Effects of heated seat and foot heater on thermal comfort and heater energy consumption in vehicle

Subjective experiments involving 12 different conditions were conducted to investigate the effects of heated seats and foot heaters in vehicles on thermal sensation and thermal comfort. The experimental conditions involved various combinations of the operative temperature in the test room (10 or 20°C), a heated seat (on/off) and a foot heater (room operative temperature +10 or +20°C). The heated seat and foot heater improved the occupant's thermal sensation and comfort in cool environments. The room operative temperature at which the occupants felt a 'neutral' overall thermal sensation was decreased by about 3°C by using the heated seat or foot heater and by about 6°C when both devices were used. Moreover, the effects of these devices on vehicle heater energy consumption were investigated using simulations. As a result, it was revealed that heated seats and foot heaters can reduce the total heater energy consumption of vehicles. Statement of Relevance: Subjective experiments were conducted to investigate the effects of heated seats and foot heaters in vehicles on thermal comfort. The heated seat and foot heater improved the occupant's thermal sensation and comfort in cool environments. These devices can reduce the total heater energy consumption in vehicles.

Comparison of heat dissipation response between Malaysian and Japanese males during exercise in humid heat stress

This study investigated the differences in heat dissipation response to intense heat stress during exercise in hot and humid environments between tropical and temperate indigenes with matched physical characteristics. Ten Japanese (JP) and ten Malaysian (MY) males participated in this study. Subjects performed exercise for 60 min at 55% peak oxygen uptake in 32°C air with 70% relative humidity, followed by 30 min recovery. The increase in rectal temperature (T(re)) was smaller in MY during exercise compared to JP. The local sweat rate and total body mass loss were similar in both groups. Both skin blood flow and mean skin temperature was lower in MY compared to JP. A significantly greater increase in hand skin temperature was observed in MY during exercise, which is attributable to heat loss due to the greater surface area to mass ratio and large number of arteriovenous anastomoses. Also, the smaller increase in T(re) in MY may be explained by the presence of a significantly greater core-skin temperature gradient in MY than JP. The thermal gradient is also a major factor in increasing the convective heat transfer from core to skin as well as skin blood flow. It is concluded that the greater core-skin temperature gradient observed in MY is responsible for the smaller increase in T(re).

Comparison of thermoregulatory responses to heat between Malaysian and Japanese males during leg immersion

The objective of this study was to investigate thermoregulatory responses to heat in tropical (Malaysian) and temperate (Japanese) natives, during 60 min of passive heating. Ten Japanese (mean ages: 20.8 ± 0.9 years) and ten Malaysian males (mean ages: 22.3 ± 1.6 years) with matched morphological characteristics and physical fitness participated in this study. Passive heating was induced through leg immersion in hot water (42°C) for 60 min under conditions of 28°C air temperature and 50% RH. Local sweat rate on the forehead and thigh were significantly lower in Malaysians during leg immersion, but no significant differences in total sweat rate were observed between Malaysians (86.3 ± 11.8 g m(-2) h(-1)) and Japanese (83.2 ± 6.4 g m(-2) h(-1)) after leg immersion. In addition, Malaysians displayed a smaller rise in rectal temperature (0.3 ± 0.1°C) than Japanese (0.7 ± 0.1°C) during leg immersion, with a greater increase in hand skin temperature. Skin blood flow was significantly lower on the forehead and forearm in Malaysians during leg immersion. No significant different in mean skin temperature during leg immersion was observed between the two groups. These findings indicated that regional differences in body sweating distribution might exist between Malaysians and Japanese during heat exposure, with more uniform distribution of local sweat rate over the whole body among tropical Malaysians. Altogether, Malaysians appear to display enhanced efficiency of thermal sweating and thermoregulatory responses in dissipating heat loss during heat loading. Thermoregulatory differences between tropical and temperate natives in this study can be interpreted as a result of heat adaptations to physiological function.

Physiological strains of wearing aluminized and non-aluminized firefighters' protective clothing during exercise in radiant heat

This study examined the influences of aluminized (Type A) and non-aluminized firefighters' protective clothing (Type B, C, D and CON) on physiological and subjective responses in radiant heat. Total clothing weight was 6.24, 6.38, 6.06, 5.76 and 3.82 kg for Type A, B, C, D and CON, respectively. Eight firefighters performed exercise at an air temperature of 30°C with 50%RH. Three bouts of 10 min-bicycle exercise in radiant heat (a globe temperature of 70°C) was spaced by a 10 min rest with no radiant heat. Results showed that rectal temperature, mean skin temperature, heart rate, and body weight loss were significantly greater in Type A than in other types (p<0.05). For Type A, thermal gradient of the body reached 0.0 ± 0.7°C, heart rate showed a maximum level of 183 ± 11 bpm and 1.9% of body weight was lost due to sweat secretion. Firefighters felt the hottest and most discomfort in Type A. It appeared that firefighters' thermoregulatory mechanism was severely challenged by wearing aluminized protective clothing during exercise in strong radiant heat. Therefore, it is suggested that the safe upper limits while wearing aluminized firefighters' clothing should be distinguished from those for typical firefighters' protective clothing.

Linguistic dimensions in descriptors expressing thermal sensation in Korean: 'warm' projects thermal comfort

The present study was triggered by the inconsistency in verbal descriptors in English and Korean describing 'warm' and 'hot' in the thermal sensation scale. The purpose of this study was to examine the linguistic dimensions of the terms expressing 'ttatteuhada (warm)' and 'yakkan duptta (slightly hot)' in Korean. A total of 988 urban Koreans (479 males and 509 females) participated in a questionnaire survey consisting of six questions. The one-to-one survey was conducted indoors in December 2008. Our results showed that (1) 'warm' and 'slightly hot' in Korean are distinctive thermal descriptors; (2) 'warm' projects thermal comfort (80.4% of 988 respondents), but 'slightly hot' projects some thermal discomfort (54.3% of 988 respondents); (3) a slight thermally comfortable feeling was expressed as 'warm' (83.9% of 988 respondents), while a slight thermally uncomfortable feeling was seldom expressed as 'warm' (6.2% of 988 respondents) in mild heat environments; (4) the linguistic dimension within the term 'warm' was less affected by individual thermal susceptibility (vulnerability) than that of the term 'slightly hot'. In summary, 'warm' in Korean connotes a thermally comfortable feeling. In the case of being a little thermally uncomfortable, Koreans project their thermal sensation through the term 'slightly hot', rather than 'warm'. In conclusion, thermal descriptors in the ISO 10551/ASHRAE scale, i.e., 'very cold-cold-cool-slightly cool-neutral-slightly warm-warm-hot-very hot', are not valid for the evaluation of mild hot environments in Korea. A new categorical scale is required in Korean considering the descriptors 'warm' and 'slightly hot'.

Combined factors effect of menstrual cycle and background noise on visual inspection task performance: a simulation-based task

It is well known that women are physiologically and psychologically influenced by the menstrual cycle. In addition, the presence of background noise may affect task performance. So far, it has proven difficult to describe how the menstrual cycle and background noise affect task performance; some researchers have found an increment of performance during menstruation or during the presence of noise, others found performance deterioration, while other still have reported no dominant effect either of the menstrual cycle in performance or of the presence of noise. However, no study to date has investigated the combinational effect between the menstrual cycle and the presence of background noise in task performance. Therefore, the purpose of this study was to examine the combined factor effect of menstrual cycle and background noise on visual inspection task performance indices by Signal Detection Theory (SDT) metrics: sensitivity index (d') and response criteria index (beta). For this purpose, ten healthy female students (21.5+/-1.08 years) with a regular menstrual cycle participated in this study. A VDT-based visual inspection task was used for the experiment in 3x2 factorial designs. Two factors, menstrual phase, pre-menstruation (PMS), menstruation (M), and post-menstruation (PM) and background noise, with 80 dB(A) background noise and without noise, were analyzed as the main factors in this study. The results concluded that the sensitivity index (d') of SDT was affected in all the menstrual cycle conditions (p<0.01) and the presence of background noise (p<0.05) but no combinational effect of menstrual cycle and background noise was found in this study. On the other hand, no significant effect was observed in the subject's tendency in visual inspection, shown by beta along the menstrual cycle and the presence of background noise. According to the response criteria for each individual subject, the presence of noise affected the tendency of some subjects in detecting the object and making decision during the visual inspection task.

Issues in combining the categorical and visual analog scale for the assessment of perceived thermal sensation: methodological and conceptual considerations

Typically, the scales for the measurement of thermal sensation have been formatted as categorical scales (CS). Emerging is the use of CS combined with visual analog scale (VAS) for the measurement of thermal sensation to improve the sensitivity of scales. However, reports are rare comparing the typical CS, standard VAS, and combined CS with VAS. Methodological and conceptual issues are arising with the combining of scales, but there are insufficient reports about the advantages and limitations of different scales. The present study compared 9-points categorical scale (9pts CS), VAS, and CS combined with VAS (graphic CS) through a questionnaire survey (n=988) and a controlled experiment during exercise (17 male subjects). Our results showed that graphic CS was more closely related to indoor air temperature for resting residents rather than VAS or 9pts CS. Around thermal neutral zone indoor environments, sensitivity to discriminate thermal sensation was the greatest for graphic CS. In particular, questionnaire responses to VAS showed a remarkable clustering around the thermal neutral zone. For dynamic exercising subjects, mean skin temperature was more closely related to graphic CS than 9pts CS. Our results indicated that graphic CS seemed to be more valid and sensitive than 9pts CS or VAS for the measurement of thermal sensation, but there are many issues to be considered when combining CS and VAS from the methodological and conceptual view points: definitions of terms, verbalizing with descriptors, number of category, scoring length, unipolar/bipolar construction, language translation, central terms, both anchor terms, orientation, color, etc. The above methodological and conceptual issues were discussed.

Effects of saliva collection using cotton swab on cortisol enzyme immunoassay

Cotton swabs are among the most commonly used devices for collecting saliva, but various studies have reported that their use impacts the results of salivary cortisol assays. These studies, however, estimated this impact by comparing the average of the concentration and/or scatter plots. In the present study, we estimated the impact of cotton swabs on the results of salivary cortisol enzyme immunoassay (EIA) by Bland-Altman plot. Eight healthy males (aged 20-23 years) provided four saliva samples on different days to yield a total of 32 samples. Saliva samples were collected directly in plastic tubes using plastic straws and then pipetted onto cotton swabs (cotton saliva collection) and into clear sterile tubes (passive saliva collection). There was a lower correlation between cotton and passive saliva collection. Individually, four subjects showed a negative correlation between passive and cotton saliva collection. A Bland-Altman plot indicated that cotton swabs causes a proportional bias on the EIA assay result. Our findings indicate a considerable effect of using cotton swabs for saliva collection, and subject-specific variability in the impact. A Bland-Altman plot further suggests possible reasons for this effect.

Effects of setting up of humidifiers on thermal conditions and subjective responses of patients and staff in a hospital during winter

The purpose of this survey was to measure the thermal environment in a hospital during winter, and to investigate the subjective responses of patients and staff via a questionnaire. The air temperature and humidity in the sickrooms and nurse stations were measured for 3 months during winter. After 2 months, we introduced humidifiers into about half of the rooms and nurse stations as a method of improving the environment, and evaluated the effects of the installed humidifiers on the thermal conditions. In all, 36 patients and 45 staff members were asked once a week about subjective symptoms (dry and itchy skin, thirst, etc.). Before setting up the humidifiers, the existence of a low-humidity environment in the hospital during winter was confirmed, with the levels of relative humidity and humidity ratio reaching under 50% and 5g/kg DA, respectively, which is known to promote the spread of influenza viruses. However, the introduction of the humidifiers increased the relative humidity in sickrooms from 32.8% to 43.9% on average, and the air humidity in sickrooms thus almost reached the optimum range suggested by the Hospital Engineering Association of Japan (HEAJ). Additionally, complaints of thermal discomfort and dryness of air decreased among the staff, though not among the patients, after the humidifiers were installed. These results suggest that introducing humidifiers into a hospital during winter is an effective method of improving the low-humidity environment and relieving the discomfort of staff members.

Effects of worn-out soles on lower limb stability, shock absorption and energy cost during prolonged walking

This study investigated the effects of worn-out shoes on lower leg stability, shock absorption and energy cost during prolonged walking. Seven male subjects (23.4 +/- 0.5 yr) walked at 4.8 km/h for 60 minutes wearing three different pairs of shoes: two of these pairs had severely and moderately worn soles (EASC: Excessive Attrite Shoe Condition and MASC: Moderate Attrite Shoe Condition, respectively) and the other pair had no wear (NASC: No Attrite Shoe Condition). Impact acceleration at the subtalar at heel strike, rearfoot angles (the subtalar joint and the lower leg) during stance phase, and oxygen uptake (VO2) were measured throughout the 60-minute walk. At the 10th minute of walking, worn-out shoes increased the supination of the subtalar joint and extortion of the lower leg. In addition, VO2 was significant larger in EASC (808.3 ml x min(-1)) than in NASC (749.5 ml x min(-1)). During the 60-minute walk, however, there were no time effects of shoe condition on the rearfoot angles and on VO2. In contrast, impact acceleration at the subtalar joint in EASC remained almost constant until the 30th minute of walking, and then began to elevate. In conclusion, worn-out shoes increased the energy cost and reduced lower leg stability during walking, although these changes were not influenced by walking duration within 60 minutes. However, prolonged walking showed the potential negative effect of worn-out shoe on shock absorption.

Environmental and behavioral conditions of bathing among elderly Japanese

This study investigated the bathing conditions of elderly Japanese, and sought to find factors relating to regional differences in death rates from bathtub accidents. A questionnaire survey was carried out in 11 areas of Japan. Questionnaires including questions regarding the length of time since houses had been built, types of facilities, and subjects' indoor thermal sensations and behavior while bathing were distributed to detached houses in each area twice, once in summer and once in winter. Completed questionnaires were collected from approximately 160 elderly people over 65 years old. Information regarding thermal sensations of rooms in winter revealed that a prefabricated bath and insulating window glass eased the cold in the bathroom. Unexpectedly, more subjects in the southern region than in the northern region reported being cold or a little cold while bathing in winter. In the present study, thermal sensations and behaviors while bathing seemed to be more affected by facilities and the location of houses than by the sex and age of the subjects.

Physiological and Subjective Responses to Low Relative Humidity in Young and Elderly Men

In order to compare the physiological and the subjective responses to low relative humidity of elderly and young men, we measured saccharin clearance time (SCT), frequency of blinking, hydration state of the skin, transepidermal water loss (TEWL), sebum level recovery and skin temperatures as physiological responses. We asked subjects to evaluate thermal, dryness and comfort sensations as subjective responses using a rating scale. Eight non-smoking healthy male students (21.7+/-0.8 yr) and eight non-smoking healthy elderly men (71.1+/-4.1 yr) were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25 degrees C and a relative humidity (RH) of 50%. The test-room conditions were adjusted to provide 25 degrees C Ta and RH levels of 10%, 30% and 50%. RH had no effect on the activity of the sebaceous gland or change of mean skin temperature. SCT of the elderly group under 10% RH was significantly longer than that of the young group. In particular, considering the SCT change, the nasal mucous membrane seems to be affected more in the elderly than in the young in low RH. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain greater than 30% RH, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain greater than 10% RH. On the thermal sensation of the legs, at the lower humidity level, the elderly group felt cooler than the young group. On the dry sensation of the eyes and throat, the young group felt drier than the elderly group at the lower humidity levels. From the above results, the elderly group had difficulty in feeling dryness in the nasal mucous membrane despite being easily affected by low humidity. On the other hand, the young group felt the change of humidity sensitively despite not being severely affected by low humidity. Ocular mucosa and physiology of skin by dryness showed no difference by age. In the effect of longer exposure (180 min.) to low RH, only TEWL showed a slight decrease after 120 minutes in 30% RH, and all the measured results showed no noticeable differences compared with the result at 120 minutes.

Physiological and Subjective Responses to Low Relative Humidity

In order to investigate the influence of low relative humidity, we measured saccharin clearance time (SCT), frequency of blinking, heart rate (HR), blood pressure, hydration state of skin, transepidermal water loss (TEWL), recovery sebum level and skin temperature as physiological responses. We asked subjects to judge thermal, dryness and comfort sensations as subjective responses using a rating scale. Sixteen non-smoking healthy male students were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25 degrees C and a relative humidity (RH) of 50%. The test room conditions were adjusted to provide a Ta of 25 degrees C and RH levels of 10%, 30% and 50%.RH had no effect on the activity of the sebaceous gland and on cardiovascular reactions like blood pressure and HR. However, it was obvious that low RH affects SCT, the dryness of the ocular mucosa and the stratum corneum of the skin and causes a decrease in mean skin temperature. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin, and the mean skin temperature decreases. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain an RH greater than 30%, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain an RH greater than 10%. Subjects felt cold immediately after a change in RH while they had only a slight perception of dryness at the change of humidity.

Decay of heat acclimation during exercise in cold and exposure to cold environment

Sixteen male students exercised for 14 days (1 h/day) in the heat for heat acclimation (HA). During deacclimation (DA) one group exercised in the cold (EXG, n=8) for 60 min/day (morning) and was exposed to the cold for another hour (afternoon) for 14 days. The other group was exposed to the cold (EPG, n=8) for 1 h each in the morning and afternoon (Ta: 18.0 degrees C, RH: 58%) over the same period. All returned to exercise in the heat for reacclimation (RA) for 10 days. Subjects were tested on days 1, 16, 21, 32, 36 and 44 on a bicycle ergometer for 60 min at 60% of VO(2max) in the heat (Ta: 31.1 degrees C, RH: 70%). Rectal temperature (T (re)) and heart rate (HR) at 40 min of exercise were used to determine the decay/gain of HA, which was calculated using the formula described by Pandolf et al. (Ergonomics, 20:399-408, 1977). After HA (day 16) T (re) and HR decreased significantly. During DA, EXG showed decay in T (re) of 24 and 35% and HR of 29 and 35% on days 21 and 32, respectively. For EPG the corresponding decay was of 2 and 9% for T (re) and 17 and 17% for HR. After 10 days of RA, EXG showed gains of 11% in T (re) and 12% in HR, while EPG showed gains of 47% in T (re) and 38% in HR. In conclusion, EXG had greater decay during DA and lower gains in RA compared to EPG. However, the differences between groups were significant only for T (re) after 4 days of DA.

Effects of ambient temperature steps on thermal comfort requirements

The purpose of this study was to determine the thermal comfort requirements for steps in temperature. Thirty male subjects were exposed for 50 min to a 34 or 37 degrees C condition, and then quickly transferred to a cooler environment of 31, 28, 25, and 22 degrees C for 50 min. Mean skin temperature was continuously measured, and the subjects reported their thermal sensation and comfort sensation every 2 min. Just after the step changes, the mean skin temperature immediately decreased, while the thermal sensation overshot and gradually rose again. Both the skin temperature and the thermal sensation seemed to reach a constant level within about 20 min. However, there were differences in the mean skin temperature and the neutral temperature derived from the correlation between the ambient temperature and the thermal sensation even 50 min after the steps, due to the thermal environmental condition before the changes of temperature. The change in the neutral temperature with time was expressed as two attenuating equations. These equations indicate that there is an obvious difference between the neutral temperatures due to the thermal condition before step changes, and that it takes >50 min after the step changes to reach the steady state. It is expected that these equations predict in quantitative terms the thermal comfort requirements within a given experimental condition.

Thermal environment and subjective responses of patients and staff in a hospital during winter

The purpose of this study was to ascertain the actual conditions of the thermal environment and the symptoms of patient and staff (nurses and nurses' aides) during winter in a hospital. We measured the ambient temperature and humidity in sickrooms, nurse stations, and corridors. The subjects included 36 patients and 45 staff members. The existence of low humidity environments (relative humidity was less than 40%) in a hospital during winter was confirmed, and the levels of low humidity reached those known to promote the spread of influenza viruses. Thermal comfort of patients was not directly connected to the low humidity in sickrooms. However, 54.9% and 73.4% of patients were conscious of itchy skin and thirst, respectively. The majority of the staff members were working with itchy skin and thirst. These results suggested that extreme low humidity in a hospital during winter presents problem that should be solved quickly.

Thermal sensation and comfort during exposure to local airflow to face or legs

The present study examined the contribution of local airflow temperature to thermal sensation and comfort in humans. Eight healthy male students were exposed to local airflow to their faces (summer condition) or legs (winter condition) for 30 minutes. Local airflow temperature (Tf) was maintained at 18 degrees C to 36 degrees C, and ambient temperature (Ta) was maintained at 17.4 degrees C to 31.4 degrees C. Each subject was exposed to 16 conditions chosen from the combination of Tf and Ta. Based on the results of multiple regression analysis, the standardized partial regression coefficient of Tf and Ta were determined to be 0.93 and 0.13 in the summer condition, and 0.71 and 0.36 in the winter condition at the end of the exposure. Also, thermal comfort was observed to depend closely on the interrelation between Tf and Ta. The present data suggested that local airflow temperature is an important thermal factor regarding thermal sensation and comfort.

Work in Artificial Cold Environments

The physiological characteristics of work in cold stores, as a typical artificial cold environment, are reviewed mainly from our various field and experimental studies. There are about 4,000 cold stores in Japan, and 85% of them are kept at temperatures below -20 degrees C. Although the duration of cold exposure per stay in a cold store was very short, forklift workers entered the cold stores very frequently. Cold stress and the decrease in workers' performance were the same as for continuous exposure to cold. Since the peripheral skin temperature of subjects at night is higher than that in the afternoon, they are less likely to feel cold or pain sensation at night. However, there was a marked decrease in rectal temperature and in manual performance. There is an increased risk of both hypothermia and accidents for those who work at night. The cold store workers, however, had adapted to cold through daily repeated cold exposures.