Caravello Victor, McCullough Elizabeth A, Ashley Candi D, Bernard Thomas E
College of Public Health, University of South Florida, Tampa, FL 33612-3805, USA.
Eur J Appl Physiol. 2008 Sep;104(2):361-7. doi: 10.1007/s00421-007-0655-9. Epub 2008 Jan 3.
A limiting factor for clothing ensembles inherent during heat stress exposures is the evaporative resistance, which can be used to compare candidate ensembles and in rational models of heat exchange. In this study, the apparent total evaporative resistance of five clothing ensembles (cotton work clothes, cotton coveralls, and coveralls made of Tyvek 1424 and 1427, NexGen and Tychem QC was estimated empirically from wear trials using a progressive heat stress protocol and from clothing insulation adjustments based on ISO 9920 (2007) and wetness. The metabolic rate was moderate at 165 W m(-2) and relative humidity was held at 50%. Twenty-nine heat-acclimated participants (20 men and 9 women) completed trials for all clothing ensembles. A general linear mixed effects model (ensemble and participants as a random effect) was used to analyze the data. Significant differences (p < 0.0001) among ensembles were observed for apparent total evaporative resistance. As expected, Tychem QC had the highest apparent total evaporative resistance at 0.033 kPa m(2) W(-1). NexGen was next at 0.017 kPa m(2) W(-1). These were followed by Tyvek 1424 at 0.015 kPa m(2) W(-1), and Tyvek 1427, Cotton Coveralls and Work Clothes all at 0.013 kPa m(2) W(-1). This wear test method improves on past methods using the progressive protocol to determine evaporative resistance by including the effects of movement, air motion and wetness on the estimate of clothing insulation. The pattern of evaporative resistance is the same as that for critical WBGTs and a linear relationship between apparent total evaporative resistance and WBGT clothing adjustment factor is suggested. With the large sample size, a good estimate of sample variance associated with progressive method can be made, where the standard error is 0.0044 kPa m(2) W(-1) with a 95% confidence interval of 0.0040-0.0050 kPa m(2) W(-1).
热应激暴露期间服装组合固有的一个限制因素是蒸发阻力，它可用于比较候选服装组合，并用于热交换的合理模型。在本研究中，通过使用渐进热应激方案的穿着试验以及基于ISO 9920（2007）和湿度的服装隔热调整，对五种服装组合（棉质工作服、棉质工作服连体裤以及由特卫强1424、1427、NexGen和泰科姆QC制成的工作服连体裤）的表观总蒸发阻力进行了实证估计。代谢率为适中的165 W m(-2)，相对湿度保持在50%。29名热适应参与者（20名男性和9名女性）完成了所有服装组合的试验。使用一般线性混合效应模型（将服装组合和参与者作为随机效应）分析数据。观察到服装组合之间在表观总蒸发阻力方面存在显著差异（p < 0.0001）。正如预期的那样，泰科姆QC的表观总蒸发阻力最高，为0.033 kPa m(2) W(-1)。其次是NexGen，为0.017 kPa m(2) W(-1)。接下来是特卫强1424，为0.015 kPa m(2) W(-1)，特卫强1427、棉质工作服连体裤和工作服均为0.013 kPa m(2) W(-1)。这种穿着测试方法在过去使用渐进方案确定蒸发阻力的方法基础上有所改进，它纳入了运动、空气流动和湿度对服装隔热估计的影响。蒸发阻力模式与临界湿球黑球温度（WBGT）的模式相同，并且表观总蒸发阻力与WBGT服装调整因子之间存在线性关系。由于样本量较大，可以对与渐进方法相关的样本方差进行良好估计，其中标准误差为0.0044 kPa m(2) W(-1)，95%置信区间为0.0040 - 0.0050 kPa m(2) W(-1)。
