Heat stress takes on new meaning for firefighters in the summer

By Laurelle Walsh

When summer heat arrives and temperatures hit the high 90s for days on end, most people in the Methow choose to limit their activities to early morning and spend their afternoons indoors.

But when a structure fire erupts, or the hills explode in flames, firefighters spring into action, exerting themselves for long hours in extreme heat and under the fiercest conditions.

How do firefighters do strenuous work outdoors in temperatures that cause the rest of us to wilt? How are they able to crawl into burning buildings hauling heavy hoses, dressed in bulky bunker gear that does not breathe?

Acclimation, training, and a strict program of rehabilitation are part of the answer; but adrenaline, physical fitness and sheer will power also come into play, according to Okanogan County Fire District 6 officials.

“New firefighters have to learn to pace themselves,” said Winthrop Captain John Owen. “We get trainees to recognize heat and its effects, and to recognize what’s going on with their buddies.

“You have to know your own self,” Owen continued. “I always tell my buddy that I dehydrate easily.”

Heat stress

Firefighting tasks require a tremendous amount of energy and, as the human body burns fuel, it produces its own heat. In fact, even after you stop working, your core temperature continues to rise for a time, according to Owen. Add to that high ambient temperatures and fire, and heat stress becomes a problem.

Heat stress reduces mental performance, and slows reaction time and decision time, according to the International Association of Fire Fighters (IAFF). Under heat stress, routine tasks are done more slowly and errors are more common. In addition, dehydration greater than 2 percent of body weight adversely affects mental function during simple tasks.

In fact, proper hydration is the most critical factor in the prevention of heat injury, according to the IAFF.

Thirst cannot always be relied upon to stimulate drinking, so cool water must be readily available and drinking must be encouraged. “We teach our guys to stay hydrated,” Owen said.

As anyone who has experienced the transition from spring into summer knows, the human body can get used to hot temperatures.

Firefighters actively train to acclimate to heat. “You can acclimate to heat, but it takes time,” said Owen. “On days like today [pushing 100 degrees] I go for a walk in the heat. A person in reasonable shape can acclimate in five to 10 days,” he said.

The heat inside a burning building is basically the same any time of year — up to 2,000 degrees Fahrenheit, according to District 6 Chief Don Waller. The difference is in summer firefighters may be hot before they even don their gear. With summer temperatures in the 90s, firefighters heat up faster and can’t cool down as quickly, Waller said.

Into the fire

The body naturally cools itself by sweating. As sweat evaporates from the skin, it lowers body temperature. But when a body is encapsulated in protective clothing and self-contained breathing apparatus — SCBA — the sweat/evaporation cycle is effectively eliminated, and body temperature begins to rise.

Structure-fire gear — also called personal protective equipment, or PPE — weighs about 60 pounds. PPE includes boots, helmet, gloves, coat, pants and a form-fitting hood that covers every inch of skin except for what’s covered by the sealed SCBA face mask. The clothing is constructed of separate layers that wick moisture, provides a thermal barrier, and has a flame-retardant exterior.

“When you put on PPE, you’re in that cocoon the whole time,” said Owen. “It’s designed to keep the heat out, but it also keeps it in. As soon as you put this on, you’re almost shutting down the body’s ability to cool itself.”

In training — ongoing for all District 6 firefighters — and during fire calls, commanders emphasize division of labor and break down tasks so that no one person takes the full load, Owen said.

A structure-fire team is made up of two people working the hose inside the building, and two firefighters outside providing backup, according to Waller. Ideally, he said, two or three teams work on a fire at once. In order to rotate tired people into less-strenuous positions or into rehab, an adequate roster of volunteers needs to be available to answer fire calls, Waller said.

A firefighter goes into rehab as soon as his SCBA air tank is used up, usually in 20 to 30 minutes, Waller said. A rehab tarp is set up in the shade, away from the smoke environment, where Aero Methow EMTs stand by and monitor firefighters’ heart rates, body temperature and blood pressure. To cool down, firefighters remove their coats and hoods, and drink cool water or Gatorade to replenish fluids and electrolytes lost by sweating. Firefighters may also cool themselves in the cab of a fire truck or ambulance with the windows up and the air conditioning on.

After rehab, a firefighter may put on a new air bottle and go back into the structure; however, he or she is unlikely to go back in for a third time, Waller said. “It’s up to the incident commander to determine, and it depends a lot on the physical fitness of the firefighter. You can look at them and see when they’ve had too much,” he said. “In a large fire you go through people pretty fast.”

Cumulative effects

After a week of nonstop structure protection during last summer’s Carlton Complex Fire, the cumulative effects of heat and fatigue on firefighters became apparent to District 6 commanders.

“We had to be conscious of all aspects of the firefighters’ health and well being,” said Owen. “We still followed the rules of rehab, and we tried to give our firefighters 8 hours off every day.”

Heat is somewhat less of a danger in wildland firefighting, according to Owen, in part because wildland PPE weighs less and breathes better than the gear worn in structure fires. It may also be possible to pace yourself better when you’re not fighting a fire in an enclosed space, he added.

On the other hand, wildland firefighters may not be able to retreat to a cool place during periods of rest, and heat stress is cumulative, Owen noted.

During the Carlton Complex, Owen’s team did an “after action review” each day to share experiences and suggestions and make adjustments based on what they were seeing on the fire scene, Owen said. “It gave each team member much needed decompression time — sharing experiences, more or less relaxing, dealing with the emotional aspect of what was happening to our valley, friends, and family,” he said. “We all still talk about last summer, get ready for this summer, and anticipate our next response.”