Shin-ichi Sawada

Correction of the evaporative resistance of clothing by the temperature of skin fabric on a sweating and walking thermal manikin

Determining the evaporative resistance of clothing by using a sweating thermal manikin requires the accurate skin temperature of the manikin. The skin temperature measured by an embedded wire sensor (EWS), which is widely used in existing manikins, is theoretically higher than that of the wet skin fabric on the manikin where water evaporates. Therefore, we directly measured the surface temperature of the skin fabric using multiple thermistors (MT) and compared it with that of EWS. Four different work clothing ensembles were tested in an isothermal condition. The mean skin temperatures of MT were lower than those of EWS by 0.49, 0.62, 0.75, and 0.89°C, for the manikin walking at 0.00 (standing), 0.27, 0.53, and 0.80 m/s, respectively. Concomitantly, the real evaporative resistances using MT were lower than those using EWS by 9.1, 10.9, 12.5, and 14.4%. These results clearly show that the skin temperature of EWS should be corrected. In our thermal manikin, the temperature difference (TD) (°C) between MT and EWS was calculated for each of five parts: Arm, Trunk, Hip, Thigh, and Calf. The area-weighted average TD of the five parts was expressed as follows: TD = Heat Flux (W/m2) × 0.0092. This equation provides an estimate of TD without measuring surface skin temperature directly and helps to correct the evaporative resistance of clothing ensembles.

Effects of partial sleep restriction and subsequent daytime napping on prolonged exertional heat strain

Objectives It is considered that sleep restriction is one of the risk factors for the development of exertional heat stroke and illness. However, how sleep restriction affects exertional heat strain and the nature of the coping strategy involved in this phenomenon remain unclear. Methods Fourteen healthy subjects were studied on four occasions: after a night of normal sleep (NS, 7–8 h) and after a night of partial sleep restriction (PSR, 4 h), each with or without taking a daytime nap during the subsequent experimental day. The laboratory test consisted of two 40 min periods of moderate walking in a hot room in the morning and the afternoon. Results The increase in rectal temperature during walking was significantly greater in PSR than in NS in the afternoon. The rating scores for physical and psychological fatigue and sleepiness were significantly greater in PSR than in NS, both in the morning and in the afternoon. The reaction times and lapses in the psychomotor vigilance task (PVT) after walking were significantly worse in PSR than in NS in the morning and after lunch. The nap intervention attenuated significantly the scores for fatigue and sleepiness in PSR. Furthermore, the decreased PVT response in PSR was significantly reversed by the nap. Conclusions These results suggest that PSR augments physiological and psychological strain and reduces vigilance in the heat. Taking a nap seemed to be effective in reducing psychological strain and inhibiting the decrease in vigilance.

Testing Cold Protection According to EN ISO 20344: Is There Any Professional Footwear that Does Not Pass?

The present Comité Européen de Normalisation (CEN) and International Organization for Standardization (ISO) standards for safety, protective and occupational footwear EN ISO 20344-20347 classify footwear as cold protective by a pass/fail test where the limits are set for an allowed 10 degrees C temperature drop inside the footwear during 30 min at a temperature gradient of approximately 40 degrees C. It is questionable if a simple pass/fail test of this kind provides approved footwear that really protects the feet from cooling in exposures ranging from temperatures at +18 degrees C to as low as or even lower than -50 degrees C. This study selected for testing some professional footwear that could certainly not be considered as cold protective. Some footwear that could be used in cold was selected with as low insulation as the not cold-intended footwear. Also, a boot intended for cold was selected to be tested according to a modified standard at a temperature gradient of 70 degrees C. The footwear selection was based on insulation measurements with a thermal foot model. All footwear did pass the test. Although it is clear for the user that a sandal, a mesh shoe or a thin textile shoe is not cold protective, it is not as clear that an item of safety footwear, that has as low insulation as those mentioned above, could be classified as cold protective according to the present standards. Because of this, the user might have a deceptive feeling of safety and may be exposed to higher risks. As practically all professional footwear may pass this cold test, then the method/requirements should be radically changed or such a test should be removed from the standards.

Expansion of effective wet bulb globe temperature for vapor impermeable protective clothing

The wet bulb globe temperature (WBGT) is an effective measure for risk screening to prevent heat dISOrders. However, a heat risk evaluation by WBGT requires adjustments depending on the clothing. In this study, we proposed a new effective WBGT (WBGTeff*) for general vapor permeable clothing ensembles and vapor impermeable protective clothing that is applicable to occupants engaged in moderate intensity work with a metabolic heat production value of around 174W/m2. WBGTeff* enables the conversion of heat stress into the scale experienced by the occupant dressed in the basic clothing ensemble (work clothes) based on the heat balances for a human body. We confirmed that WBGTeff* was effective for expressing the critical thermal environments for the prescriptive zones for occupants wearing vapor impermeable protective clothing. Based on WBGTeff*, we succeeded in clarifying how the weights for natural wet bulb, globe, and air temperatures and the intercept changed depending on clothing properties and the surrounding environmental factors when heat stress is expressed by the weighted sum of natural wet bulb, globe, and air temperatures and the intercept. The weight of environmental temperatures (globe and air temperatures) for WBGTeff* for vapor impermeable protective clothing increased compared with that for general vapor permeable clothing, whereas that of the natural wet bulb temperature decreased. For WBGTeff* in outdoor conditions with a solar load, the weighting ratio of globe temperature increased and that of air temperature decreased with air velocity. Approximation equations of WBGTeff* were proposed for both general vapor permeable clothing ensembles and for vapor impermeable protective clothing.

Heat balance model for a human body in the form of wet bulb globe temperature indices

The purpose of this study is to expand the empirically derived wet bulb globe temperature (WBGT) index to a rational thermal index based on the heat balance for a human body. We derive the heat balance model in the same form as the WBGT for a human engaged in moderate intensity work with a metabolic heat production of 174W/m2 while wearing typical vapor-permeable clothing under shady and sunny conditions. Two important relationships are revealed based on this derivation: (1) the natural wet bulb and black globe temperature coefficients in the WBGT coincide with the heat balance equation for a human body with a fixed skin wettedness of approximately 0.45 at a fixed skin temperature; and (2) the WBGT can be interpreted as the environmental potential to increase skin temperature rather than the heat storage rate of a human body. We propose an adjustment factor calculation method that supports the application of WBGT for humans dressed in various clothing types and working under various air velocity conditions. Concurrently, we note difficulties in adjusting the WBGT by using a single factor for humans wearing vapor-impermeable protective clothing. The WBGT for shady conditions does not need adjustment depending on the positive radiant field (i.e., when a radiant heat source exists), whereas that for the sunny condition requires adjustments because it underestimates heat stress, which may result in insufficient human protection measures.

Editorial: New development of research on personal protective equipment (PPE) for occupational safety and health: New development of research on personal protective equipment (PPE) for occupational safety and health

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives (by-nc-nd) License. There exist various kinds of physical, chemical, and biological hazards in the workplace. To protect workers from these hazards, it is not controversial that environmental management measures to remove or reduce these harmful factors and to improve the quality of workplaces through an engineering approach are fundamental solutions. However, in reality, there are many work sites where such decisively effective measures cannot be applied. In such situations, a work management approach utilizing personal protective equipment (PPE) is considered an alternative and significant means for protecting the safety and health of workers. Recent industrial development, automation, and digitalization has led to increased safety and reduced need for personal protection at many workplaces, while there still remain a considerable number of jobs that continuously require protection and many countries where traditional work methods are prevalent. Simultaneously, the threats have changed and new types of risks have emerged due to changed processes, new chemicals and materials, and work routines. Thus, there are still several industries where the workers need to be protected from contamination within processes by utilizing PPE. So far, many types of PPE have been developed to tackle this scenario. Nevertheless, their effectiveness and usability still remain incomplete. Thus, a new breakthrough for PPE is currently required. Progress in advanced fiber materials, knitting and weaving technologies, fabric fabrication techniques, nanomaterials, and fiber composite materials technologies have been remarkable in recent years. Therefore, applying the results of these advanced technologies to the development of PPE is a highly promising approach. On the other hand, even though protection of targeted harmful factors is successfully achieved by using effective PPE, such high performance of protection is likely to entail additional workloads on workers. One of the main burdens is the thermal impact caused by evaporative resistance and thermal insulation derived from the characteristics of PPE materials. The higher the evaporative resistance and Editorial