Current knowledge on the effects of humidity on physiological and psychological responses

Kakitsuba, Naoshi

doi:10.1618/jhes.20.1

“…In these studies, dry‐wet (humid) scales (sensation of dryness) were used. Although no human mechanism for perceiving humidity has been found, 9 this does not mean that humans do not respond to low humidity. Decreased moisture content in a specific part of the body would cause some sensation that is different from the normal state, which is then reported as dryness, discomfort, and, sometimes, intolerance to humidity 2 .…”

Section: Introductionmentioning

confidence: 98%

Study on the lower limit of indoor humidity subject experiments on psychological responses

Takada

¹

2020

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As a basis for determining the lower limit of acceptable humidity in an indoor environment, experiments were conducted for 25 subjects to assess the maximum expected sensations of dryness, discomfort based on humidity, and intolerance based on humidity, under conditions of 26°C and 10% RH. As results, distinct negative evaluations (dry, uncomfortable, or intolerable) were not obtained as the majority response; however, a small number of subjects declared distinct negative responses. In addition to the whole‐body evaluation, the sensations for individual body parts were collected and found to be more intense for the eyes, nose, throat, and lips than for the other body parts. Significant differences between the genders were not found. For 8 of the subjects, similar experiments under a condition of 30% RH were conducted, and the difference between two humidity conditions was clearer for discomfort and intolerance than for dryness. The results suggest that the evaluation of the specific individuals who respond intensely, the consideration of intense responses for a specific part of the body, and the careful selection of an evaluation word for a psychological response might be effective to link this study to the determination of the lower limit of indoor humidity.

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“…However, evaporative heat loss decreases when humidity rises due to a reduced water vapor pressure gradient between the ambient air and the skin’s surface [ 1 ]. Such hot and humid condition significantly affects thermal comfort [ 3 ] and elevates skin temperature (T ) and core body temperature (T ) [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

Autonomic thermoregulatory responses and subjective thermal perceptions upon the initiation of thermal behavior among resting humans in hot and humid environment

Sedilla

¹

,

Maeda

²

2022

J Physiol Anthropol

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Background While thermoregulatory behavior is critical for maintaining homeostasis, our knowledge of behavioral thermoeffectors in humid heat is limited compared to the control of autonomic thermoeffectors. The predictions that the frequency and duration of intensified humid heat events are expected to increase in the coming years underline this shortcoming. Therefore, this study aims to elucidate the activation of autonomic thermoregulatory responses and subjective thermal perceptions upon deciding to initiate thermal behavior in a hot and humid environment. Methods Ten young male adults participated in an experimental trial where local cooling was permitted at any time during the behavioral assessment during passive exposure to humid heat. The air temperature and relative humidity were kept at 33$$^{\circ }$$ ∘ C and 80$$\%$$ % , respectively. Skin temperatures, core body temperature (T$$_{\text {core}}$$ core ), and skin blood flow (forearm, upper arm, and upper back) were obtained 120 s preceding thermal behavior. Local sweat rate (forearm and upper arm) and subjective thermal perceptions (neck and whole-body) upon thermal behavior initiation were also recorded. Results Mean skin temperature ($${\overline{\mathrm {T}}}_{\text {sk}}$$ T ¯ sk ) and T$$_{\text {core}}$$ core increased prior to thermal behavior initiation (p$$=$$ = 0.002; p$$=$$ = 0.001). An increase in mean body temperature ($${\overline{\mathrm {T}}}_{\text {body}}$$ T ¯ body ) was also observed (p < 0.001). However, the initiation of thermal behavior is not preceded by an increase in skin blood flow (p$$\ge$$ ≥ 0.154) and local sweat rate (p$$\ge$$ ≥ 0.169). An increase in thermal discomfort and skin wetness perception was observed (p$$\le$$ ≤ 0.048; p$$\le$$ ≤ 0.048), while thermal sensation did not differ from the baseline (p$$\ge$$ ≥ 0.357). Conclusion These findings suggest that when given the opportunity to behaviorally thermoregulate in a hot and humid environment, changes in skin blood flow and sweat rate are not required for thermal behavior to be initiated in resting humans. Moreover, an increase in $${\overline{\mathrm {T}}}_{\text {sk}}$$ T ¯ sk and T$$_{\text {core}}$$ core , which appears to cause an increase in thermal discomfort, precedes thermal behavior. In addition, an increase in $${\overline{\mathrm {T}}}_{\text {body}}$$ T ¯ body leading up to thermal behavior initiation was observed, suggesting that changes in $${\overline{\mathrm {T}}}_{\text {body}}$$ T ¯ body rather than $${\overline{\mathrm {T}}}_{\text {sk}}$$ T ¯ sk and T$$_{\text {core}}$$ core alone mediate thermal behavior in humid heat. Collectively, the results of this study appear to support the hypothesis that the temporal recruitment of autonomic thermoeffectors follows an orderly manner based on their physiological cost.

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“…The American Society of Heating, Refrigerating, and Air-Conditioning Engineers has determined the "acceptable range" as thermally neutral conditions based on the predicted mean vote (PMV), and it does not indicate the specific limit of low humidity, although discomfort caused by dryness due to low humidity is noted in the document (ASHRAE 2017). In other words, the threshold of humidity beyond which discomfort due to low humidity is experienced is yet to be determined (Derby et al 2017, Kakitsuba 2018): thus it must be experimentally investigated along with the influence of ambient air temperature.…”

Section: Introductionmentioning

confidence: 99%

Influence of temperature and humidity of ambient air on sensation of dryness during respiration

Takada

¹

2020

JHES

0

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To create an optimal indoor thermal environment, it is necessary to identify the environmental conditions that cause a sensation of dryness. Dryness is experienced in various parts of the human body such as the nose, mouth, throat, eyes, and skin: this study focuses on dryness in the airway. The relationship between the sensation of dryness and environmental factors such as the ambient air temperature and humidity (vapor pressure) was analyzed based on experiments performed on four subjects. This study analyzed the sensation of dryness experienced in six parts along the respiratory tract and the temperature of air inhaled/ exhaled at the airway aperture of each of the four subjects under different conditions of humidity and temperature maintained in an artificial climate chamber. The route of respiration was restricted to the nose or the mouth by blocking the other aperture. The experimental results revealed that the temperature of exhaled air was lower and the sensations of dryness in the nose, mouth, and throat were more intense in the case of low humidity under a constant temperature. These results suggest that an increase in the evaporation rate in the airway may cause a sensation of dryness. Further, the experimental results revealed that in the case of high temperature and constant vapor pressure, the sensation of dryness tended to be more intense. This suggests that higher ambient temperature increases the evaporation rate in the airway owing to the increase in the saturated vapor pressure in the inner surface of the airway.

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Current knowledge on the effects of humidity on physiological and psychological responses

Cited by 13 publications

References 72 publications

Study on the lower limit of indoor humidity subject experiments on psychological responses

Study on the lower limit of indoor humidity subject experiments on psychological responses

Autonomic thermoregulatory responses and subjective thermal perceptions upon the initiation of thermal behavior among resting humans in hot and humid environment

Influence of temperature and humidity of ambient air on sensation of dryness during respiration

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