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5.
  • Bohgard, Mats, et al. (författare)
  • Fysikaliska faktorer
  • 2008
  • Ingår i: Arbete och teknik på människans villkor. - 9789173650373 ; , s. 191-307
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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6.
  • Bohgard, Mats, et al. (författare)
  • Physical Factors
  • 2009
  • Ingår i: Work and Technology on Human Terms. - 9789173650588 ; , s. 191-306
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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7.
  • Broede, Peter, et al. (författare)
  • The Universal Thermal Climate Index UTCI Compared to Ergonomics Standards for Assessing the Thermal Environment
  • 2013
  • Ingår i: Industrial Health. - 1880-8026. ; 51:1, s. 16-24
  • Forskningsöversikt (refereegranskat)abstract
    • The growing need for valid assessment procedures of the outdoor thermal environment in the fields of public weather services, public health systems, urban planning, tourism & recreation and climate impact research raised the idea to develop the Universal Thermal Climate Index UTCI based on the most recent scientific progress both in thermo-physiology and in heat exchange theory. Following extensive validation of accessible models of human thermoregulation, the advanced multi-node 'Fiala' model was selected to form the basis of UTCI. This model was coupled with an adaptive clothing model which considers clothing habits by the general urban population and behavioral changes in clothing insulation related to actual environmental temperature. UTCI was developed conceptually as an equivalent temperature. Thus, for any combination of air temperature, wind, radiation, and humidity, UTCI is defined as the air temperature in the reference condition which would elicit the same dynamic response of the physiological model. This review analyses the sensitivity of UTCI to humidity and radiation in the heat and to wind in the cold and compares the results with observational studies and internationally standardized assessment procedures. The capabilities, restrictions and potential future extensions of UTCI are discussed.
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8.
  • Bröde, Peter, et al. (författare)
  • Deriving the operational procedure for the Universal Thermal Climate Index (UTCI)
  • 2012
  • Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 1432-1254 .- 0020-7128. ; 56:3, s. 481-494
  • Tidskriftsartikel (refereegranskat)abstract
    • The Universal Thermal Climate Index (UTCI) aimed for a one-dimensional quantity adequately reflecting the human physiological reaction to the multi-dimensionally defined actual outdoor thermal environment. The human reaction was simulated by the UTCI-Fiala multi-node model of human thermoregulation, which was integrated with an adaptive clothing model. Following the concept of an equivalent temperature, UTCI for a given combination of wind speed, radiation, humidity and air temperature was defined as the air temperature of the reference environment, which according to the model produces an equivalent dynamic physiological response. Operationalising this concept involved (1) the definition of a reference environment with 50% relative humidity (but vapour pressure capped at 20 hPa), with calm air and radiant temperature equalling air temperature and (2) the development of a one-dimensional representation of the multivariate model output at different exposure times. The latter was achieved by principal component analyses showing that the linear combination of 7 parameters of thermophysiological strain (core, mean and facial skin temperatures, sweat production, skin wettedness, skin blood flow, shivering) after 30 and 120 min exposure time accounted for two-thirds of the total variation in the multi-dimensional dynamic physiological response. The operational procedure was completed by a scale categorising UTCI equivalent temperature values in terms of thermal stress, and by providing simplified routines for fast but sufficiently accurate calculation, which included look-up tables of pre-calculated UTCI values for a grid of all relevant combinations of climate parameters and polynomial regression equations predicting UTCI over the same grid. The analyses of the sensitivity of UTCI to humidity, radiation and wind speed showed plausible reactions in the heat as well as in the cold, and indicate that UTCI may in this regard be universally useable in the major areas of research and application in human biometeorology.
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9.
  • Bröde, Peter, et al. (författare)
  • Heat gain from thermal radiation through protective clothing with different insulation, reflectivity and vapour permeability
  • 2010
  • Ingår i: International Journal of Occupational Safety and Ergonomics. - 2376-9130. ; 16:2, s. 231-244
  • Tidskriftsartikel (refereegranskat)abstract
    • The heat transferred through protective clothing under long wave radiation compared to a reference condition without radiant stress was determined in thermal manikin experiments. The influence of clothing insulation and reflectivity, and the interaction with wind and wet underclothing were considered. Garments with different outer materials and colours and additionally an aluminised reflective suit were combined with different number and types of dry and pre-wetted underwear layers. Under radiant stress, whole body heat loss decreased, i.e., heat gain occurred compared to the reference. This heat gain increased with radiation intensity, and decreased with air velocity and clothing insulation. Except for the reflective outer layer that showed only minimal heat gain over the whole range of radiation intensities, the influence of the outer garments’ material and colour was small with dry clothing. Wetting the underclothing for simulating sweat accumulation, however, caused differing effects with higher heat gain in less permeable garments.
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10.
  • Bröde, Peter, et al. (författare)
  • Heat transfer through protective clothing under symmetric and asymmetric long wave thermal radiation
  • 2008
  • Ingår i: Zeitschrift für Arbeitswissenschaft. - 0340-2444. ; 62:4, s. 267-276
  • Tidskriftsartikel (refereegranskat)abstract
    • This report considers results of an ED funded research on thermal properties ofprotective clothing and their use in the assessment of the thermal strain at work. In order to study the effects of the asymmetry oflong wave thermal radiation on the heat transfer through protective clothing, the heat loss under all-side and unilaterally applied radiation with the same incident radiant power of 279 W/m2 was measured with a thermal manikin and compared to a reference condition where mean radiant temperature was equal to air temperature. With exposure to radiation a lowered heat loss, i.e. heat gain for the whole covered body area was observed, which did not depend on radiant asymmetry for the dry as well as for the combined dry and evaporative heat loss, and which was attenuated when wearing a more insulating underwear. However, under one-sided radiation a more inhomogeneous spatial distribution occurred with higher heat gains and higher surface temperatures at the irradiated body parts. Practical Relevance The direction ofthermal radiation in the horizontal plane may be neglected when assessing the physiological heat strain in protective clothing by heat budget models. In contrast to this, it may be advisable to consider radiant asymmetries with respect to thermal comfort with low intensity radiation, and the most intense radiant source when assessing the risk of skin burns.
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12.
  • Bröde, Peter, et al. (författare)
  • Non-evaporative effects of a wet mid layer on heat transfer through protective clothing
  • 2008
  • Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 104:2, s. 341-349
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to assess the non-evaporative components of the reduced thermal insulation of wet clothing, experiments were performed with a manikin and with human subjects in which two layers of underwear separated by an impermeable barrier were worn under an impermeable overgarment at 20 °C, 80% RH and 0.5 ms-1 air velocity. By comparing manikin measurements with dry and wetted mid underwear layer, the increase in heat loss caused by a wet layer kept away from the skin was determined, which turned out to be small (5-6 Wm-2), irrespective of the inner underwear layer being dry or wetted, and was only one third of the evaporative heat loss calculated from weight change, i.e. evaporative cooling efficiency was far below unity. In the experiments with 8 males, each subject participated in two sessions with the mid underwear layer either dry or wetted, where they stood still for the first 30 minutes and then performed treadmill work for 60 minutes. Reduced heat strain due to lower insulation with the wetted mid layer was observed with decreased microclimate and skin temperatures, lowered sweat loss and cardiac strain. Accordingly, total clothing insulation calculated over the walking period from heat balance equations was reduced by 0.02 m2 °C W-1 (16%), while for the standing period the same decrease in insulation, representing 9% reduction only showed up after allowing for the lower evaporative cooling efficiency in the calculations. As evaporation to the environment and inside the clothing was restricted, the observed small alterations may be attributed to the wet mid layer’s increased conductivity, which, however, appears to be of minor importance compared to the evaporative effects in the assessment of the thermal properties of wet clothing.
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16.
  • Gao, Chuansi, et al. (författare)
  • Cooling vests with phase change material packs: the effects of temperature gradient, mass, and covering area
  • 2010
  • Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 53:5, s. 716-723
  • Tidskriftsartikel (refereegranskat)abstract
    • Phase change material (PCM) absorbs or releases latent heat when it changes phases, making thermal-regulated clothing possible. The objective of this study was to quantify the relationships between PCM cooling rate and temperature gradient, mass, and covering area on a thermal manikin in a climatic chamber. Three melting temperatures (24, 28, 32 °C) of the PCMs, different mass, covering areas, and two manikin temperatures (34 and 38 °C) were used. The results showed that the cooling rate of the PCM vests tested is positively correlated with the temperature gradient between the thermal manikin and the melting temperature of the PCMs. The required temperature gradient is suggested to be greater than 6 °C when PCM vests are used in hot climates. With the same temperature gradient, the cooling rate is mainly determined by the covering area. The duration of the cooling effect is dependent on PCM mass and the latent heat
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17.
  • Gao, Chuansi, et al. (författare)
  • Cooling vests with phase change materials: the effects of melting temperature on heat strain alleviation in an extremely hot environment
  • 2011
  • Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6327 .- 1439-6319. ; 111:6, s. 1207-1216
  • Tidskriftsartikel (refereegranskat)abstract
    • A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated.
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  • Gao, Chuansi, et al. (författare)
  • Gait muscle activity during walking on an inclined icy surface
  • 2008
  • Ingår i: Industrial Health. - : National Institute of Industrial Health. - 1880-8026 .- 0019-8366. ; 46:1, s. 15-22
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective of this study was to explain the contribution of lower extremity muscle activity to gait kinetic and kinematic adaptations for maintaining gait dynamic balance when walking on an inclined icy surface and the biomechanical mechanisms used to counteract slip risk. A two-way factorial experimental design was applied. The two independent variables were the walkway surface (ice and treadmill) and the walkway inclination (0º, 6º, 8º). The dependent variable was the amplitude of the surface EMG of four right lower extremity muscles (tibialis anterior TA, gastrocnemius lateralis GL, rectus femoris RF, and biceps femoris BF). Twelve healthy subjects (7 males and 5 females) participated in the walking trials. A two-way ANOVA analysis showed that on the icy surface in the heel contact phase, EMG amplitudes significantly decreased in TA and RF compared to those for the treadmill surface. In the mid-stance phase, the GL muscle activity significantly decreased on ice compared to treadmill and all four muscle activities increased significantly with the inclination. During the toe off phase, GL and RF activities increased with the inclination. The mechanisms identified may be applied to develop intervention, rehabilitation and training techniques, and to improve performance in human locomotion, such as for winter sports.
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20.
  • Gao, Chuansi, et al. (författare)
  • Initial, transient and steady state evaporative resistance of impermeable protective clothing
  • 2006
  • Ingår i: [Host publication title missing]. - 9623675348 ; , s. 253-261
  • Konferensbidrag (refereegranskat)abstract
    • The measured water vapour resistances of clothing ensembles differ among laboratories particularly for impermeable clothing. Due to the moisture transfer in the clothing ensemble, evaporative heat losses in initial, transient and steady state phases are different. The purpose of this study was to investigate moisture absorption inside underwear and outer layer as a function of time, to quantify the difference of water vapour resistance of protective clothing (impermeable outer layer and cotton underwear) in initial, transient and steady state. Manikin Tore was used by wearing wet ‘skin’ to simulate sweating. The evaporative resistance is found to be more than two times higher in the initial phase than that in the saturation phase. The moisture content is gained exponentially in the clothing ensemble. On the contrary, mass loss directly from the wet skin decreases exponentially. These may partly explain the poor reproducibility while measuring the evaporative resistance of impermeable clothing for a short period.
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21.
  • Gao, Chuansi, et al. (författare)
  • Moisture absorption, mass loss and evaporative resistance of permeable clothing in a transient condition
  • 2006
  • Ingår i: Journal of Donghua University. - 1672-5220. ; 23:5, s. 54-58
  • Tidskriftsartikel (refereegranskat)abstract
    • The water vapour resistance of clothing ensembles is not as commonly determined as dry thermal insulation. The measurement techniques are more complicated and the measurement values differ among laboratories. Due to complicated moisture transfer process through clothing ensemble, the moisture absorbed and evaporated varies in transient and steady state phases depending on properties, thickness of clothing, and environmental conditions. The purpose of this study was to measure moisture absorption inside hygroscopic underwear, hydrophobic and permeable outer wear as a function of time, to investigate mass loss from “skin” as well as from manikin, to quantify evaporative heat loss and total heat loss from manikin, to determine evaporative resistance of clothing. Manikin Tore was used by wearing wet “skin” to simulate sweating. Moisture content gain of the inner garment shows an exponential relation against time. Moisture in the outer permeable garment shows very small gain. On the contrary, mass loss directly from the wet skin decreases exponentially. The mass loss from the manikin is relatively stable throughout three test phases. The evaporative heat loss is about two thirds of the total heat loss from the sweating manikin. One hour measurement time is sufficient to get stable results while measuring the evaporative resistance of clothing ensembles with hygroscopic inner garment and permeable outer garment. The variation between the 1st hour and the 3rd hour is less than 5%. The length of transient period and measurement time requirement is dependent on the permeability, thickness of clothing ensembles and environmental conditions.
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  • Gao, Chuansi, et al. (författare)
  • Personal cooling with phase change materials to improve thermal comfort from a heat wave perspective
  • 2012
  • Ingår i: Indoor Air. - : Hindawi Limited. - 0905-6947. ; 22:6, s. 523-530
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract in UndeterminedAbstract The impact of heat waves arising from climate change on human health is predicted to be profound. It is important to be prepared with various preventive measures for such impacts on society. The objective of this study was to investigate whether personal cooling with phase change materials (PCM) could improve thermal comfort in simulated office work at 34°C. Cooling vests with PCM were measured on a thermal manikin before studies on human subjects. Eight male subjects participated in the study in a climatic chamber (T(a) = 34°C, RH = 60%, and ν(a) = 0.4 m/s). Results showed that the cooling effect on the manikin torso was 29.1 W/m(2) in the isothermal condition. The results on the manikin using a constant heating power mode reflect directly the local cooling effect on subjects. The results on the subjects showed that the torso skin temperature decreased by about 2-3°C and remained at 33.3°C. Both whole body and torso thermal sensations were improved. The findings indicate that the personal cooling with PCM can be used as an option to improve thermal comfort for office workers without air conditioning and may be used for vulnerable groups, such as elderly people, when confronted with heat waves. PRACTICAL IMPLICATIONS: Wearable personal cooling integrated with phase change materials has the advantage of cooling human body's micro-environment in contrast to stationary personalized cooling and entire room or building cooling, thus providing greater mobility and helping to save energy. In places where air conditioning is not usually used, this personal cooling method can be used as a preventive measure when confronted with heat waves for office workers, vulnerable populations such as the elderly and disabled people, people with chronic diseases, and for use at home.
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25.
  • Gao, Chuansi, et al. (författare)
  • Slips and falls in a cold climate: underfoot surface, footwear design and preference of preventive measures
  • 2008
  • Ingår i: Applied Ergonomics. - : Elsevier BV. - 1872-9126 .- 0003-6870. ; 39:3, s. 385-391
  • Tidskriftsartikel (refereegranskat)abstract
    • Slips and falls and associated outdoor injuries are prevalent in cold climates. The objectives of this field investigation were to describe the consequences of slips and falls on ice and snow and the associated injuries, to assess the risks of various icy and snowy surfaces, to identify design needs of footwear, and to ascertain preventive measure preferences of outdoor workers. The organizations investigated were a newspaper delivery service, a military regiment, mining and construction industries. The results showed that fall events occur most frequently on ice covered with snow. This is due to the difficulty of perceiving hidden risks in order to adjust gait strategies. The professional footwear provided does not provide enough protection against slips and falls. Slip resistant properties are ranked as one of the top requirements by the users. Their most preferred preventive measures are footwear with anti-slip properties and the application of anti-slip materials, such as sand or salt.
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26.
  • Gao, Chuansi, et al. (författare)
  • The comparison of thermal properties of protective clothing using dry and sweating manikins
  • 2006
  • Ingår i: [Host publication title missing].
  • Konferensbidrag (refereegranskat)abstract
    • The thermal insulation of clothing is commonly determined by dry thermal manikins either made of plastic or metal. For the determination of evaporative resistance of clothing ensemble, there exist three types of manikin methods: pre-wetted underwear or “skin” covered on dry manikins, the manikin with regulated constant water supply to the “skin” surface and the sweating fabric manikin based on a water filled body covered with waterproof but vapour permeable fabrics. The purpose of this study was to compare thermal insulation and moisture evaporative resistance of a set of protective clothing measured using different type of manikins. The total thermal insulation of seven EU project ensembles (Subzero A and B, Permeable (PERM), Impermeable (IMP), Nomex coverall (with two types of underwear) and Cotton coverall) were measured using the manikin Tore in Sweden, the sweating fabric manikin Walter in Hong Kong, and the manikin Newton in the UK. The results showed that total thermal insulation is reproducible for the seven clothing ensembles measured on the manikins Walter and Tore. The coefficient of variance is less than 8%. Nomex coverall with cotton underwear has 8-16% higher total insulation than that with polypropylene underwear. The apparent evaporative resistance of the impermeable coverall with cotton underwear measured on Newton was 44.5% lower than the evaporative resistance measured on Walter. The effect of condensation and conduction at room temperature environment and measuring time allowing full accumulation of moisture in clothing ensembles might be two important factors affecting the evaporative resistance.
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28.
  • Gao, Chuansi, et al. (författare)
  • The heating effect of phase change material (PCM) vests on a thermal manikin in a subzero environment
  • 2008
  • Ingår i: 7th International Meeting on Manikins and Modelling (7I3M).
  • Konferensbidrag (refereegranskat)abstract
    • The heating effects of three PCM vests (Tmelt=32, 28 and 24 °C) were tested on a thermal manikin with constant temperature at 30 ºC in a subzero environment (Ta=-4 °C, Va=0.4 m/s). The results showed that the heating effects lasted about 3-4 hours. The highest heating effects reduced heat loss for 20-30 W/m2 on the torso during the first two hours. The results also showed that the vest with higher melting/solidifying temperature had a greater and longer heating effect. Among the three wear scenarios, the PCM vest worn directly and closely over the stretch coverall without winter jacket revealed the highest heating effect on the torso.
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29.
  • Gao, Chuansi, et al. (författare)
  • Thermoregulatory manikins are desirable for evaluations of intelligent clothing and smart textiles
  • 2010
  • Ingår i: 8I3M : Eighth International Meeting for Manikins and Modeling : Victoria, BC, Canada, August 22-26, 2010 - Eighth International Meeting for Manikins and Modeling : Victoria, BC, Canada, August 22-26, 2010.
  • Konferensbidrag (refereegranskat)abstract
    • Thermal manikins have been used to measure thermal properties of clothing. The use of thermal manikins has made a step forward in terms of quantifying thermal properties of clothing in a 3-D manner compared with the use of hotplates for material testing. The effects of clothing properties measured on the thermal manikins under steady state (constant manikin surface temperature and constant environmental condition) have usually to be validated by human subject tests. The thermal insulation and evaporative resistance values measured in the constant conditions are also used in modeling to calculate heat balance, predict human thermal physiological responses, and thermal comfort. However, in many real life situations, clothing properties (e.g. moisture transfer), in particular the clothing properties with smart materials, e.g. phase change materials (PCMs), environmental conditions, sweating rate, skin temperatures are neither constant nor uniform. These make mathematical modeling complicated to take into account various transient, non-uniform conditions, and changeable properties of smart clothing which is becoming increasingly popular (Tang and Stylios 2006). Moreover, skin and core temperatures rather than heat loss or storage are commonly used to evaluate thermal comfort, define hypothermia and hyperthermia and evaluate heat strain. Therefore, the direct prediction of thermophysiological responses (skin and core temperatures) based on manikin measurements are valid (Psikuta and Rossi 2009), and could be considered another step forward towards direct evaluation of human-clothing-thermal environment interactions. In the case of measuring a personal cooling system, current standard specifies the measurement of the average heat removal rate from a sweating heated manikin (ASTM F2371-10). This heat removal rate is not constant for the PCMs. The objective of this study was to investigate the gap between the measured heat removal rate of smart clothing with PCMs obtained on a thermal manikin in a stable state, and clothing effects on local human skin and on core temperature, to compare the difference of the results obtained from both methods, and to highlight the need for developing intelligent thermoregulatory manikins.
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30.
  • Gao, Chuansi, et al. (författare)
  • Validation of standard ASTM F2732 and comparison with ISO 11079 with respect to comfort temperature ratings for cold protective clothing
  • 2015
  • Ingår i: Applied Ergonomics. - : Elsevier BV. - 1872-9126 .- 0003-6870. ; 46:Online 17 July 2014, s. 44-53
  • Tidskriftsartikel (refereegranskat)abstract
    • American standard ASTM F2732 estimates the lowest environmental temperature for thermal comfort for cold weather protective clothing. International standard ISO 11079 serves the same purpose but expresses cold stress in terms of required clothing insulation for a given cold climate. The objective of this study was to validate and compare the temperature ratings using human subject tests at two levels of metabolic rates (2 and 4 MET corresponding to 116.4 and 232.8 W/m(2)). Nine young and healthy male subjects participated in the cold exposure at 3.4 and -30.6 °C. The results showed that both standards predict similar temperature ratings for an intrinsic clothing insulation of 1.89 clo and for 2 MET activity. The predicted temperature rating for 2 MET activity is consistent with test subjects' thermophysiological responses, perceived thermal sensation and thermal comfort. For 4 MET activity, however, the whole body responses were on the cold side, particularly the responses of the extremities. ASTM F2732 is also limited due to its omission and simplification of three climatic variables (air velocity, radiant temperature and relative humidity) and exposure time in the cold which are of practical importance.
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31.
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32.
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33.
  • Geng, Q., et al. (författare)
  • Temperature limit values for touching cold surfaces with the fingertip
  • 2006
  • Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 1475-3162 .- 0003-4878. ; 50:8, s. 851-862
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: At the request of the European Commission and in the framework of the European Machinery Directive, research was performed in five different laboratories to develop specifications for surface temperature limit values for the short-term accidental touching of the fingertip with cold surfaces. Methods: Data were collected in four laboratories with a total of 20 males and 20 females performing a grand total of 1655 exposures. Each touched polished blocks of aluminium, stainless steel, nylon-6 and wood using the distal phalanx of the index finger with a contact force of 1.0, 2.9 and 9.8 N, at surface temperatures from +2 to -40 degrees C for a maximum duration of 120 s. Conditions were selected in order to elicit varying rates of skin cooling upon contact. Contact temperature (T-C) of the fingertip was measured over time using a T-type thermocouple. Results: A database obtained from the experiments was collated and analysed to characterize fingertip contact cooling across a range of materials and surface temperatures. The database was subsequently used to develop a predictive model to describe the contact duration required for skin contact temperature to reach the physiological criteria of onset of pain (15 degrees C), onset of numbness (7 degrees C) and onset of frostbite risk (0 degrees C). Conclusions: The data reflect the strong link between the risk of skin damage and the thermal properties of the material touched. For aluminium and steel, skin temperatures of 0 degrees C occurs within 2-6 s at surface temperatures of -15 degrees C. For non-metallic surfaces, onset of numbness occurs within 15-65 s of contact at -35 degrees C and onset of cold pain occurs within 5 s of contact at -20 degrees C. The predictive model subsequently developed was a non-linear exponential expression also reflecting the effects of material thermal properties and initial temperature. This model provides information for the protection of workers against the risk of cold injury by establishing the temperature limits of cold touchable surfaces for a broad range of materials, and it is now proposed as guidance values in a new international standard.
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34.
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35.
  • Ghaddar, Nesreen, et al. (författare)
  • Experimental and Theoretical Study of Ventilation and Heat Loss From Isothermally Heated Clothed Vertical Cylinder in Uniform Flow Field
  • 2010
  • Ingår i: Journal of Applied Mechanics. - : ASME International. - 0021-8936 .- 1528-9036. ; 77:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The flow characteristics and heat transfer are studied in a vertical annulus of a heated cylinder surrounded by a permeable cylinder, subject to cross uniform wind with open end to the environment and in the presence of natural convection. The objective here is to develop a computationally efficient model capable of capturing the physics of the flow and heat transport to predict air renewal rates in the vertical annulus. The small quantities of air infiltrating/exfiltrating through the porous cylinder over its upstream/downstream regions do not substantially affect the external flow pattern around the clothed cylinder. The air annulus flow and heat transport model predicted the radial and vertical mass fluxes and the mass flow rate at the opening as a function of environment conditions, porous cylinder thermal properties, wind speed, and annulus geometry. Experiments were performed in a low speed wind tunnel (0.5-5 m/s), in which an isothermally heated vertical cylinder surrounded by a clothed outer cylinder was placed in uniform cross wind. The tracer gas method is used to predict total ventilation flow rates through the fabric and the opening. Good agreement was found between the model and experimental measurements of air renewal rate and predicted heat loss from the inner cylinder at steady conditions. A parametric study is performed to study the effect of wind speed and temperature difference between the wind and skin temperature on induced ventilation through the clothing and the opening. It is found that natural convection enhances ventilation of the annulus air at wind speed, less than 3 m/s, while at higher speeds, natural convection effect is negligible. As the temperature difference between external wind and inner cylinder surface increases, the vertical air temperature gradient and total upward airflow through the opening increase.
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36.
  • Gudmundsson, Anders, et al. (författare)
  • Dust in Buildings - A Method for Identifying Particle Sources
  • 2005
  • Ingår i: Environmental ergonomics XI : proceedings of the 11th International Conference, 22-26 May, 2005, Ystad, Sweden - proceedings of the 11th International Conference, 22-26 May, 2005, Ystad, Sweden. - 9163170620 ; , s. 507-510
  • Konferensbidrag (refereegranskat)
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37.
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38.
  • Havenith, Bensahbat, et al. (författare)
  • The UTCI-Clothing Model
  • 2012
  • Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 1432-1254 .- 0020-7128. ; 56:3, s. 461-470
  • Tidskriftsartikel (refereegranskat)abstract
    • The Universal Thermal Climate Index (UTCI) was conceived as a thermal index covering the whole climate range from heat to cold. This would be impossible without considering clothing as the interface between the person (here, the physiological model of thermoregulation) and the environment. It was decided to develop a clothing model for this application in which the following three factors were considered: (1) typical dressing behaviour in different temperatures, as observed in the field, resulting in a model of the distribution of clothing over the different body segments in relation to the ambient temperature, (2) the changes in clothing insulation and vapour resistance caused by wind and body movement, and (3) the change in wind speed in relation to the height above ground. The outcome was a clothing model that defines in detail the effective clothing insulation and vapour resistance for each of the thermo-physiological model's body segments over a wide range of climatic conditions. This paper details this model's conception and documents its definitions.
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39.
  • Havenith, George, et al. (författare)
  • Apparent latent heat of evaporation from clothing: attenuation and “heat pipe” effects
  • 2008
  • Ingår i: Journal of Applied Physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 104:1, s. 142-149
  • Tidskriftsartikel (refereegranskat)abstract
    • Investigating claims that a clothed person’s mass loss does not always represent their evaporative heat loss (EVAP), a thermal manikin study was performed measuring heat balance components in more detail than human studies would permit. Using clothing with different levels of vapor permeability and measuring heat losses from skin controlled at 34°C in ambient temperatures of 10, 20, and 34°C with constant vapor pressure (1 kPa), additional heat losses from wet skin compared with dry skin were analyzed. EVAP based on mass loss (Emass) measurement and direct measurement of the extra heat loss by the manikin due to wet skin (Eapp) were compared. A clear discrepancy was observed. Emass overestimated Eapp in warm environments, and both under and overestimations were observed in cool environments, depending on the clothing vapor permeability. At 34°C, apparent latent heat ((lambda)app) of pure evaporative cooling was lower than the physical value ((lambda); 2,430 J/g) and reduced with increasing vapor resistance up to 45%. At lower temperatures, (lambda)app increases due to additional skin heat loss via evaporation of moisture that condenses inside the clothing, analogous to a heat pipe. For impermeable clothing, (lambda)app even exceeds (lambda) by four times that value at 10°C. These findings demonstrate that the traditional way of calculating evaporative heat loss of a clothed person can lead to substantial errors, especially for clothing with low permeability, which can be positive or negative, depending on the climate and clothing type. The model presented explains human subject data on EVAP that previously seemed contradictive.
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40.
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41.
  • Havenith, George, et al. (författare)
  • Evaporative Cooling: effective latent heat of evaporation in relation to evaporation distance from the skin
  • 2013
  • Ingår i: Journal of Applied Physiology. - 1522-1601. ; 114:6, s. 778-785
  • Tidskriftsartikel (refereegranskat)abstract
    • Calculation of evaporative heat loss is essential to heat balance calculations. Despite recognition that the value for latent heat of evaporation, used in these calculations, may not always reflect the real cooling benefit to the body, only limited quantitative data on this is available which has found little use in recent literature. In this experiment a thermal manikin (MTNW, Seattle) was used to determine the effective cooling power of moisture evaporation. The manikin measures both heat loss and mass loss independently allowing a direct calculation of an effective latent heat of evaporation (λeff). The location of the evaporation was varied: from the skin or from the underwear or from the outerwear. Outerwear of different permeabilities was used and different numbers of layers were used. Tests took place in 20ºC, 0.5 m.s-1 at different humidities and were performed both dry and with a wet layer allowing the breakdown of heat loss in dry and evaporative components. For evaporation from the skin λeff is close to the theoretical value (2430J.g-1), but starts to drop when more clothing is worn, e.g. by 11% for underwear and permeable coverall. When evaporation is from the underwear, λeff reduction is 28% wearing a permeable outer. When evaporation is from the outermost layer only, the reduction exceeds 62% (no base-layer) increasing towards 80% with more layers between skin and wet outerwear. In semi- and impermeable outerwear the added effect of condensation in the clothing opposes this effect. A general formula for the calculation of λeff was developed.
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42.
  • Henriksson, Otto, 1976-, et al. (författare)
  • Protection against cold in prehospital care : wet clothing removal or addition of a vapor barrier
  • 2015
  • Ingår i: Wilderness & environmental medicine (Print). - : Elsevier. - 1080-6032 .- 1545-1534. ; 26:1, s. 11-20
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: The purpose of this study was to evaluate the effect of wet clothing removal or the addition of a vapor barrier in shivering subjects exposed to a cold environment with only limited insulation available.METHODS: Volunteer subjects (n = 8) wearing wet clothing were positioned on a spineboard in a climatic chamber (-18.5°C) and subjected to an initial 20 minutes of cooling followed by 30 minutes of 4 different insulation interventions in a crossover design: 1) 1 woolen blanket; 2) vapor barrier plus 1 woolen blanket; 3) wet clothing removal plus 1 woolen blanket; or 4) 2 woolen blankets. Metabolic rate, core body temperature, skin temperature, and heart rate were continuously monitored, and cold discomfort was evaluated at 5-minute intervals.RESULTS: Wet clothing removal or the addition of a vapor barrier significantly reduced metabolic rate (mean difference ± SE; 14 ± 4.7 W/m(2)) and increased skin temperature rewarming (1.0° ± 0.2°C). Increasing the insulation rendered a similar effect. There were, however, no significant differences in core body temperature or heart rate among any of the conditions. Cold discomfort (median; interquartile range) was significantly lower with the addition of a vapor barrier (4; 2-4.75) and with 2 woolen blankets (3.5; 1.5-4) compared with 1 woolen blanket alone (5; 3.25-6).CONCLUSIONS: In protracted rescue scenarios in cold environments with only limited insulation available, wet clothing removal or the use of a vapor barrier is advocated to limit the need for shivering thermogenesis and improve the patient's condition on admission to the emergency department.
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43.
  • Henriksson, Otto, 1976-, et al. (författare)
  • Protection against cold in prehospital care : evaporative heat loss reduction by wet clothing removal or the addition of a vapour barrier - a thermal manikin study
  • 2012
  • Ingår i: Prehospital and Disaster Medicine. - 1049-023X .- 1945-1938. ; 26:6, s. 1-6
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction: In the prehospital care of a cold and wet person, early application of adequate insulation is of utmost importance to reduce cold stress, limit body core cooling, and prevent deterioration of the patient’s condition. Most prehospital guidelines on protection against cold recommend the removal of wet clothing prior to insulation, and some also recommend the use of a waterproof vapor barrier to reduce evaporative heat loss. However, there is little scientific evidence of the effectiveness of these measures.Objective: Using a thermal manikin with wet clothing, this study was conducted to determine the effect of wet clothing removal or the addition of a vapor barrier on thermal insulation and evaporative heat loss using different amounts of insulation in both warm and cold ambient conditions.Methods: A thermal manikin dressed in wet clothing was set up in accordance with the European Standard for assessing requirements of sleeping bags, modified for wet heat loss determination, and the climatic chamber was set to -15 degrees Celsius (°C) for cold conditions and +10°C for warm conditions. Three different insulation ensembles, one, two or seven woollen blankets, were chosen to provide different levels of insulation. Five different test conditions were evaluated for all three levels of insulation ensembles: (1) dry underwear; (2) dry underwear with a vapor barrier; (3) wet underwear; (4) wet underwear with a vapor barrier; and (5) no underwear. Dry and wet heat loss and thermal resistance were determined from continuous monitoring of ambient air temperature, manikin surface temperature, heat flux and evaporative mass loss rate.Results: Independent of insulation thickness or ambient temperature, the removal of wet clothing or the addition of a vapor barrier resulted in a reduction in total heat loss of 19-42%. The absolute heat loss reduction was greater, however, and thus clinically more important in cold environments when little insulation is available. A similar reduction in total heat loss was also achieved by increasing the insulation from one to two blankets or from two to seven blankets.Conclusion: Wet clothing removal or the addition of a vapor barrier effectively reduced evaporative heat loss and might thus be of great importance in prehospital rescue scenarios in cold environments with limited insulation available, such as in mass-casualty situations or during protracted evacuations in harsh conditions.
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44.
  • Henriksson, Otto, 1976-, et al. (författare)
  • Protection against cold in prehospital care — thermal insulation properties of blankets and rescue bags in different wind conditions
  • 2009
  • Ingår i: Journal of Prehospital and Disaster Medicine. ; 24:5, s. 408-415
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction: In a cold,wet, or windy environment, cold exposure can be considerable for an injured or ill person. The subsequent autonomous stress response initially will increase circulatory and respiratory demands, and as body core temperature declines, the patient’s condition might deteriorate. Therefore, the application of adequate insulation to reduce cold exposure and prevent body core cooling is an important part of prehospital primary care, but recommendations for what should be used in the field mostly depend on tradition and experience, not on scientific evidence. Objective: The objective of this study was to evaluate the thermal insulation properties in different wind conditions of 12 different blankets and rescue bags commonly used by prehospital rescue and ambulance services. Methods: The thermal manikin and the selected insulation ensembles were setup inside a climatic chamber in accordance to the modified European Standard for assessing requirements of sleeping bags. Fans were adjusted to provide low (< 0.5 m/s), moderate (2–3 m/s) and high (8–9 m/s) wind conditions. During steady state thermal transfer, the total resultant insulation value, Itr (m2 °C/Wclo; where °C = degrees Celcius, and W = watts), was calculated from ambient air temperature (°C), manikin surface temperature (°C), and heat flux (W/m2). Results: In the low wind condition, thermal insulation of the evaluated ensembles correlated to thickness of the ensembles, ranging from 2.0 to 6.0 clo (1 clo = 0.155 m2 °C/W), except for the reflective metallic foil blankets that had higher values than expected. In moderate and high wind conditions, thermal insulation was best preserved for ensembles that were windproof and resistant to the compressive effect of the wind, with insulation reductions down to about 60–80% of the original insulation capacity, whereas wind permeable and/or lighter materials were reduced down to about 30–50% of original insulation capacity. Conclusions: The evaluated insulation ensembles might all be used for prehospital protection against cold, either as single blankets or in multiple layer combinations, depending on ambient temperatures. However, with extended outdoor, on-scene durations, such as during prolonged extrications or in multiple casualty situations, the results of this study emphasize the importance of using a windproof and compression resistant outer ensemble to maintain adequate insulation capacity.
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45.
  • Holmér, Ingvar (författare)
  • Assessment of cold exposure
  • 2001
  • Ingår i: International Journal of Circumpolar Health. - 2242-3982. ; 60, s. 413-422
  • Tidskriftsartikel (refereegranskat)
  •  
46.
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47.
  • Holmér, Ingvar, et al. (författare)
  • Breath Air Flow Rates During Treadmill Walking Using Filter Respirators
  • 2006
  • Ingår i: 13th International Conference of Respiratory Protection.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Respiratory minute volumes and instantaneous breath flow rates were measured in 8 subjects during treadmill work using (a) a particle filter respirator(Sundstroem SR200) and (b) a control breathing mask (Metamax I, Cortex). Work comprised five consecutive bouts of walking at 5 km/h with an increase in elevation of the treadmill by 5 % every 5 minutes. Minute ventilationincreased in a curvilinear manner with oxygen uptake and reached 88±20 and 93±20 l/min at 5 km/h (20%) with the control mask and SR200, respectively. Peak inspiratory flow rate (PIFR), measured as the average of several breath cycles (in 30 sec), was 273±38 for Control and 300±36 for SR200 at the same work rate. During standardized speech communication, minute volumes decreased. In contrast, PIFR increased by about 100 % at low work rates and about 30 % at 5 km/h (20%) compared to no speech condition, reaching a highest value of 373±42 for Control and 407±48 for SR200. The time of the inhalation cycle was between 50-60 % of the total breath cycle in Control and 46-53 in SR200. During speech inhalation time was 14 and 19 % at the lowest work rate for Control and SR200, respectively. Corresponding values for the highest work rate were 38 and 33 % of total breath time. At the highest work rate mean inspiratory flow rate was 192±43 l/min for SR200. It was calculated that at the three highest work rates the mask air flow rate exceeded 95 l/min for more than 60 % of the inhalation time. During speech conditions this result was valid also for the two lowest work rates.
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48.
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49.
  • Holmér, Ingvar, et al. (författare)
  • Classification of metabolic and respiratory demands in fire fighting activity with extreme workloads
  • 2007
  • Ingår i: Applied Ergonomics. - : Elsevier BV. - 1872-9126 .- 0003-6870. ; 38:1, s. 45-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Fire fighting work comprises work tasks requiring an energy yield at maximal or close to maximal levels of the individual. Due to the very nature of fire fighting more complex physiological variables are difficult to measure. We measured metabolic and respiratory responses in 15 male.. professional fire fighters during simulated work tasks on a test ground. Work time was on the average 22 min with individual components of work tasks lasting 2-4 min. The mean oxygen consumption for the whole exercise (22 min) was 2.75 +/- 0.291/min. The most demanding work task demanded an oxygen uptake of 3.55 +/- 0.271/min. Corresponding values for respiratory minute volumes were 82 +/- 14 and 102 +/- 141/min, respectively. Heart rates averaged 168 +/- 12 for the whole test and 179 +/- 13 beats/min for the heaviest work task. Two new classes for classification of intensive and exhausting, short term physical work are proposed for inclusion in ISO8996 and values for relevant parameters are proposed. (c) 2006 Elsevier Ltd. All rights reserved.
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50.
  • Holmér, Ingvar (författare)
  • Climat change and occupational heat stress: methods for assessment
  • 2010
  • Ingår i: Global Health Action. - 1654-9880. ; , s. 1-5
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Presumed effects of global warming on occupational heat stress aggravate conditions in many parts of the world, in particular in developing countries. In order to assess and evaluate conditions, heat stress must be described correctly and measured correctly. Objective: Assessment of heat stress using internationally recognized methods. Design: Two such methods are wet bulb globe temperature (WBGT; ISO 7243) and predicted heat strain (PHS; ISO 7933). Both methods measure relevant climatic factors and provide recommendations for limit values in terms of time when heat stress becomes imminent. The WBGTas a heat stress index is empirical and widely recognized. It requires, however, special sensors for the climatic factors that can introduce significant measurement errors if prescriptions in ISO 7243 are not followed. The PHS (ISO 7933) is based on climatic factors that can easily be measured with traditional instruments. It evaluates the conditions for heat balance in a more rational way and it applies equally to all combinations of climates. Results: Analyzing similar climatic conditions with WBGT and PHS indicate that WBGT provides a more conservative assessment philosophy that allows much shorter working time than predicted with PHS. Conclusions: Both methods should be used and validated worldwide in order to give reliable and accurate information about the actual heat stress.
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