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문제 정의
- This study was conducted to investigate physiological responses to safety helmets and to examine the effects of frozen gelled packs inside the helmets in a hot environment. To address these problems, human wear test was performed on four males participant.
제안 방법
- At this time, this study showed physiological strain when wearing safety helmet and the possibility of reducing heat stress through physiological and subjective measures by using frozen gelled packs. Considering the fact that the head takes up only 7~10% of the total body surfece area, it is interesting that head cooling improves physiological responses and thermal sensation.
- Based on a pilot test that evaluated a total of 6 items(2 items for safety helmets, 4 items for cooling vests), two items(frozen gelled pack A from S company, 140g and frozen gelled pack B from H company, 160g) that indicated lower surface temperatures than others were selected, evaluated and used for tests on the human use. Frozen gelled pack A and the frozen gelled pack B is sold on the market, for safety helmets and cooling vests, respectively.
- Subjects arrived at the laboratory and rested for 30minutes after changing into experimental clothing and receiving instruments. During trials, subjects repeated exercise periods(walk- ing, lOmin) and rest periods(sitting, 5min) for an hour. The walking speed was about 120 steps/min.
- To address these problems, human wear test was performed on four males participant. Experiments were conducted in a climatic chamber at WBGT 33±1℃, under four experiment conditions: NH(not wearing a safety helmet), HA (wearing a safety helmet with frozen gelled pack A), HB(wearing a safety helmet with frozen gelled pack B) and OH(wearing only safety helmet). The results are as follows:
- The aims of this present study were to investigate the physiological responses and load of wearing safety helmet and to examine the effects that frozen gelled packs have on alleviating heat stress when used inside safety helmets. To look into these issues, tests were performed on human users in a hot environment and results were reported.
- Subjects provided informed consent before participating in this protocol. Trials were conducted each day at the same hour in order to exclude the effects of circadian rhythms.
대상 데이터
- Four physically-active males(age 21 years, height 173cm, body mass 77.9±8.3kg, body surface area 1.9±0.1m2) participated in trials. Subjects provided informed consent before participating in this protocol.
- The subjects wore undershirts(90g), underpants (74g), long-sleeved shirts(245g), long pants(391g), socks(41g), work uniform vest(249g, 65% polyester, 35% cotton), safety shoes(l, 457g) and safety helmet (428g). All clothing was made of 100% cotton except for the work uniform vest.
- a hot environment. To address these problems, human wear test was performed on four males participant. Experiments were conducted in a climatic chamber at WBGT 33±1℃, under four experiment conditions: NH(not wearing a safety helmet), HA (wearing a safety helmet with frozen gelled pack A), HB(wearing a safety helmet with frozen gelled pack B) and OH(wearing only safety helmet).
데이터처리
- 0 package was used and the values are given as means士SD. The paired t-test was conducted to compare the differences between frozen gelled packs A and B. A repeated one-way analysis of vari- ance(ANOVA) and correlation analysis were used for the four experiment conditions.
이론/모형
- body and the head. Subjective workload votes was quantified using a perceived exertion of Borg(7- point scale, 0=very easy, 6=very, very hard).
성능/효과
- 1) When comparing NH with OH, physiological responses such as Tsk, Tr, heart rate and sweat rate were significantly higher and subjective sensation were less hot, more comfort in OH than in NH(p<.05). In particular, skin temperature increases in OH were high on the forehead, cheek, front neck and back neck area, affected by wearing safety helmet.
- 3) Both HA and HB were rated less hot and less uncomfortable than OH on the head. Subjective sensations during exercise and rest in hot environment were significantly correlated to the physiological responses.
후속연구
- Considering the fact that the head takes up only 7~10% of the total body surfece area, it is interesting that head cooling improves physiological responses and thermal sensation. However, further study is suggested for frozen gelled packs that are light in weight and better fitted for the head because it was difficult in this study to explain in Ml the shape and weight of the frozen gelled packs.
- Because the frozen gelled pack B is 20g heavier than the frozen gelled pack A, the physiological strain might be increased while working in a hot environment. However, future studies should consider the weight of the frozen gelled packs, which, in this study, could not be controlled due to the limited goods available in the market.
- This study is expected to help millions of workers who consider wearing safety helmets as uncomfortable and messy.
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