Effect of Ice Slurry on Suppression and Cooling of Body Temperature in Firefighters

Firefighters often work in harsh high-temperature and high-humidity environments such as scene of fires. Additionally, the heat and perspiration generated by the human bodies further increase the temperature and humidity inside the fire-protective clothing. The aim of this research is to scientifically evaluate the body load based on vital data from firefighters according to the activities and environment of each firefighter and to further investigate the effect of cooling the human body by fluid intake with the aim of lowering the risk of heatstroke. In a series of experiments, six firefighters took exercise in an environment of 25 and 40 °C as a normal-temperature and a high-temperature condition, respectively. And they took in water or ice slurry before and after exercise. As the experimental result, in case of exercise in the high-temperature environment, intake of ice slurry caused rectal temperature to decrease rapidly compared with intake of water. But in the normal temperature, the cooling effect of rectal temperature by intake of ice slurry showed little difference from ingestion of water. The ear temperature did not show the difference by intake of water and ice slurry both; in addition, after the exercise 1, during rest time with intake of water, the ear temperature decreased to initial temperature at the normal-temperature and high-temperature environment. The trends of cardiac rate looked almost identical between intake of water and ice slurry in each environment for exercise, but after only the exercise 1, intake of ice slurry could decrease cardiac rate to initial condition earlier than intake of water. As a result of this research, ingestion of ice slurry was shown to be effective at reducing the rectal and body surface temperatures during rest after exercise in the high-temperature environment and slowing the heart rate during rest after exercise in both the normal- and the high-temperature environments.