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5 ways firefighters can manage heat stress

Understanding the role of PPE and overall health in combating heat stress

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Current research shows that heat stress puts an extraordinary burden on a firefighter’s cardiovascular system, with the worst outcome being a sudden cardiac event (SCE) like a stroke or heart attack.


Every structural firefighter knows from experience that fire suppression operations are hot, exhausting and dangerous, and this is amplified when the ambient temperatures and humidity outside climb. But did you know that heat stress is more than just uncomfortable – it can kill you?

Conventional wisdom says that heat stress puts firefighters at greater risk of developing heat-related illness (e.g., heat cramps, heat exhaustion, heat stroke). However, current research is showing that heat stress also puts an extraordinary burden on a firefighter’s cardiovascular system, with the worst outcome being a sudden cardiac event (SCE) like a stroke or heart attack.

What happens when firefighters get hot

Denise Smith, Ph.D., is the principal investigator for the SMARTER Project (Science Medicine and Research & Technology for Emergency Responders) and she’s the director for the First Responder Health and Safety Laboratory on the campus of Skidmore College in Saratoga Springs, New York. Her research includes the paper “Effect of Heat Stress and Dehydration on Cardiovascular Function.

In that paper, Dr. Smith and her research team wrote: “Firefighters are exposed to numerous life-threatening dangers, including high temperatures, flames, smoke, hazardous chemicals, and unstable structures. Despite these dangers, the physiological strain, specifically cardiovascular strain, associated with firefighting poses the greatest threat to the life and health of a firefighter.”

Their studies led Smith and the SMARTER team to identify cardiovascular strain associated with firefighting as a major safety concern in large part because cardiovascular strain can: 1) lead to an SCE in vulnerable individuals with underlying cardiovascular disease and 2) lead to fatigue and impaired performance in all firefighters (See Figure 1 below).


Figure 1. Hyperthermia and dehydration – aka, the “terrible twins” of firefighter heat stress – can cause myriad physiological and behavioral problems for firefighters.

Image/Robert Avsec

Causative factors in firefighter heat stress

Smith’s research demonstrated that there are three factors that contribute to firefighter heat stress: ambient temperature, PPE and heavy work.


Figure 2. The research conducted by Smith and her associates identified these three common aspects of a firefighter’s work that contribute to firefighter heat stress.

Image/Robert Avsec

NFPA 1971: Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting provides the specifications manufacturers must meet for both thermal protective performance (TPP) and thermal heat loss (THL).

TPP is a measure of the garment’s thermal insulation capabilities (protect the firefighter from external heat); THL measures that same garment’s ability to release the heat generated by the firefighter inside the PPE (protect them from their own heat).

PPE manufacturers’ fabric designers and engineers have been creating more breathable PPE components that work better at dissipating the heat generated by the working firefighter inside the PPE while still protecting them from the external heat threat. They’ve also been working with new fabric technology and garment construction techniques to give a firefighter greater flexibility and agility while working in their gear. Because when your turnout gear is stiff or bulky (or both), it means your gear is working against you, not with you, and that means you’re generating more body heat that needs to be dissipated.

5 ways to be physiologically ready for the fireground

This brings us to you – the firefighter wearing the PPE. Here are five ways firefighters can be physiologically ready to wear their PPE on the fireground.

1. Get an annual physical exam by a physician: Obesity and diabetes are both on the rise in the general population, and firefighters are not immune. Be sure the physician conducting the exam is informed and educated about what a firefighter does, especially the physical demands of the job. Share a copy of FSTAR’s “A healthcare provider’s guide to firefighter physicals” with your physician.

2. Stay hydrated: Your body needs water to perform. This holds true during your off-duty time as well – the water you drink today has a big impact on what you do tomorrow. A simple rule of thumb: Your urine should always be clear. If it’s any shade of yellow, you’re not keeping your tank full.

3. Change your diet: Instead of revamping your entire diet, start with small, incremental changes. For example, make a change in your breakfast (switch bacon and eggs to whole grain cereal) one day a week. As you discover newer and healthier breakfast fare items, incorporate them into your schedule – a new dish every week. Before long, you’ll be eating a healthier breakfast seven days a week. Then move on to lunch.

The IAFF developed the Fit to Survive program and the National Volunteer Fire Council has the HeartHealthy Firefighter program, both of which are designed for firefighters looking to make improvements in both their on- and off-duty diet.

4. Get physically fit: Like making those dietary changes, if you are just getting started on improving your physical fitness, start small and build up. The key is to do something every day. You’re an occupational athlete, and your playing season is 24/7/365.

5. Get some sleep: A study published in the Journal of Clinical Sleep Medicine evaluated 7,000 firefighters from 66 fire departments for obstructive sleep disorder, insomnia, restless leg syndrome and shift work disorder. That study found that 37% of the study participants had one or more sleep disorders. The researchers found that compared with sound sleepers, those with a sleep disorder were about twice as likely to have a motor vehicle crash, to nod off while driving and to have cardiovascular disease or diabetes.

Get ready for the fireground

The structural firefighting PPE that helps protect you today is a marvel of engineering that’s designed from the ground up to protect you from the thermal and mechanical risks of structural firefighting. Equally marvelous is the ability of your PPE to move the moisture and heat that your body generates during firefighting away from you, helping you to avoid those negative consequences of heat stress. But don’t forget that it’s just as important for you, as the firefighter wearing the PPE, to do your part by being as physiologically ready for the fireground as possible.

Battalion Chief Robert Avsec (ret.) served with the Chesterfield (Virginia) Fire & EMS Department for 26 years. He was an instructor for fire, EMS and hazardous materials courses at the local, state and federal levels, which included more than 10 years with the National Fire Academy. Chief Avsec earned his bachelor’s degree from the University of Cincinnati and his master’s degree in executive fire service leadership from Grand Canyon University. He is a 2001 graduate of the National Fire Academy’s EFO Program. Beyond his writing for and, Avsec authors the blog Talking “Shop” 4 Fire & EMS and has published his first book, “Successful Transformational Change in a Fire and EMS Department: How a Focused Team Created a Revenue Recovery Program in Six Months – From Scratch.” Connect with Avsec on LinkedIn or via email.