Skin Wettedness Research Articles

Lower Maximal Skin Wettedness in Both Warm-Humid and Hot-Dry Environments with Advanced Age (PSU HEAT Project).

Maximum skin wettedness (ωmax) is the proportion of the body covered in sweat at the upper limit of compensable heat stress. It has yet to be determined how ωmax changes with aging. We examined variability in ωmax at the upper limit of compensable heat stress in warm-humid (WH) and hot-dry environments (HD) in young (Y, 18-29 yrs), middle-aged (MA, 40-60 yrs) and older (O, 65-89 yrs) adults during minimal activity (MinAct; ~1.8 METS) and in O subjects at rest. ωmax was calculated using partitional calorimetry for 27 Y (13F), 27 MA (16F), and 32 O (18F) at the previously determined upper limits of compensable heat stress in WH and HD environments. In WH environments, ωmax was greater in Y (0.69 ± 0.12) and MA (0.64 ± 0.20) compared to O (0.47 ± 0.14; both P<0.05), but not different between Y and MA (P=0.85). In HD environments, ωmax was greater in Y (0.52 ± 0.05) compared to O adults (0.40 ± 0.07; P<0.05), but not different between MA (0.48 ± 0.10) and Y or O (both P≥0.15). In O participants at rest, ωmax was lower than MinAct in WH (P<0.001) but not HD environments. These findings indicate that (1) ωmax is lower with advanced age across environments and (2) is lower at rest than during light activity in O in humid conditions. ωmax established herein for unacclimated adults during activities of daily living and older adults at rest may be used to model heat stress responses for these populations and environments.

Comparison and correction on calculation methods of clothing insulation based on thermal comfort

Clothing insulation is a major factor affecting human thermal comfort, and it is usually a fixed value when the clothing ensemble are determined in the standard. However, real clothing insulation is considerably affected by the environment and activity level (metabolic rate). Thus, the heat flow method for obtaining clothing insulation through thermal equilibrium between the skin layer and environment was proposed. Later, a non-contact method for easy acquisition of clothing insulation was proposed. The method was implemented via infrared imager. In this paper, above methods were compared and analysed based on experiment data. Three activity levels were considered, sedentary (1.0 met), walking at speed of 0.8 m/s (1.8 met), and 1.2 m/s (2.6 met). The feasibility and accuracy of above methods are discussed by comparing the PMV calculated by the clothing insulation with the actual thermal sensation (TSV) of the subjects obtained by questionnaire. The results showed that the non-contact method exhibited the highest prediction accuracy. Due to the sweating effect on skin temperature, the higher the activity levels, the lower the prediction accuracy. In this paper, a correction method of clothing insulation was proposed by using the temperature of face and neck and skin wettedness. After correction, the root means square error between the PMV and TSV decreased by 11 %.

High-temperature and thermal radiation affecting human thermal comfort and physiological responses: An experimental study

Hot environments with high temperatures and thermal radiation are to be found in heat treating, glass melting workshops, etc., which impacts worker thermal comfort and physiological responses. The motivation of this study was to explore the changes of thermal comfort in a high-temperature and thermal radiation environment. Four experimental cases were designed to simulate high temperatures and thermal radiation. Physiological parameters such as skin temperature, ear cancel temperature, heart rate, and weight loss were investigated. Evaporative heat losses and skin wettedness were calculated by Gagge's two node model or weight loss. The results showed that local and mean skin temperatures increased by approximately 4 °C during the exposure. Thermal sensation vote was positively correlated with WBGT. The dynamic relationship between human heat gain, evaporative heat loss and potential thermal risk was framed as Stage A, Stage B, and possibly Stage C. This study could provide the basic information and theoretical evidence for the thermal comfort and thermal risk in high-temperatures and thermal radiation environment.

Sunscreen does not alter sweating responses or critical environmental limits in young adults (PSU HEAT project).

Outdoor athletes often eschew using sunscreen due to perceived performance impairments, which many attribute in part to the potential for reduced thermoregulatory heat loss. Past studies examining the impact of sunscreen on thermoregulation are equivocal. The purpose of this study was to determine the effects of mineral and chemical-based sunscreens on sweating responses and critical environmental limits in hot-dry (HD) and warm-humid (WH) environments. Nine subjects (3 M/6 F; 25 ± 2 yr) were tested with 1) no sunscreen (control), 2) chemical-, and 3) mineral-based sunscreen. Subjects were exposed to progressive heat stress with either 1) constant dry-bulb temperature (Tdb) at 34°C and increasing water vapor pressure (Pa) (WH trials) or 2) constant Pa at 12 mmHg and increasing Tdb (HD trials). Subjects walked at 4.9 ± 0.5 metabolic equivalents (METs) until an upward inflection in gastrointestinal temperature was observed (i.e., the critical environmental limit). Compared with control (39.9 ± 3.0°C), critical Tdb was not different in mineral (39.2 ± 3.5°C, P = 0.39) or chemical (39.7 ± 3.0°C, P = 0.98) sunscreen trials in HD environments. Compared with control (18.8 ± 4.0 mmHg), critical Pa was not different in mineral (18.9 ± 4.8 mmHg, P = 0.81) or chemical (19.5 ± 4.6 mmHg, P = 0.81) sunscreen trials in WH environments. Sweating rates, evaporative heat loss, skin wettedness, and sweating efficiency were not different among the three trials in the WH (all P ≥ 0.48) or HD (all P ≥ 0.87) environments. Critical environmental limits are unaffected by sunscreen application, suggesting sunscreen does not alter integrative thermoregulatory responses during exercise in the heat.NEW & NOTEWORTHY Our findings demonstrate that neither sweating nor critical environmental limits were affected by mineral-based and chemical-based sunscreen applications. The rates of change in core temperature during compensable and uncompensable heat stress were not changed by wearing sunscreen. Evaporative heat loss, efficiency of sweat evaporation, skin wettedness, and sweating rates were unaffected by sunscreen. Sunscreen did not alter integrative thermoregulatory responses during exercise in the heat.

Thermal sensation prediction model for high-speed train occupants based on skin temperatures and skin wettedness.

Passenger thermal comfort in high-speed train (HST) carriages presents unique challenges due to factors such as extensive operational areas, longer travel durations, larger spaces, and higher passenger capacities. This study aims to propose a new prediction model to better understand and address thermal comfort in HST carriages. The proposed prediction model incorporates skin wettedness, vertical skin temperature difference (ΔTd), and skin temperature as parameters to predict the thermal sensation vote (TSV) of HST passengers. The experiments were conducted with 65 subjects, evenly distributed throughout the HST compartment. Thermal environmental conditions and physiological signals were measured to capture the subjects' thermal responses. The study also investigated regional and overall thermal sensations experienced by the subjects. Results revealed significant regional differences in skin temperature between upper and lower body parts. By analyzing data from 45 subjects, We analyzed the effect of 25 variables on TSV by partial least squares (PLS), from which we singled out 3 key factors. And the optimal multiple regression equation was derived to predict the TSV of HST occupants. Validation with an additional 20 subjects demonstrated a strong linear correlation (0.965) between the actual TSV and the predicted values, confirming the feasibility and accuracy of the developed prediction model. By integrating skin wettedness and ΔTd with skin temperature, the model provides a comprehensive approach to predicting thermal comfort in HST environments. This research contributes to advancing thermal comfort analysis in HST and offers valuable insights for optimizing HST system design and operation to meet passengers' comfort requirements.

Do cool shirts make a difference? The effects of upper body garments on health, fluid balance and performance during exercise in the heat

ObjectivesDue to climate change and major sport events in hot climate, temperature regulation during exercise is gaining relevance in professional and amateur sports. This study compares the effects of an upper body garment with water-soaked inlays, of a synthetic- and of a cotton shirt on health, fluid balance and performance during a high intensity exercise session in the heat.Methods32 healthy participants (age 25 ± 4 years; 15 women) were assigned to one of three upper body garments (cotton-shirt, synthetic-fiber-shirt, cooling-vest with water-soaked inlays) and underwent a high intensity steady state ergometer exercise test (Temperature 30.5 °C, frontal airflow 20 km/h, relative air-humidity 43 ± 13%). Time to exhaustion, physiologic parameters (inner ear temperature, heart rate, relative oxygen uptake, body weight, garment weight) and subjective data (perceived exertion, thermal sensation, skin wettedness, clothing humidity, feeling scale) were assessed. Time to exhaustion was analyzed using a survival time analysis. Other outcomes were evaluated using Kruskal-Wallis Tests and 95%-confidence-intervals.ResultsTime to exhaustion was not different between groups. Cooling-vests were heavier and led to lower inner ear temperature, lower thermal- and higher clothing-humidity-sensation at the start of exercise. Physiologic and subjective parameters showed no group differences at exercise termination.ConclusionsIn a realistic setting including frontal airflow, synthetic and cotton-fiber shirts reach comparable effects on health and thermoregulation and are perceived as equally comfortable. Although inducing a small pre-exercise cooling effect, a water-soaked garment induces a weight penalty and creates a less comfortable situation.

Examining Occupant-Comfort Responses to Indoor Humidity Ratio in Conventional and Vernacular Dwellings: A Rural Indian Case Study

Optimum indoor humidity is often associated with comfort and overall well-being. Occupant comfort is often evaluated with a focus on “thermal comfort” using the PMV (predicted mean vote), PDD (predicted percentage of dissatisfied), and adaptive thermal comfort models. Humidity-determined comfort parameters, like skin and respiratory comfort, are well acknowledged in the scientific community, but strangely not considered for indoor comfort computations. This study proposes a new computational approach for describing and evaluating humidity-related skin comfort in buildings using skin temperature, evaporative loss, and skin wettedness as critical parameters. The Development and validation of the computational model was demonstrated through a case study in a rural Indian context. The case study involves real-time monitoring of indoor environmental parameters and humidity-determined occupant comfort votes recorded through a novel aggregated humidity comfort vote method. The simulation results were compared with the community comfort/health survey. It was observed that, even at neutral skin temperatures, an increase in skin wettedness increases the thermal sensation vote. Clothing varies according to gender, community, and personal preferences, influencing physiological parameters which determine comfort. The acceptable humidity ratio was found to be in the range of 17.4 to 22.6 g-wv/kg-da for Indian participants. Including humidity-related comfort parameters in building simulation tools would aid in selecting building materials for improved indoor comfort.

A wireless physiological parameter monitoring system with a treatment feedback function during neonatal phototherapy

Objective. Neonatal jaundice is a common condition in the early stages of newborns, and phototherapy is a fast, safe and effective method that is used to treat it. However, recent studies have shown that phototherapy may elicit side effects in infants, such as hypothermia, hyperthermia and dehydration. To improve the quality of phototherapy and the prognosis of patients, the changes in neonatal physiological parameters during phototherapy should be monitored to give better feedback to pediatricians or the phototherapy system. However, the current standard of clinical care during neonatal phototherapy with hard-wired devices limits this realization. Approach. Here, we developed a prototype of a neonatal wearable device, which can wirelessly potentially monitor the jaundice value, transepidermal water loss, skin wettedness factor and body orientation during phototherapy, and conducted prototype validation experiments. We also set up user-friendly interfaces and an analysis system on custom software, all designed to make the future addition of data interfaces for treatment feedback functions easier. Main results. The preliminary in vitro experiment demonstrated the effectiveness of simultaneous monitoring of the required physiological parameters. And further suggestions and specific operations are discussed in terms of optimization of the treatment of neonatal jaundice. Significance. It is believed that the established system has the potential to provide a basis for future phototherapy nursing guidelines and physiological monitoring standards.

Influences of variable thermal exposures on walking thermal comfort in hot summer - Physio-psychological responses

To improve walkability in warm-biased cities, it is important to study thermal comfort experienced by walking pedestrians in complex urban continuums with variable microclimates. In this study, the heat exchange between a walking human body and its variable ambient was studied by measuring 70 human subjects' skin temperatures, sweating, heart rates, and surveying their mixed thermal perceptions, and monitoring the meteorological parameters in their immediate surroundings in two complex urban continuums. The extent of variable thermal exposures characterized by simultaneously varying wind and solar radiation during walking was described by the index Reverse Dynamic Thermal Environment (R_DTE), and its impacts on the physio-psychological responses of the human subjects were studied. It is concluded that about 36% of produced heat would be accumulated within the body during a 10 min' walking under variable thermal exposures with an air temperature over 28.0 °C. The sweating rate is highly related to the R_DTE rather than the mean skin temperature deviation from the neutral one (ΔTsk). An increased extent of variable thermal exposures significantly improves the thermal comfort when a walking person's skin wettedness (w) is over 0.4, whereas it causes discomfort when w is below 0.2. While some more work are still needed to further understand the dynamic thermal responses, these preliminary findings shed light on assessing and improving walking thermal comfort by creating variable thermal exposures in the urban continuums on hot days.

Transient thermal comfort and physiological responses following a step change in activity status under summer indoor environments

People always experience changes in their daily activities. However, previous dynamic thermal comfort studies have focused on the changes in environmental parameters. Transient subjective and physiological responses following a step change in the activity status have rarely been addressed. To address this, 21 healthy male subjects dressed at 0.5 clo underwent three sessions: sitting for 15 min, walking for 20 min, and sitting for 20 min under three typical summer indoor conditions (operative temperatures (Top) and relative humidity: 23 °C and 60 %, 26 °C and 50 %, and 29 °C and 40 %). There were two walking speeds: 2 and 4 km/h. In addition to subjective votes, physiological parameters such as metabolic rate, skin temperature, and skin wettedness were investigated. The variations in the rate of heat loss from the skin, the rate of heat storage (S), and the core temperature were analysed using the JOS-3 model. The results showed that S was above zero while walking because of the delay in sweating. The heat storage took more than 20 min to dissipate at a typical summer indoor Top (23–29 °C) after experiencing moderate activity intensities (2.2–3.4 met). People were more sensitive to changes in core temperature during the downstep of activity than during the upstep of activity. The findings from this study revealed patterns of change in thermal comfort following a step change in activity status, which can be used to expand the theory of dynamic thermal comfort.

A modelling framework for local thermal comfort assessment related to bicycle helmet use

Thermal discomfort due to accumulated sweat increasing head skin wettedness may contribute to low wearing rates of bicycle helmets. Using curated data on human head sweating and helmet thermal properties, a modelling framework for the thermal comfort assessment of bicycle helmet use is proposed. Local sweat rates (LSR) at the head were predicted as the ratio to the gross sweat rate (GSR) of the whole body or by sudomotor sensitivity (SUD), the change in LSR per change in body core temperature (Δtre). Combining those local models with Δtre and GSR output from thermoregulation models, we simulated head sweating depending on the characteristics of the thermal environment, clothing, activity, and exposure duration. Local thermal comfort thresholds for head skin wettedness were derived in relation to thermal properties of bicycle helmets. The modelling framework was supplemented by regression equations predicting the wind-related reductions in thermal insulation and evaporative resistance of the headgear and boundary air layer, respectively. Comparing the predictions of local models coupled with different thermoregulation models to LSR measured at the frontal, lateral and medial head under bicycle helmet use revealed a large spread in LSR predictions predominantly determined by the local models and the considered head region. SUD tended to overestimate frontal LSR but performed better for lateral and medial head regions, whereas predictions by LSR/GSR ratios were lower and agreed better with measured frontal LSR. However, even for the best models root mean squared prediction errors exceeded experimental SD by 18–30%. From the high correlation (R > 0.9) of skin wettedness comfort thresholds with local sweating sensitivity reported for different body regions, we derived a threshold value of 0.37 for head skin wettedness. We illustrate the application of the modelling framework using a commuter-cycling scenario, and discuss its potential as well as the needs for further research.

A modified method of the standard effective temperature (SET) based on the extended mean skin temperature index (EMSTI)

Among the existing thermal environment evaluation indexes, the standard effective temperature (SET) is based on the two-node model and performs better than the predicted mean vote (PMV) in non-neutral environments. However, previous studies show that the mean skin temperature and skin wettedness of the SET standard environment do not equal to the actual value, which violates the premise of SET. Moreover, it is found that the mean skin temperature of the standard environment differs from the actual value significantly under high temperature and humidity. Therefore, the applicability of SET in hot and humid environments deserves further study. The mean skin temperature is a superior evaluation index of thermal sensation in steady-state thermal environments with moderate temperature and humidity, and has been widely used in thermal sensation prediction. However, there also lacks in-depth research on the relationship between thermal sensation and mean skin temperature under high temperature and humidity. In this study, an extended mean skin temperature index (EMSTI) based on mean skin temperature combined with the maximum latent heat loss from skin surface is proposed through theoretical derivation. By verifying the index using the experimental data from different laboratories, it is shown that the proposed EMSTI can well evaluate the thermal sensation of hot and humid environments in different areas. The EMSTI is further used to represent thermal sensation to establish the equivalent relationship between the standard and actual environment, and the SET in hot-humid areas is modified.

Influence of sex and biological maturation on the sudomotor response to exercise-heat stress: are girls disadvantaged?

Both adult females and children have been reported to have a lower sweating capacity and thus reduced evaporative heat loss potential that may increase their susceptibility to exertional hyperthermia in the heat. Compared with males, females have a lower maximal sweat rate and thus a theoretically lower maximum skin wettedness due to a lower sweat output per gland. Similarly, children have been suggested to be disadvantaged in high ambient temperatures due to a lower sweat production and therefore reduced evaporative capacity, despite modifications of heat transfer due to physical attributes and possible evaporative efficiency. The reported reductions in the sudomotor activity of females and children suggest a lower sweating capacity in girls. However, because of the complexities of isolating sex and maturation from the confounding effects of morphological differences (e.g., body surface area-to-mass ratio) and metabolic heat production, limited evidence exists supporting whether children, and, more specifically, girls are at a thermoregulatory disadvantage. Furthermore, a limited number of child-adult comparison studies involve females and very few studies have directly compared regional and whole body sudomotor activity between boys and girls. This minireview highlights the exercise-induced sudomotor response of females and children, summarizes previous research investigating the sudomotor response to exercise in girls, and suggests important areas for further research.

Gender differences in metabolic rates and thermal comfort in sedentary young males and females at various temperatures

Human metabolic rate is a fundamental and essential aspect of thermal comfort, and gender differences in metabolic rate may underlie gender differences in comfort. This study explores gender differences in physiological and subjective responses to a wide range of cold to hot temperatures. Forty healthy college students (20 females and 20 males) participated in the experiments. Subjects were sedentary, wearing 0.6 clo, staying at 26 °C for 30 min, then exposed to either at cool (14, 16, 18, 20 °C), neutral (24, 26 °C), or warm (28, 30, 32, and 34 °C) temperatures for 90 min. Both subjective questionnaires (thermal sensation, thermal comfort, thermal acceptability) and physiological measurements (metabolic rate, skin temperature, skin blood flow, and skin wettedness) were collected during the exposures. Females tend to have lower metabolic rates than males at all temperatures, although significant differences were only found at 14, 16, and 18 °C. Females tend to be cooler and less comfortable than males at cool temperatures, which could be explained by the lower metabolic rates and lower skin temperatures in females. Males tend to be warmer and less comfortable at warm temperatures, which could be explained by higher metabolic rates and higher skin wettedness in males. No significant gender differences in subjective or physiological responses were found at neutral conditions.

Voluntary Cooling during Exercise Is Augmented in People with Multiple Sclerosis Who Experience Heat Sensitivity.

We tested the hypothesis that people with multiple sclerosis (MS) who experience heat sensitivity voluntarily engage in cool-seeking behavior during exercise to a greater extent than healthy controls. In a 27.0°C ± 0.2°C, 41% ± 2% RH environment, seven participants with relapsing-remitting MS who exhibited heat sensitivity and seven healthy controls completed two randomized trials cycling for 40 min (EX) at 3.5 W·kg-1 metabolic heat production, followed by 30 min recovery (REC). In one trial, participants were restricted from engaging in cooling (CON). In the other trial, participants voluntarily pressed a button to receive 2 min of ~2°C water perfusing a top (COOL). Mean skin and core temperatures and mean skin wettedness were recorded continuously. Total time in cooling provided an index of cool-seeking behavior. RPE, total symptom scores (MS only), and subjective fatigue (MS only) were recorded every 10 min. Core temperature (+0.5°C ± 0.1°C) and skin wettedness (+0.53 ± 0.02 a.u.) increased but were not different between groups or trials at end exercise (P = 0.196) or end recovery (P = 0.342). Mean skin temperature was reduced in COOL compared with CON at end exercise (P ≤ 0.002), with no differences between groups (P ≥ 0.532). MS spent more total time in cooling during EX (MS, 13 ± 3 min; healthy, 7 ± 4 min; P < 0.001) but not REC (MS, 2 ± 1 min; healthy, 0 ± 1 min; P = 0.496). RPE was greater at end exercise in MS (P = 0.001). Total symptom scores increased during exercise (P = 0.005) but was not different between trials (P = 0.321), whereas subjective fatigue was not attenuated in the cooling trial (P = 0.065). Voluntary cooling is augmented in MS but does not consistently mitigate perceptions of heat-related symptoms or subjective fatigue.

Voluntary Cooling‐Seeking Behavior during Heat Exposure is Decreased When Physical Effort is Required

Motivational deterrents increase the level of cold discomfort that an individual will tolerate prior to engaging in warm-seeking behavior. It is unknown if this is true for warm discomfort, due to differences in behavioral sensitivities during heat and cold exposure. Purpose: Test the hypothesis that the requirement to engage in physical effort (i.e., the motivational deterrent) to receive cooling during heat exposure attenuates voluntary cool-seeking behavior compared to when no physical effort was required. Methods: Twelve healthy adults (27±4 y, 4 females) underwent 2 h exposures to 41±1°C, 20±0% RH with 15 min work:rest intervals at ~4 METS on 3 occasions. The trial order was quasi-randomized. Subjects wore a tube-lined suit top able to perfuse cold water (2.1±0.2ºC). In the first trial, participants received no cooling (CON). The subsequent trials were randomized and subjects were given the option to freely engage in cool-seeking behavior by either 1) pressing a button to receive 2 min of cooling (BUTTON) or 2) receive cooling while producing 15% maximal isometric handgrip force for as long as desired (HG) or up to 2 min. A 1 min washout period followed each behavior. Mean skin (Tsk, 10 site) and core (Tcore, gastrointestinal pill) temperature, skin wettedness (Wsk, 10 site), forearm skin blood flow (SkBF, laser Doppler), and axilla and thigh local sweat rate (LSR, ventilated capsule) were recorded continuously. The total number of behaviors and cumulative cooling time indicated the amount of cool-seeking behavior between each trial. Results: Tcore, and Wsk increased over time (P<0.01) with no differences between trials (P≥0.28) or at the end of heat exposure (CON: +0.69±0.32ºC; BUTTON: +0.75±0.33ºC; HG: +0.62±0.26ºC, P=0.52). Tsk at the end of heat exposure was lowest in BUTTON (34.2±1.5°C) compared to HG (35.6±0.8°C, P=0.03) and CON (36.9±0.7°C, P<0.01). Axilla and thigh LSR, and SkBF increased over time (P<0.01) with no differences between trials (P≥0.11). The total number of behaviors (8±3 vs. 10±5, P=0.04) and cumulative cooling time (850±323 vs. 1230±616 seconds, P=0.02) were lower in HG compared to BUTTON. Conclusion : Motivational deterents can modulate behavioral thermoregulation during heat exposure such that, when physical effort is required to obtain cooling, the frequency and duration of cool-seeking behavior is reduced.

A study on the capacity of a ventilation cooling vest with pressurized air in hot and humid environments

Hot and humid working environments exist in civil engineering, exploration, shipping, and so on. Especially in mines and textile workplaces, the air humidity is usually close to saturation. Frontline workers perform physically demanding work, which will make the body sweat greatly and increase the occurrence of heat-related illnesses. The microenvironment under clothing can be improved by a ventilation cooling vest with pressurized air (denoted VCV), and the trunk skin temperature will be decreased. However, the amount of heat that a VCV removes from a working human body in hot and humid environments is unclear. In this study, human experiments were carried out, the ambient temperature was controlled at 30 °C, 32 °C or 34 °C, and the air humidity was 90%. The subjects wore a labor suit (denoted LS) or a VCV, running on a treadmill at 5 km/h or 7.5 km/h. The results showed that the total trunk heat loss was increased by 169–237%, and the cooling power of the VCV was between 79.5 and 97.6 W when wearing the VCV. However, the actual skin wettedness is often less than the calculated value, and the calculated cooling power should be considered the upper limit. The study indicated that the cooling capacity of the VCV increased as the ambient temperature and labor intensity increased, and the heat dissipation of the body also increased.

Predicted Mean Vote with skin wettedness from standard effective temperature model

Predicted Mean Vote (PMV) predicts thermal sensation for a group of people from the human thermal load, and is well recognized by thermal comfort standards for energy-efficient design of thermally comfortable buildings. However, the oversimplified skin evaporative heat loss in the thermal load calculation contributes to the frequently reported discrepancies between the PMV and the real thermal sensation vote. This study modifies the PMV by using the skin wettedness from the standard effective temperature model. The standard effective temperature model, with advanced human thermoregulation, reasonably predicts the skin wettedness based on the core temperature, skin temperature, and peripheral blood flow. The skin wettedness is used to calculate the skin evaporative heat loss to replace the oversimplified one. The modified PMV with the improved skin evaporative heat loss is validated by the largest thermal comfort database, i.e., ASHRAE Global Thermal Comfort Database II, for different types of climate, buildings, and HVAC systems. Compared with the original PMV, the modified PMV improves the overall accuracy and robustness in thermal sensation prediction by 64% and 32% respectively. This study contributes to improving the PMV for the updating of thermal comfort standards.

Monitoring Transepidermal Water Loss and Skin Wettedness Factor with Battery-Free NFC Sensor.

The transepidermal water loss (TEWL) and the skin wettedness factor (SWF) are considered parts of a key perspective related to skincare. The former is used to determine the loss of water content from the stratum corneum (SC), while the latter is used to determine the human skin comfort level. Herein, we developed two novel approaches: (1) determination of the TEWL and the SWF based on a battery-free humidity sensor, and (2) the design of a battery-free smart skincare sensor device tag that can harvest energy from a near field communication (NFC)-enabled smartphone, making it a battery-free design approach. The designed skincare device tag has a diameter of 2.6 cm and could harvest energy (~3 V) from the NFC-enabled smartphone. A series of experimental tests involving the participation of eight and six subjects were conducted in vivo for the indoor and outdoor environments, respectively. During the experimental analysis, the skin moisture content level was measured at different times of the day using an android smartphone. The TEWL and SWF values were calculated based on these sensor readings. For the TEWL case: if the skin moisture is high, the TEWL is high, and if the skin moisture is low, the TEWL is low, ensuring that the skin moisture and the TEWL follow the same trend. Our smart skincare device is enclosed in a 3D flexible design print, and it is battery-free with an android application interface that is more convenient to carry outside than other commercially available battery-based devices.

Thermal comfort and physiological responses with standing and treadmill workstations in summer

The study investigates human thermal comfort requirements when using standing and treadmill workstations. Twenty-eight subjects were exposed to four ambient temperatures (20, 23, 26, 29 °C) while conducting four activities (sitting, standing, walking at 1.0 km/h, and walking at 2.0 km/h). Physiological responses, including metabolic rate, skin temperature, and skin wettedness, were measured continuously, while subjective thermal comfort responses were surveyed. Treadmill workstation significantly increased human metabolic levels and reduced the associated environmental neutral temperatures. Using linear regressions, the predicted neutral temperatures are 24.3 °C (sitting), 23.3 (standing), 22.2 (walking 1 km/h), and 21.1 °C (walking 2 km/h), respectively. The 80% acceptable temperature range varied from 20.5 to 28.2 °C for sitting and standing, 20.0–26.9 °C for walking 1 km/h, and 17.6–26 °C for walking 2 km/h. PMV-PPD model was not able to predict human comfort accurately when using standing or treadmill workstations. Based on our findings, a temperature zone ranging from 20.5 to 26 °C is seen to satisfy the summer thermal requirements for over 80% occupants in a space containing a combination of sitting, standing, and treadmill workstations. However, providing personal comfort control would be necessary, given the substantial inter-individual differences.