rate, respiration rate, skin temperature, activity level, and posture. The data are collected and transmitted in real time as packets of information to a tiny receiver plugged into a laptop computer. If the system detects a potentially dangerous condition, it can alert the individual and the incident commander to pay attention before it’s too late. And it can record the data for post-activity analysis if the need arises.

Fire Service Applications

So how can the fire service use such a system? One way is as part of an individually tailored fitness workout program. An easy-to-use graphical user interface would show how you are doing, and the data could be logged to see how you are progressing toward your fitness goals, while providing training history and analysis. As with any fitness program, seeing progress is motivational.

Another use of the PSM system is in academy training. Providing real-time monitoring of each member of the team and a visual and audible alert to situations requiring attention could provide a critical early warning of potentially dangerous levels of stress and overexertion. By quantifying in a training environment just what the members of the team were experiencing during the session, individuals would have a better awareness of the importance of conditioning. And, as the need for training increases, the fire service can’t afford to lose anyone in training.

Hazmat operations and training are also well-suited for Physiological Status Monitoring. An encapsulated Level A suit is one of the most difficult protective ensembles in which to work, as the heat and moisture buildup puts more strain on your body. Feedback from hazmat personnel during PSM system testing indicates it is reassuring for personnel to know that someone is looking out for them, allowing them to focus on the job at hand. And current metrics for the amount of safe working time in hazmat operations are based on estimates of temperature, workload, and exposure. Monitoring the actual workload and vital signs may let personnel stay in longer to finish a job or warn them to come out sooner.

Of course, Physiological Status Monitoring holds the promise of helping to reduce fireground fatalities. During operations, the system can remotely alert the incident commander to situations that require attention. It can serve as an electronic backup to the current PASS device. And it can provide immediate vital data for rehab.


How do we know that the PSM system works? The first step is to compare the data in a laboratory setting between the data collected and transmitted by the T-shirt and a “Gold Standard” medical capnograph during a workout session both with full firefighting gear and without. This testing revealed an excellent correlation between the two sets of data (more than 90%) for both respiration rate and heart rate. Plotting these data points revealed that the T-shirt data was likely to be even more accurate than the capnograph, accounting for the most observable differential.6

As far as preliminary field testing, field trials have already been conducted during training exercises with the U.S. Army Special Ops and HazMat Ops and with the Santa Ana (CA) Fire Department for Level A HazMat Ops. These trials validated wearability as a base layer under issued gear and functionality of sensors, signal, and programming.

In the near future, there are plans to conduct more extensive operations field trials in the fire service for use in everyday firefighting duty with the Oxnard (CA) Fire Department and the Boston (MA) Fire Department. Many departments across North America have volunteered to conduct beta testing of these systems as we move forward.

More Research

Research is now focusing on using PSM in other ways. In one project, Worcester Polytechnic Institute (WPI), Foster-Miller, Globe, and the Worcester (MA) Fire Department are working to integrate firefighter location with Physiological Status Monitoring. The goal of this decidedly futuristic concept is to wirelessly locate, track, and monitor individual crew members throughout multi-story structures in real time using a laptop with an intuitive graphical interface. It’s an ambitious project, but it is already demonstrating exciting potential in firefighter location and validating the ability of using the PSM system as the platform for additional functionality as these technologies become commercially available.

Another soon-to-be-launched research project is looking at the physiological status of firefighters while on duty, studying the relationship of this status to the user’s fitness level and using the data to set appropriate physiological parameters for firefighters.

Are You Ready?

As with most new technology, the question is often asked whether the fire service is ready to adopt it. A survey taken during the IAFF Redmond Symposium in 2007 revealed that more than 85% of the health and safety audience was willing or very willing to wear a T-shirt incorporating PSM.7 A similar survey conducted at FDIC 2008 showed that more than 90% of this broader spectrum fire service audience was willing or very willing to wear a T-shirt incorporating PSM.8

We are on the cusp of understanding the root cause of firefighter on-duty deaths from stress and overexertion. We have a working new technology, Physiological Status Monitoring, which can provide a warning before it’s too late. This technology can be deployed as easily as replacing a common T-shirt with a technically advanced T-shirt that incorporates unobtrusive sensors and a miniaturized transmitter. The system including the T-shirt, sensors, transmitter, signal, receiver, and programming is being developed for military and firefighting applications. Ongoing research and testing will provide important data about the physiological status of firefighters performing the range of actual fire service duties. And the fire service is willing to wear it.

No one expects that deploying this new technology will prevent all on-duty firefighter fatalities or disabilities from stress and overexertion, but think of how important it would be to the affected individuals, their families, and their departments to identify even a few before it was too late.


1. U.S. Department of Homeland Security (DHS), Federal Emergency Management Agency (FEMA), U.S. Fire Administration, Firefighter Fatalities in the United States in 2006, July 2007.
2. Nancy Espinoza and Michael Contreras, Orange County Fire Authority, Safety and Performance Implications of Hydration, Core Body Temperature, and Post-Incident Rehabilitation, Final Report December 2007.
3. Stefano N. Kales, Elpidoforos S. Soteriades, Costas A. Christophi, and David C. Christiani, “Emergency Duties and Deaths from Heart Disease among Firefighters in the United States,” New England Journal of Medicine, March 22, 2007.
4. Ibid.
5. National Fallen Firefighters Foundation, Report of the National Fire Service Research Agenda Symposium, June 1-3, 2005.
6. Jim Duckworth, Worcester Polytechnic Institute, Integrated Firefighter Location and Physiological Monitor, Presentation to the Worcester County Fire Chiefs Meeting, April 17, 2008.
7. Globe Manufacturing Company, Fire Service Survey: Physiological Status Monitoring, Redmond Symposium, October 2007.
8. Globe Manufacturing Company, Fire Service Survey: Physiological Monitoring, Fire Department Instructors Conference, April 2008.

Mark Mordecai is director of business development for Globe Manufacturing Company, where he is responsible for driving product development and marketing. Globe, manufacturer of NFPA-compliant firefighter suits, produces a range of premium performance personal protective equipment for fire, rescue, emergency medical, and other first responders.

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