Physiological study into heat stress

    A group of firefighters wearing turnout gear completed a defined work/rest cycle in a controlled environment as their body core temperatures, heart rates, and skin temperatures were monitored. Over a period of several weeks, the same participants repeated the trial three times so they could wear each set of gear containing one of the three different protective barriers. And the results are exceptional:

    • The GORE® protective barriers delivered the highest breathability — significantly better than the competition.
    • All of the firefighters were able to complete the trial while wearing gear with GORE® protective barriers; on the contrary, 40 percent could not finish the test when wearing the competitive barrier because their heart rates exceeded their maximum, which were established as part of the safety criteria before the trial began.
    • RET results directly correlated with the participants’ physiological responses, whereas THL did not.

    Increase in Body Core Temperature

    U.S. military research has shown that once a body core temperature of 100°F is reached, each increase of only 0.1°F is physiologically significant, leading to an increased risk of heat exhaustion. At the end of the human trial, the average increase of body core temperature varied depending on the protective barrier in the gear. The GORE® PARALLON™ liner system performed the best, followed closely by the GORE® CROSSTECH® black moisture barrier; however, the increase with the competitive barrier was the largest. These results confirm that GORE® protective barriers are the most breathable.

    Body Core Temperature Response to Work/Rest Cycle

    Rest cycles are crucial to enable your body to recover from the strain of the challenging environments in which you work. When the participants were wearing the GORE® PARALLON™ liner system or GORE® CROSSTECH® black moisture barrier, the rest periods were more effective and they were able to complete the entire trial; when they wore the competitive barrier, their temperatures continued to rise rapidly. In fact, 40 percent of them were pulled out during the second work cycle because their heart rates exceeded their maximum rates, which were established before the trial began.

    RET (Resistance to Sweat Evaporation) versus THL (Total Heat Loss)

    Testing the performance of the materials in your gear can provide valuable information for gear selection. The THL test has done a great deal of good for the firefighter, helping to improve how well gear can shed excess body heat; but it evaluates performance in a relatively mild environment, similar to a conditioned office space. And, it has been found that THL does not provide very useful information about how gear performs, particularly in warm or sunny conditions. The RET test can provide some of this valuable insight, which could be important to you in your gear selection.

    Before the trial began, each turnout gear composite was measured for THL and RET. While THL did not predict the differences seen in the human trials, the RET testing did. In fact, the THL results, which are what is commonly available to fire departments today, indicated that there should be NO difference in performance between the gear tested in this study. However, the trial confirmed that there were significant differences—the Gore technologies were more breathable and had a lower burden on the firefighters, as demonstrated by lower core temperatures, lower skin temperatures, and lower heart rates.