Alleviation of Heat Strain by Cooling Different Body Areas during Red Pepper Harvest Work at WBGT 33

Department of Clothing & Textiles, College of Human Ecology, Seoul National University, Korea.
Industrial Health (Impact Factor: 1.12). 01/2009; 46(6):620-8. DOI: 10.2486/indhealth.46.620
Source: PubMed


The purpose of the present study was to examine the effects of different types of personal cooling equipments (PCE) on the alleviation of heat strain during red pepper harvest simulated in a climatic chamber. The experiment consisted of eight conditions: 1) Control, 2) Neck cooling scarf A with a cooling area of 68 cm2, 3) Neck cooling scarf B (cooling area 154 cm2), 4) Brimmed hat with a frozen gel pack, 5) Cooling vest (cooling area 606 cm2), 6) Hat+Neck Scarf B, 7) Hat+Vest, and 8) Hat+Neck Scarf B+Vest. Twelve subjects worked a red pepper harvest simulated in a climatic chamber of WBGT 33 degrees C. The result showed that rectal temperature (T(re)) was effectively maintained under 38 degrees C by wearing PCE. Mean skin temperature (T(sk)) and heart rate (HR) became more stable through wearing PCE. When wearing the 'Hat+Scarf B+Vest', particularly, T(sk) and HR quickly decreased to the comfort level during the mid-rest stage. We confirmed that the vest with a cooling area of only 3.3% body surface area (BSA) was effective in alleviating heat strain in a simulated harvest work. Furthermore, the heat strain of farm workers can be considerably eliminated by the combination of the cooling vest, a scarf, and a brimmed hat, with the total cooling area of 4.2% BSA.

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    • "All rights reserved. Cadarette et al., 2006; Chou et al., 2008; House et al., 2013; Gao et al., 2011; Kenny et al., 2011), athletes performing sports activities or exercises (Purvis and Cable, 2000; Tate et al., 2008; Barwood et al., 2009a; Brade et al., 2010), and people doing office or other physical work (Choi et al., 2008; Gao et al., 2012; Nishihara et al., 2002). The cooling efficiency of PCM incorporated clothing has been widely studied by using thermal manikins, human trials and physiological models (ASTM F2371; Bogerd et al., 2010). "
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    ABSTRACT: Introduction: Heat stress has been considered as a common risk to impair work performance, which may lead to heat illnesses, work incidents, or even fatality. Over the past few decades, various types of personal cooling systems (PCSs) have been developed to mitigate heat strain, e.g., cooling vests with ice packs or phase change material (PCM) packs or frozen gel strips, garments with liquid cooling systems and garments with forced air ventilation. In this study, a novel personal cooling system (PCS) incorporated with both PCMs and ventilation fans was developed and its cooling efficiency was evaluated on a sweating manikin. Methods: A novel hybrid portable PCS incorporated with PCMs and ventilation fans was developed, which consisted of a long sleeve jacket and a pair of long pants. Four fans were embedded at the lower back and the lateral pelvis regions of the PCS. Twenty-four PCM packs (Gao et al., 2012) were also incorporated into the PCS. Six PCM packs were located at the chest region, 8 packs at the back region, 4 packs at the upper arm regions and 6 packs at the front thigh regions. A polyester T-shirt and briefs were worn under the PCS. A Newton type 34-zone sweating thermal manikin was used. A constant surface temperature of 34.0 °C was used to evaluate the cooling effect of PCS in the so-called isothermal condition (Tmanikin = Ta = Tr). The sweating rate was set at 1200 Four test scenarios were chosen: fans off with no PCMs (Fan-off, i.e., CONTROL), fans on with no PCMs (Fan-on), fans off with fully solidified PCMs (PCM+Fan-off ), and fans on with fully solidified PCMs (PCM+Fan-on). Two hot environments were selected: hot humid (HH) and hot dry (HD). The relative humidity (RH) of the HH and HD conditions was 75% and 28%, respectively, and the mean (SD) air velocity was 0.4 (0.1) m.s-1. Results and Discussion: Table 1 shows the heat loss and the cooling time of the PCS under different scenarios. In both conditions, the heat loss of Fan-on was higher than that of Fan-off. The PCMs led to a higher manikin heat loss at the initial testing stage and it gradually decreases to a steady state. There was no significant heat loss difference between PCM+Fan-on and Fan-on when the PCMs were fully melted. Similarly, no heat loss difference was found between PCM+Fan-off and Fan-off. The PCM+Fan-on and Fan-on exhibited a higher cooling power than PCM+Fan-off. The PCMs provided about 90~110 min and 20~30 min cooling duration in HH and HD conditions, respectively. Conclusion: The results demonstrated that the portable PCS developed could be able to provide effective heat removal from a sweating manikin in two hot environments with differing humidity levels, with fan cooling being much more effective with a lower rh, and more. The PCMs applied in the PCS provide effective cooling at the initial stage; as the manikin skin surface gradually gets wet, ventilation fans start to provide evaporative cooling .
    The 16th International Conference on Environmental Ergonomics (ICEE), Portsmouth, UK; 06/2015
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    • "However, the alleviation of torso and mean skin temperature increase did not lead to a significant lower core temperature and subjective thermal sensation , as reported in other studies in moderately hot environments (e.g. Choi et al. 2008). This is probably due to the fact that the more severe heat stress, clothing and equipment carried, and physical work in this study resulted almost in exhaustion when subjects stopped the heat exposure . "
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    ABSTRACT: A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated.
    Arbeitsphysiologie 12/2010; 111(6):1207-16. DOI:10.1007/s00421-010-1748-4 · 2.19 Impact Factor
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    • "There are also pre-cooling effects on the torso as shown in Fig. 1 in the preparation period (about 5-10 minutes), which can be clearly seen when comparing with baseline level at 20 °C. Frozen gel vests (807 g) have shown to reduce abdomen skin temperature to 1 °C during two hours simulated red pepper harvest work at WBGT 33 °C and relative humidity 65% (Choi et al 2008). However, it is surprising to notice that the study by Carter et al (2007) did not show significant alleviations of core, mean skin, and local scapular skin temperature using similar PCM vests during and at the end of simulated fire fighting, although there was a trend of local temperature reduction, which might be explained by the fact that, in this study, the heat stress was higher, the total exposure time was longer and skin temperature rise was greater at the end of heat exposure. "
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