TLV in cold environments

1. 1. The risks encountered during cold exposure are general body cooling or local cooling of parts of th body.

2. 2. Measures of cold stress must account for the effects of climate, clothing and metabolic heat production on heat balance.

3. 3. The combinaed effect of air temperature, mean radiant temperature, humidity and air velocity determines the cooling power of the environment.

4. 4. The cooling power can be easily converted into a required insulation value (IREQ) for whole body heat balance.

5. 5. Extensive cooling of hands and feet may be a limiting factor, even when sufficient total insulation is provided. In addition the cooling effect of wind on unprotected skin must be considered.

6. 6. Recommendation regarding acceptable exposures can be expressed as lowest ambient temperatures and time limits as function of available protection and activity level, with due attention to both general and local effects.

Responses of human skin temperature and thermal sensation to step change of air temperature

1. 1. The purpose of this paper is to clarify the non-linearity of the human physiological and psychological responses to step change of air temperature by impulse response analysis using Discrete Fourier Transformation.

2. 2. Experiments were conducted to investigate the effect of thermal transients on human responses.

3. 3. Experimental conditions were as follows: lowering air temperature from 30 to 20°C and raising air temperature from 20 to 30°C.

4. 4. The responses of local skin temperature on lowering air temperature from 30 to 20°C are not necessarily opposite to the responses found on raising air temperature from 20 to 30°C.

5. 5. From impulse response analysis using Discrete Fourier Transformation, skin temperature responses to the opposite air temperature change do not necessarily coincide with each other whenever the same temperature stimulus is occurred.

Bed climate of Korean using ondol heating system

1. 1. To examine the influence of different bed conditions (ondol sleep, bed sleep on ondol with same bedding) of the Korean ondol traditional heating system on human response during sleep, bed climates and physiological responses such as skin and rectal temperatures, weight loss, body movement and subjective sensation were measured with 4 grown-up females as subjects while they were sleeping for 7 h.

2. 2. Bed climate: Temperatures under the mattress and inside the quilt were higher on ondol while temperatures on the mattress and humidity inside the quilt were higher on the bed.

3. 3. Rectal temperature was significantly higher on ondol; skin temperature showed no major differences in relation to bed conditions. The frequency of body movements had the highest correlation with bed climate of the parameters measured.

4. 4. Mattress weight decreased on ondol and increased on the bed.

5. 5. The frequency of body movements was significantly higher in ondol sleep.

6. 6. The subjects sensation showed difference on cushion sensation between the two types of bed condition.

7. 7. To obtain the same level of comfort on both ondol and bed sleeping conditions less thermal insulating value is needed for ondol sleep.

Effect of hygroscopic fabrics on wear comfort in the fluctuating microclimate of clothing

1. 1. A new type of simulator for clothing microclimate was designed and constructed.

2. 2. The simulator was designed to simulate the humidity fluctuation of clothing microclimate as observed under light working conditions and to measure the surface temperature of sample fabrics against the skin by means of a radiation thermometer.

3. 3. Knitted fabrics of cotton and polyester, and polyethylene films were used as specimens with different hygroscopicities.

4. 4. The quick rise and fall in the surface temperature of cotton fabric was observed under rapid fluctuations of the microclimate humidity.

5. 5. Under the same humidity fluctuations, the temperature of polyester fabric rose and fell more moderately than that of cotton fabrics, and the temperature of the polyethylene film did not change. When the rate of change in stimulus temperature is higher, the threshold temperature of warm sensation of the skin comes closer to a given adaption temperature.

6. 6. Therefore, the rapid and large changes in the fabric temperature against the skin, which were observed especially for hygroscopic cotton fabric, must affect the thermal comfort of clothing.

Skin temperatures, thermosensory and pleasantness estimates in case of heterogeneity in the thermal environment

1. 1. Seven thermal conditions were imposed on male sitting subjects (slightly clothed: 0.6 clo).

2. 2. A thermal mannikin was also used to determine the exact operative temperature, T₀.

3. 3. Conditions were: uniform (UN: all parameters at 24.5°C, air velocity at 0.15 ms⁻¹), heated ceiling (HC at 45°C), heated floor (HF at 34°C), cold floor (CF at 14°C), two conditions of one cold wall at 6°C (CW1 and CW2 respectively with and without air temperature compensation) and increased air velocity (AV at 0.4 ms⁻¹).

4. 4. Local skin temperatures and answers to questionnaires were obtained.

5. 5. Skin temperature variations were affected by conditions and slight T₀ changes.

6. 6. Comfort judgments were fairly well related to T₀, especially when expressed as differences between actual non-uniform environment and the uniform one.

7. 7. It is concluded that, in case of non-uniform environments close to thermoneutral zone, thermal comfort or discomfort reflects the climate alterations better than the thermal sensation does.

Thermal sensations during simultaneous warming and cooling at theh forearm: A human psychophysical study

1. 1.The forearm of 5 female subjects ws thermally stimulated by 2 sets of interposed servo-thermodes that respectively drove skin temperature at ±0.1°C.s⁻¹ for 25 s and then held it constant. Mean skin temperature remained constant. The sequence was repeated at adapting temperatures between 22.5 and 37.5°C.

2. 2.Thermal sensations, continuously reported by the position of a dial, were warmer for heterogeneous thermal stimuli than for homogeneous stimuli when mean skin temperature was greater than 30°C and cooler when less than 27.5°C.

3. 3.This phenomenon is inconsistent with a single additive contribution of “warm” and “cold” information to thermal sensations.

Comparison of thermal responses with and without cold protective clothing in a warm environment after severe cold exposures

1. 1. Ten male students remained in a severely cold room (-25°C) for 20 min. thereafter, they transferred in a warm room (25°C) for 20 min.

2. 2. This pattern was repeated three times, total cold exposure time amounting to 60 min.

3. 3. In the warm room, the subjects removed their cold-protective jackets, or wore them continously.

4. 4. Rectal temperature, skin temperatures, manual performance and thermal comfort were measured during the experiment.

5. 5. Removing cold-protective jackets after severe cold exposure increased peripheral skin temperatures and reduced the discomfort in the warm room.

6. 6. However, these results were accompanied by a greater decrease in rectal temperature and manual performance.

7. 7. It is recommended that workers continue to wear cold-protective clothing in the warm areas outside of the cold storage to prevent decreases in deep body temperature and work efficiency caused by repated cold exposures.

Thermoregulatory responses of old men to gradual changes in ambient temperature

1. 1. Thermoregulatory respones to gradual rise and fall in the ambient temperature (T_a) were compared between 8 old (68–78 years) and 8 younger (20–25 years) male subjects.

2. 2. Starting at T_a of 31.5°C (r.h. 40%), T_a was raised to 39.5°C, then lowered to 21.5°C, and raised back to 31.5°C at a constant rate of 0.3°C/min.

3. 3. Noticeable differences in responses between the age groups were as follows: decline of sweating rate and reduction of acral blood flow during room cooling were retarded in the aged group, with wider variations among individuals, compared with those in the younger group; the tympanic and oesophageal temperatures fell considerably during cooling in the elderly group, failing to return to the level at start during the rewarming of the room, in contrast to the younger group.

4. 4. Such sluggish responses may be attributed largely to reduced cutaneous thermal perception with advancing age.

Heat stress and age: Skin blood flow and body temperature

1. 1. The ability to increase skin blood flow is an important mechanism for transferring heat from the body core to the skin for dissipation.

2. 2. During exercise, skin blood flow is typically 20–40% lower in men and women aged 55 and over (compared with 20–30 years old) at a given body core temperature. Yet criterion measures of heat tolerance (changes in core temperature, heat storage) often show minimal or no age-related alterations. From a series of studies conducted in our laboratory over the past 5 years, the following conclusions can be drawn.

3. 3. When fit healthy older subjects are matched with younger subjects of the same gender, size and body composition, V_O2max, acclimation state, and hydration level, age-related differences in skin blood flow are evident. However, these differences often do not translate into “poorer” heat tolerance or higher core temperatures.

4. 4. The larger core-to-skin thermal gradient maintained by the older individuals allows for effective heat transfer at lower skin blood flows.

5. 5. Furthermore, there is an increased coefficient of variation for thermoregulatory response variables with increasing age.

6. 6. Despite differences in the mechanisms underlying thermoregulation, true thermal tolerance is less a function of chronological age than of functional capacity and physiological health status.

7. 7. While this conclusion is based primarily on cross-sectional studies, it is supported by the results of more recent studies using multiple regression analyses.

8. 8. Implicit in this conclusion is the notion that thermal tolerance, at any age, is a modifiable individual characteristic.

The effects of wind and thermal radiation on thermal responses during rest and exercise in a cold environment

1. 1. The purpose of this study was to investigate the effects of thermal radiation and wind on thermal responses at rest and during exercise in a cold environment.

2. 2. The experimental conditions were radiation and wind (R + W), no radiation and wind (W), radiation and no wind (R), no radiation and no wind (C).

3. 3. The air temperature was −5°C. Thermal radiation was 360 W/m². Air velocities were 0.76, 1.73 and 2.8 m/s. Rectal and skin temperatures, heart rate and oxygen consumption were recorded. Thermal and comfort sensations were questioned.

4. 4. There are no significant effects of thermal radiation and wind on the physiological responses except the mean skin temperature. There are significant effects on the mean skin temperature (P < 0.01) and thermal sensation (P < 0.05).

A study on body temperature regulation and residential thermal environments of the elderly—II. residential thermal environments at the kansai district

1. 1. An investigation was carried out on 3 male and 4 female elderly people, from 65 to 78 years ol.d The first survey was made in August and September of 1990 (in summer) and the second in January and February of 1991 (in winter).

2. 2. Matters for investigation were human subjects and thermal environmental elements of houses which were recorded by a portable thermo-recorder and a vinyl resin globe thermometer. Dry bulb temperatures at a height of 0.1 and 1.2 m and wet bulb and globe temperatures at 1.2 m high were recorded in the living room, bedroom, toilet etc., the thermo-recorders which measured air and wet bulb temperatures were kept out of the sun.

3. 3. Data was recorded constantly for 7 days at 20 min intervals. Plans of houses and furniture arrangement which influence the thermal conditions were drawn from video recordings. Physical and psychological surveys of individuals were carried out over 2 days of daily life.

4. 4. Subjects carried the thermo-recorders (YM1, YM2) on their side. Rectal, back of hand, sole of foot and ambient temperatures were measured every 2 min and with thermistor sensors. At the same time, behaviour and clothes, assessment of thermal sensation, comfort sensation and sensation of estimated room temperature were reported.

5. 5. Thermal radiation was measured with thermographs during the winter. Human activity was recorded every minute for 33 h. This report is the result of surveys in summer and winter.

6. 6. The following results were obtained: (i) the air conditioning is used sometimes in the houses of the elderly; (ii) thermal sensation range reported is narrow; (iii) skin surface temperatures of the elderly are relatively high and their range of change is narrow, and the range of rectal temperature in a day is narrow; (iv) high activity and excessive heating cause a rise of rectal temperature and the rectal temperatures are lower at rest time.

Increased hand blood flow limits other skin vasodilation

1. 1. To examine whether the increased hand blood flow (BF), mainly arteriovenous anastomoses (AVA) flow, limits an increase in other skin BF during thermal load, 7 healthy male subjects were exercised for 25 min and then rested for 20 min in wrist occlusion (OCCL) and control experiments (CONT), respectively.

2. 2. In OCCL, both wrists were occluded at pressure of 250 mmHg from the 15th min of exercise.

3. 3. In CONT, the wrists were free throughout the experiment. Finger and forearm skin temperature greatly increased in CONT, but did not rise in OCCL.

4. 4. Suppressed hand BF in OCCL induced compensatory increases of skin BF and sweat rate in the chest at least.

5. 5. However, wrist occlusion induced a significant rise in esophageal temperature and a significant fall in mean arterial pressure (MAP).

6. 6. These results suggest that the rising hand BF greatly contributes to limit the increase in other skin BFs without any fall of MAP during thermal load.

Characteristics of wettedness under constant average skin temperature

1. 1. Experiments were carried out concerning the characteristics of wettedness revealed under constant average skin temperature using sitting-resting nude subjects. From the basic measurements of both environmental parameters and human physiological responses, the conclusions detailed below were proposed regarding the changes of wettedness under constant average skin temperature.

2. 2. There is positive correlation between the wettedness and environmental humidity, and negative correlation between the wettedness and air temperature.

3. 3. There is positive correlation between the evaporative heat loss from the skin surface and air temperature, and negative correlation between the evaporative heat loss and environmental humidity.

4. 4. There is negative correlation between the wettedness and evaporative heat loss.

5. 5. Wettedness is not constant but takes varying values, that is, corresponding to each average skin temperature both the maximum and the minimum wettedness values occur.

6. 6. Deriving from the items mentioned above, the theoretical locus of equal average skin temperature is not a straight line, but is a curved line plotted on the psychrometric chart.

Physiological responses and thermal sensations of the elderly in cold and hot environments

1. 1. 10 elderly and 10 college-aged females served as subjects in cold and heat environments. The subjects changed into the standard clothing (0.63 clo), and stayed in the neutral environment (25°C) for 23 min, thereafter they were exposed to the cold (10°C) or hot (35°C) environment for 49 min.

2. 2. Then they returned to the neutral environment, and stayed there for 47 min. Oral temperature, skin temperatures at 10 sites, blood pressure and thermal sensation were measured during the experiments.

3. 3. In the cold environment, the elderly could not reduce heat loss by vasoconstriction as did young people, and their blood pressures increased more rapidly than in young people. In the hot environment, the elderly could not promote heat loss by vasodilation as did young people. Moreover, there is a delayed sensitivity to cold for the elderly. Therefore, in the houses of the elderly, it is important to have heating and cooling systems which also includes the areas where the people do not stay for a long period of time (e.g. toilet, passageways).

Estimation of thermal sensation using PMV and SET under high air movement conditions

1. 1. Our previous experimental results showed the thermal sensation vote was much less than the values of PMV and SET^* at air velocities above 0.5 m/s.

2. 2. The method to modify SET^* is presented from the results of subjective experiments taking account of decrease in clo value of summer clothing and decrease in skin wettedness due to increased air velocity.

3. 3. Thermal resistance under increased air movement on a standard summer clothing ensemble was measured. Basic thermal insulation of the summer ensemble was reduced by 25% at air velocity of 1.0 m/s.

4. 4. Thirty-two subjects were exposed at operative temperatures of 27 and 30°C under 1 m/s air movement in order to determine the amount of skin diffusion. Measured evaporation heat loss from skin surface was much smaller at air velocity of 1 m/s than that predicted by SET^*.

5. 5. Estimated thermal sensation vote using modified SET^* agreed well with our previous experimental results under different air velocities for the same clothing.

An experimental study on the effect of humidity on thermal sensations of people in summer

1. 1. The authors propose humidity reduction instead of lowering room temperature in order to reduce cooling syndrome.

2. 2. They conducted experiments with subjects in the rooms, one with controlling humidity to about 40% r.h. and another without humidity control. Air-conditioning system with humidity control has a greater promise in making a comfortable environment, even at the temperature as high as 30°C, in comparison with conventional means using temperature control alone.

3. 3. Relationship of actual mean votes on temperature sensation and comfort sensation with PMV and SET, respectively, suggests that Japanese people might be more sensitive to humidity than Westerners and so different methods from those used in the western countries should be required for human thermal environmental studies with respect to the hot humid summer in Japan.

Thermal parameters of four species of Gerbillurus

1. 1.Thermal parameter of the four Gerbillurus species measured in the laboratory were examined in relation to their micro-environments in a xeric habitat.

2. 2.Basal metabolic rates (BMR) were lower than predicted, while thermoneutral zonds (TNZ) were narrow and exceeded burrow temperatures.

3. 3.Body temperatures (T_b) were regulated over a range of ambient temperatures (T_a). Evaporative water loss was used as a short-term cooling mechanism to reduce hyperthermia above the TNZ.

4. 4.Conductance was low below the TNZ to reduce heat loss.

5. 5.Adaptation to low temperatures is important for gerbils when active at night.

6. 6.The adaptive significance of the thermal biology of Gerbillurus is discussed in relation to phylogeny, distribution, food availability and nocturnal activity.

Effect of warm rearing on temperature regulation in resting and exercising rats

1. 1.|Hypothalamic and rectal temperatures were recorded in 8 warm-reared (wr) and in 12 warm-acclimated control rats during resting in the heat and during 30 min running under thermoneutral conditions.

2. 2.|Brain and body temperatures of wr rats were significantly higher (P < 0.001) than control rats, both in normothermia as well as in hyperthermia; at rest, and also during exercise.

3. 3.|Warm-reared rats were more tolerant to heat.

4. 4.|During normothermia a weak selective brain cooling was present in control but absent in wr rats. During hyperthermia, however, the cooling intensified in control and occurred in wr rats.

5. 5.|The main strategy of adaptation to heat in wr rats is an upward resetting of the temperature set-point and increased passivity.

Mismatch between temperature preferences and morphology in F1 hybrid newts (Triturus carnifex×T. dobrogicus)

1. The influence of interspecific hybridization on temperature preferences and morphology was examined in newts, Triturus carnifex and Triturus dobrogicus, before and after metamorphosis.

2. Thermoregulatory behavior was measured in an aquatic thermal gradient (5–32.5 °C) during 24 h.

3. Hybrid temperature preferences were similar to preferences of maternal species in both premetamorphic larvae and recently metamorphosed individuals.

4. Hybrid morphology (i.e., forelimb length and axilla–groin distance) was intermediate relative to parental species.

5. The mismatch between morphology and thermal preference in hybrid phenotypes indicates potential hybrid disadvantage in both intermediate and parental habitats.