How hot does a firefighter get? Simulated smoke dive reveals core temperatures

The heat hits you like a ton of bricks. Maybe flames do too. Smoke is everywhere, it’s hard to see anything. But you have to go in. More than likely, you probably have to lift, pull or carry heavy objects.

High-intensity work in extreme heat puts high demands on a firefighter. The body is exposed to great stress that can affect their health.

Heavy protective clothing and equipment can contribute to high cardiovascular stress, and overheating is a risk.

Physical and mental impact

Increased body temperature negatively affects cognitive function, and we lose the ability to reason clearly. Physical responsiveness is also reduced. The risk of heat strain, and in the worst case, heat stroke, increases.

A study conducted at FRIC, Norway’s fire research and innovation center, addresses heat exposure in professional firefighters. The study is published in the journal Industrial Health.

“We have investigated the physiological response to a simulated smoke dive in extremely hot environments. We also looked at the subsequent recovery phase,” says SINTEF researcher Mariann Sandsund.

Nineteen professional male firefighters performed a 15-minute smoke dive in a two-story heat chamber with a temperature of 110 to 272°C, followed by a five-minute stair walk outside the heat chamber. The firefighters’ heart rate, skin and core body temperatures were recorded continuously during the experiment.

Increasingly higher body temperature

The firefighters swallowed a temperature pill that measured their core temperature continuously. Skin temperature was measured with temperature sensors attached to the skin.

“Measured exposure temperatures of well over 250°C showed the extreme temperatures that firefighters can be exposed to,” says Edvard Aamodt, a researcher at RISE Fire Research in Trondheim.

“We also know from studies in other countries that the temperature can be much higher for short periods when working on a live fire event. It’s important to be clear about this.”

Heat stress tests have now been introduced as annual mandatory exercises for firefighters. But these tests vary between countries and even within the same country. More knowledge is essential in order to ensure good health and safety for this professional group.

“Physiological data from actual firefighting activity or realistic training has been in short supply,” says Mariann Sandsund.

The combination of high metabolic heat production, protective clothing and equipment, and hot ambient temperature leads to non-compensable heat stress.

This means that “heat production exceeds the heat loss potential, leaving the body in a state of continuous heat gain,” she says.

Knowledge can contribute to increased safety

During a smoke dive, firefighters use compressed air cylinders that provide approximately 20 minutes of air, depending on the work being performed. Firefighting activity may be repeated several times after short recovery breaks to cool down, hydrate and change air cylinders.

The highest maximum core temperature measured for all the firefighters was 39.6°C, with a peak individual variation of 40.2°C. With such high temperatures, it takes a long time for the core temperature to return to normal.

These results show that firefighters may risk returning to activity with a higher body temperature for each successive smoke dive, which can lead to dangerously high temperature levels. Short breaks of 20 minutes are therefore not always long enough for the body temperature to return to normal.

The results of the study provide a better understanding of physiological responses, the effects of protective clothing, and the workload experienced by firefighters during training and operations at high temperatures.

“The study results can contribute to promoting health measures and improving safety by adjusting the work routines, such as cooling strategies, hydration and rest schedules,” says Sandsund.

The researchers also believe that increases in body temperature and heart rate must be considered during real fires, when repeated smoke dives are necessary.