14.Raimundo Portugal

8/10/2019 14.Raimundo Portugal

1/11

THERMOPHYSIOLOGICAL RESPONSE OF HUMAN BEINGS WORKING INCOLD THERMAL ENVIRONMENTS

A. M. Raimundo1, A. V. M. Oliveira2, A. R. Gaspar1and D. A. Quintela1

1Department of Mechanical Engineering, University of Coimbra, Rua Lus Reis Santos, Plo II3030 - 788 Coimbra, email: [email protected] Portugal, http://www.dem.uc.pt

2Department of Mechanical Engineering, Polytechnic Institute of Coimbra, Rua Pedro Nunes,Quinta da Nora, 3030-199 Coimbra, Portugal, http://www.isec.pt

Summary: In this work, the simulation of heat and mass transfer from an individual working in cold thermalenvironments such as those frequently occurring in the Portuguese cold industrial activities is presented. Threedifferent typical cold conditions were selected corresponding to freezing chambers, refrigerating cold stores andcool controlled air temperature manufacturing workplaces.

To obtain the present results a numerical procedure based on a modified version of the Stolwijkthermoregulation model was used. Taking into account the temporal evolution of skin, rectal, lungs andhypothalamus temperatures, a study was presented where it is analyzed the thermophysiological difference

between a human being working indoors in three cold spaces. For each kind of cold space two or three differentsituations were selected: (i) the real situation, with the individual wearing inappropriate clothing insulation,associated to longer exposition times and shorter recovering periods than the recommended values; (ii) one idealscenario, with the human being wearing proper clothing for the real exposure and recover times; (iii) another idealcase, with the worker following the times of exposure and of recover recommend for the real clothing insulationthat he wears.

The results clearly show that, for the low temperatures characteristic of the freezing chambers associated withdeficient clothing insulation, prolonged exposures and insufficient recovering periods, the physiological strain ofhuman beings working on those conditions is amplified when compared to the ideal situations above described.For the other two cases, refrigerating cold stores and manufacturing workplaces, the most frequent scenario ischaracterized by the use of ensembles with an insulation value greater than the recommended. In short, deepchanges in the protection clothing used are required, particularly when a long time is needed to complete the worktasks.

Keywords: human thermoregulation model, cold stress, cold working places, clothing insulationCategory:Case studies, Human thermal physiology and mathematical models

1. Introduction

The hazards of cold stress include health effects,physiological adjustments, psychological responses andbehavioural reactions that have to be considered. ISO12894 [1] addresses these matters and summarizes themain illnesses that can arise from changes in body heatstorage. Particular attention is given to the effects of thegeneral hypothermia, to the local cold injuries and to

other health effects related to cold conditions, namely tothe cardiovascular, respiratory and metabolicphysiological responses. Thus, the activities developed inthe cold have to be evaluated in multiple perspectives.

Cold stress is related with the increase of heat need tomaintain the body in thermal equilibrium. The mostcommon indices used to characterize cold stress levelare the Wind Chill index [2] and the required clothinginsulation, known as IREQ index [3, 4]. On the one hand,since the Wind Chill index is more appropriated to predictthermal discomfort outdoors, it is not recommended forthe present study. On the other hand, the IREQ indexhas been widely used in indoors cold environments

evaluations. It is based on the global human body heatbalance in terms of the environmental conditions (air and

mean radiant temperature, air velocity and humidity), theprotection provided by clothing (thermal insulation andvapour permeability) and the person activity (metabolicrate). However, as stated by Holmr [5], cold stressshould be evaluated not only in terms of whole bodycooling, but also on local cooling (extremity, respiratory,convective and conductive skin cooling). As recognizedin ISO 11399 [6] and by Gavhed and Holmr [7],Griefahn [8] and so on, the IREQ index is not sufficient to

a complete characterization of cold stress and must becomplemented with other methods of analysis, namelyfield studies and the use of thermoregulation models.

Different research studies have been developed inorder to characterise the actual indoor working conditionsthrough field measurements. The research activitiescarried out in Japan (Tochiara [9], Kim et al. [10]), inDenmark (Nielsen [11]), and in Portugal (Oliveira et al.[12]) can be referred as examples of this approach.

The thermophysiological models are widely used in thestudy of thermal comfort under moderate thermalenvironments. Its application to the analysis of coldstress is only attempted by a few authors. Xu and Werner[13] achieved good compatibility between their 6segments thermoregulation model and experimental

7th International Thermal Manikin and Modelling Meeting - University of Coimbra, September 2008


2/11

results for the interaction between the human body,clothing and cold environments. Huizenga et al. [14]validated their 16 segments thermoregulation modelcomparing the simulated results with a number ofphysiological studies reported by other researchers,namely with the experimental human body temperatures

obtained by Raven and Horvath [15] for a transient coldexposure on eleven male. The experimental results ofRaven and Horvath [15] were also used by Fiala et al.[16] to validate their 15 segments thermoregulationmodel. In order to improve its capabilities of predictinghuman thermophysiological responses to cold air, thismodel has been recently updated by Lichtenbelt et al.[17] through the incorporation of individualised personcharacteristics. A 16 segments thermoregulation modelhas been used by Yokoyama et al. [18] for evaluating thehuman adaptability to outside coastal area activities inthe winter season. A slightly good agreement betweenthe calculated and the measured one was reported.

However, none of the preceding numerical studies isdedicated to the thermophysiological response of thehuman being while working in cold thermal environmentssuch as those frequently occurring inside freezingchambers, refrigerating cold stores or low temperaturemanufacturing workplaces.

The main objective of this work is the evaluation of thereal cold thermal stress supported by individuals workingin Portuguese cold industry and the achievement ofuseful guidelines for improvements in terms of protectingclothing and of times of exposure and recovering. Thetransient evolutions of skin, rectal, intestine,hypothalamus and lungs temperatures reached by the

human body under real circumstances are compared withsituations where the recommended clothing or exposureand recovering times are considered. Thethermophysiological response of men is obtained with anumerical procedure based on the Stolwijk [19]thermoregulation model, improved with recent knowledgefounded in the literature. This enhanced 89-node modelconsiders the human body divided in 22 segments(Raimundo and Figueiredo [20]).

2. Cold industrial workplaces

The measurements include 32 industrial units,corresponding to 79 different working indoors coldspaces, from 6 activity sectors (fish, meat, milk foodproduction, food conservation, food distribution andpharmaceutical distribution). These work environmentswere allocated to three typical exposure categoriescorresponding to 18 freezing chambers, 31 refrigeratingcold stores and 30 controlled air temperaturemanufacturing workplaces. The number of peopleexposed to cold thermal environments in the 32 industrialunits was 1151. The field measurements shown here is aselection from the results of Oliveira et al. [12], wherethey are revealed in a more detailed form.

After an appropriate stabilization period, themeasurement of the physical parameters was donesimultaneously during a 1 h evaluation and was carried

out according to ISO 7726 [21]. The field evaluationswere performed with mobile and portable apparatus thatincorporates three arrays of sensors, placed at 0.1, 1.1and 1.7 m above the floor. These levels correspond tothe ankles, abdomen and head heights for a standingworker. The physical parameters recorded are the air

temperature (Ta), mean radiant temperature (Tmr), relativehumidity (RH) and air velocity (va ).

The worker activity level (M) was estimated accordingto ISO 8996 [22], using the methods of level II ofaccuracy. The standard procedure consisted of addingthe metabolic rates corresponding to the posture, thetype of work, the body motion related to the work speedand the basal metabolic rate, for each single activity.Whenever we got permission from the workers, themetabolic rate estimation was based on heart ratemeasurements. Good agreement between bothestimation methodologies was achieved.

The intrinsic thermal insulation of the ensemble (Icl)was calculated following ISO 9920 [23] by adding thevalues corresponding to each garment. For this purpose,a questionnaire with a set of figures representing differenttypes of garments was used and the workers were askedto identify the garments worn. To assess possibleinaccuracies, the thermal insulation of cold protectiveclothing was measured with a thermal manikin in aclimate chamber (Oliveira et al. [24]). The results showthat the estimated values for 21 typical indoor garmentswere usually overestimated, but with no significantdifferences.

The field measured parameters for the three cold

spaces considered are summed up in Table 1, where theaverage and corresponding standard deviation of airtemperature (Ta , STa), mean radiant temperature (Tmr ,STmr), relative humidity (RH, SRH) and air velocity (va ,Sva) is shown. Workers average and standard deviationof the estimated values for the metabolic rate (M, SM),clothing thermal insulation (Icl, SIcl), chronometer times ofexposure to cold (ET, SET) and recovery in warm (RT,SRT) are presented in Table 2.

As it might be expected, the results for M show thathigher physical activities are generally found in thefreezing chambers and the highest values occur in themeat industry. The clothing insulation seems to be much

more related to the air temperature, with the highestvalues obtained in the freezing chambers, where theglobal Iclvary from 1.18 to 1.80 clo.

As stated in Oliveira et al. [12], a significantpercentage of freezing chambers workers are repeatedlyexposed to extreme conditions with insufficient clothinginsulation. In the majority of situations, the workersclothing ensemble does not provide the minimumrequired insulation, i.e. IclIREQmin. Surprisingly, for theother two cases of work in a cold environment(refrigerating cold stores and manufacturing workplaces),the most frequent scenario is characterized by the use ofensembles with an insulation value greater than the

recommended (Icl IREQneutral). Therefore, furtherattention must be given to these issues in order to



3/11

carefully adapt the choice of clothing according to thework environment, times of exposure and person activity.

Table 1. Measured physical characteristics of the three working indoors colds spaces.

Ta STa Tmr STmr RH SRH va Sva

Work environment C C C C % % m/s m/s

Freezing chambers -19.3 1.5 -22.8 2.9 86 12 0.53 0.23

Refrigerating cold stores 4.5 2.1 2.4 2.2 85 9 0.29 0.31

Manufacturing workplaces 11.4 2.0 10.6 2.4 75 14 0.31 0.24

Table 2. Workers values for the three working indoors colds spaces.

M SM Icl SIcl ET SET RT SRT

Work environment met met clo clo h h h h

Freezing chambers 2.84 0.38 1.57 0.26 0.70 0.51 0.22 0.09

Refrigerating cold stores 2.64 0.32 1.24 0.23 0.88 1.02 Not recorded

Manufacturing workplaces 2.73 0.47 1.12 0.15 4.00 - - -

3. Human thermoregulation model

The thermoregulatory system of humans responds totheir environment dynamically, maintaining the body coretemperature within a narrow range. The understanding ofits principles and the development of mathematicalmodels for its representation has begun 50 years ago.During this time various multisegmental thermoregulationmodels for live human body have been appeared. Themost extensively used model was created by Stolwijk [19]and has been improved, refined and further developed byother authors, e.g. Konz et al. [25], Wissler [26],Huizenga et al. [14], Tanabe et al. [27]. Many of thesemodified models have been validated againstexperimental results and are good research tools for thesimulation of human body response to different thermalenvironments.

To obtain the results presented in this study, a

computer program implemented by the authors [20] isused for the simulation of heat and mass transfer andthermophysiological response of a man working indoorsthe colds spaces under analysis. The program iscomposed by six modules, for the calculation of: ( i) manthermophysiological response, (ii) heat and watertransport through the clothing, (iii) heat (by conduction,convection and radiation) and mass exchange betweenthe external surface of clothing (or skin) and theenvironment and surroundings, (iv) thermal comfortanalysis and quantification, (v) start and evolution of skininjuries (pain and burn) and (vi) detection of specificincidents within the man. Due to its interdependency, all

modules are run iteratively in each time step until aspecific convergence criterion is reached. Also, the

iterative process is convergent only if the time step issmall enough to assure stabilization.

The module for simulation of man thermophysiologicalresponse is based on the Stolwijk [19] thermoregulationmodel, improved with recent knowledge founded in theliterature. This enhanced 89-node model considers the

human body divided in 22 segments (face, scalp, neck,chest, abdomen, upper back, lower back, pelvis, leftshoulder, right shoulder, left arm, right arm, left forearm,right forearm, left hand, right hand, left thigh, right thigh,left leg, right leg, left foot and right foot). Each bodysegment is composed of 4 layers (core, muscle, fat andskin) and the 89th node is the central bloodcompartment. The model was implemented for anaverage man with 74.43 kg of body weight, 1.72 m ofheight and 14 % of body fat (1.869 m2 of skin). For anindividual with other anthropometric data, theappropriated coefficients are proportionally changed infunction of its body weight and skin area. The temporal

evolution of temperature (T ) in each node i of the humanbody (except blood) is obtained by the following generalequation:

88

,

1

1

2 1 2

ii i j i i i i

j

i i i i i i

i i i i

Tm cp Q MB Wi We

t

Sh B Resp Persp Sw Cond

Cond Conv Rad Rad

=

= + + +

+

where miand cpiare the mass and specific heat of thenode, respectively. The term Qj,i represents the heattransferred through the tissues within individual segments

by conduction. The rate of heat production is expressedby the result of the basal metabolism (MBi), the internal



4/11

work (Wii), the external work or motion (Wei) and theshivering (Shi), with the heat production by work andshivering occurring only in the muscle layer. Theexchange of heat between all local layers and the centralblood compartment via blood circulation is taken intoaccount by term Bi. The loss of heat by respiration

(Respi) is compounded by a sensible and a latent partand is supposed to occur only at the core of chestsegment (lungs). The evaporative heat loss at skinsurface has two components, perspiration (Perspi) andsweating (Swi), both functions of clothing properties, manthermal status, ambient water vapour pressure andevaporative transfer characteristics at clothing externalsurface (or skin for a naked segment). At the skin layersurface, heat is lost by conduction to clothing (Cond1i)and by direct contact of naked parts with externalsurfaces (Cond2i). Also for naked skin layers, the transferof heat can occur by convection with the ambient air(Convi), by infra-red radiation with known temperature

surroundings (Rad1i) and by a radiation flux from aspecific source (Rad2i). For clothed skin body parts, thecomponents Cond2i, Convi, Rad1i and Rad2i are notaccounted at skin layer but at external surface of thecorresponding exterior clothing. The heat balance on thecentral blood compartment is

88b

b b

1

i

i

Tm cp B

t=

=

where mb and cpb are the mass and specific heat ofhuman body blood, respectively. The modelling of bloodflow heat transfer with each node takes into account theblood flow rate, the counter-current heat exchange

between arteries and vanes, the vasodilatation and thevasoconstriction in this layer. The controlling systemreceives the instantaneous values of temperature andtemperature change rate on all layers. The person overallthermal status is evaluated by the appropriate integrationof these warm and cold signals. The control systemtranslates this information into commands. These ordersare distributed to the appropriate layers where they areused for local modulation of each internal componentpresented in the equations. More detailed informationabout Stolwijk base models can be obtained in theprevious referred bibliography.

The simulation of heat and water transport throughclothing is a very complicated task due to the complexphenomena involved (e.g. Ghenaim et al. [28], Bouskill etal. [29], Yi et al. [30]). In the present state, they areaccounted using the simplified model described inHavenith et al. [31] and ISO 9920 [23]. This model isbased on local values for the specific human bodysegment of skin area (Ask), of local clothing insulation (Icl)and vapours permeation efficiency (ivp), of saturatevapour pressure on the skin surface, of temperature onskin (Tsk) and on external surface of clothing (Tcl) and ofambient air temperature (Ta), velocity (va) and relativehumidity (RH). As stated in ISO/TR 11079 [4], Holmr et

al. [32], Havenith and Nilsson [33], Oliveira et al. [24],between others, the ventilation of the clothing system dueto the human motion decreases clothing insulation

effectiveness and this effect must be taken into account.In order to consider the diminution of insulation due tobody movements, the Icl value at each human bodysegment is multiplied by a particular reduction factor ficl,related with the activity level Mby a simplified relation.

The convective and radiative heat fluxes calculation is

done by automatic process. The convective heat transferphenomena is simulated using empirical relations derivedfrom thermal manikin experiments by Quintela et al. [34]for natural convection and from Havenith et al. [31] andISO 7730 [35] for forced convection. The effectiveradiation areas and Gebhart absorption factors, neededfor the calculus of radiation components on each humanbody segment, are determined automatically by theprogram by approximated relations. These relations wereprevious established using a radiation programimplemented by Raimundo et al. [36] and are valid forman standing, sitting, lying with chest up and lying withchest down postures.

The module for prediction of thermal comfort is basedon the standard ISO 7730 [35], probably the most widelyused norm for the quantification of the human thermalsensation for moderate thermal environments. However,the thermal environment on the working indoors coldspaces is far from the validity of the norm ISO 7730(moderate thermal conditions). Then, this analysis is notvalid for evaluating the thermal comfort (or discomfort) ofpersons working under this conditions. Also, the modulesfor the simulation of the start and evolution of skin injuries(pain and burn) and for the detection of specific incidentswithin the man are not needed for the present study.

In order to achieve confidence in the predictive abilitiesof the program and its physical and mathematicalalgorithms, a wide-range of validation work has beendone. The extensive conditions tested included differenttypes of environments (cold, cool, neutral, warm and hot),of exposures (uniform and sudden change of conditions),of exercise intensities (0.8 to 4 met) and of worn clothing.The experimental results used for validation include coretemperatures (tympanic, esophageal, intestinal andrectal), average and local skin temperatures (head, trunk,arm, hand, leg, foot, etc.) and mean body temperature aswell as metabolic heat production and evaporative heatloss. The accurate predictions of the program during the

validation tests are an excellent indication of its capacityto reproduce human body thermoregulatory responsesover the range of climatic conditions investigated.Unfortunately, on the extensive literature checked, theexperimental data found related to physiologicalresponses of human beings working on coldenvironments is not adequately detailed for validation ofthe program. Nevertheless, two model/experimentalcomparisons are provided in Figures 1 and 2, where coldenvironment conditions are included.

The comparisons between measured values for rectal,tympanic and skin average temperatures and predicteddata for rectal, hypothalamus and skin average

temperatures are shown in Figure 1. The experimentaldata represent averages for semi-nude, seated



5/11

individuals after 1 hour exposure to a range ofenvironment temperatures between 5 and 50 C, wereobtained for 44 persons by Wyndham et al. [37] and for86 individuals by Werner and Reents [38]. A reasonableagreement is shown.

Rectal

Skin average

Tympanic /Hypothalamus

0

20

40

60

80

100

120

140

160

180

22

24

26

28

30

32

34

36

38

40

0 10 20 30 40 50

Metabolism(W/m2)

Temperature(C)

Air and radiant temperature (C)

Fig. 1. Comparison of measured (points) and predicted (lines)values for rectal, tympanic (exp.) / hypothalamus (calc.) andskin average temperatures and metabolism heat production, for1 hour exposure with Ta= Tmr, va= 0.2 m/s, RH= 50 %, Icl= 0.1clo and M= 0.8 met.

In order to check the capabilities of the program forsimulation of sudden alterations on environmentconditions, a large range of comparisons were made forabrupt changes from hot to cold and from cold to hot. Asan example, in Figure 2 shows a comparison betweensome of the measured and predicted valuesrepresentative of the human thermo-physiological

response to a rapid change from a warm environment toa cold environment, in still air. The experimental data wasobtained for 11 male by Raven and Horvath [39] and for8 male by Savourey and Bittel [40]. The subjects woreonly shorts and rested in a supine position on a nylon-strip bed that was wheeled from one chamber to another.The slightly good agreement achieved indicates aninteresting capacity of the program to predict the thermo-physiological reaction of human body in dynamicconditions.

4. Results and discussion

Three different typical working in cold spaces were

selected corresponding to (i) freezing chambers, (ii)refrigerating cold stores and (iii) cool controlled airtemperature manufacturing workplaces. For each ofthem, three different cases are analyzed: the real

situation; one ideal scenario, with the human beingwearing proper clothing for the real exposure and recovertimes; and other ideal case, with the worker following thetimes of exposure and of recover recommend for the realclothing insulation that it wears.

9

14

19

24

29

34

39

0 30 60 90 120 150

Temperature(C)

Time (min)

Forehead Chest Arms Finger ToeForehead Chest Arms Hands Feet

Fig. 2. Comparison of measured (points) and predicted (lines)values for rectal, skin average and skin segmentstemperatures, for sudden ambient temperature changes from awarm environment (Ta = Tmr = 28.5 C, RH = 45%) to a coldenvironment (Ta= Tmr= 4.7 C, RH= 70%), with va= 0.1 m/s,Icl= 0.1 clo and M= 0.8 met.

Freezing chambers

The freezing chambers are characterised by the followingaverage values for Ta= - 19.3 C, Tmr= -22.8 C, RH =86 % and va= 0.53 m/s. The thermal characteristics ofthe workers recovering space are Ta = + 22.1 C,

Tmr= + 19.9 C, RH = 60 % and va = 0.49 m/s. Thephysical and physiological parameters related with theworker are shown in Table 3 for the three differentsituations.

In Figures 3, 4 and 5, the temporal evolution of humanbody temperatures for the three differentthermophysiological conditions detailed in Table 3 isrepresented. In Figures a) temperatures on lungs,rectum, intestine and hypothalamus are shown and inFigures b) average skin temperatures for all body, ofhead, of central body, of upper members and of lowermembers are revealed. Starting from thermal neutrality,the exposure to cold begins at instant zero in time axis

Table 3. Parameters for three different possibilities of working in a freezing chamber.

Freezing chamber Exposure Recover

M Icl ET M Icl RT

Case under analysis met clo h met clo h

1- Real situation 2.84 1.57 0.70 1.60 1.18 0.22

2- Proper clothing 2.84 1.99 0.70 1.60 1.18 0.22

3- Recommend times 2.84 1.57 0.25 1.60 1.18 0.25



6/11

34

35

36

37

38

39

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Tempera

ture(C)

Time (h)

Lu ngs In test in e Rectal Hypothalamus

20

24

28

32

36

40

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Averageskintemperature(C)

Time (h)

Head Upper members Skin avrg

Central body Lower members

Fig 3. Human body temperatures obtained for the real situation of a man working in a freezing chamber:

a) core temperatures; b) average skin temperatures.

34

35

36

37

38

39

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Temperature(C)

Time (h)

Lungs Intestine Rectal Hypothalamus

20

24

28

32

36

40

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Time (h)



Fig 4. Human body temperatures obtained for the situation of a man working in a freezing chamber wearing proper clothing:


34

35

36

37

38

39

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Tem

perature(C)

Time (h)


20

24

28

32

36

40

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Averageskin

temperature(C)

Time (h)



Fig 5. Man working in a freezing chamber following the times of exposure and of recover recommend for the real clothinginsulation that it wears: a) core temperatures; b) average skin temperatures.

b)a)

a)

a)

b)

b)



7/11

In comparison with the real situation (Fig. 3), thewearing of more proper clothing thermal insulation (Fig.4) avoids the decrease of body temperatures too faraway from the thermal neutrality. Alternatively, as it canbe seen on Fig. 5, for a situation with insufficient clothing

insulation, it is also possible to avoid the human bodycooling if shorter times of exposure at the coldenvironment and greater times of recovering in a warmenvironment are adopted.

As far as the core temperatures are concerned, therectal temperature has always the greatest value and thelungs the shortest. Also, in contrast with rectal, the lungstemperature presents a strong sensibility to theenvironment temperature. This fact is related to theintake of air by respiration. The head and central bodyskin temperatures are always above of average skintemperature and the upper and lower members skin

temperature are below.The situation with proper clothing thermal insulation

ensures a more uniform temperature range betweendifferent human body parts. Also, it addresses thetemperature values closer to thermal neutrality. Thesefacts suggest that this is the recommended situation.However, protective clothing with insulating values above2 clo restricts worker movements, therefore not practical.

Refrigerating cold stores

The refrigerating cold stores analysed are characterisedby the following average values for Ta= 4.5 C, Tmr= 2.4C, RH = 85 % and va= 0.29 m/s. The recovering periodwas not recorded. But, as it can be seen later, itsexistence is not important. Consequently, its duration issupposed to be 0.12 h and the thermal characteristics ofthe recovering space are assumed equal as for theprevious case: Ta= 22.1 C, Tmr= 19.9 C, RH= 60 %and va = 0.49 m/s. The physical and physiologicalparameters related with the worker are shown in Table 4for the two different situations of interest.

In Figures 6 and 7, the temporal evolution of humanbody temperatures for the three differentthermophysiological conditions detailed in Table 4 isrepresented. In Figures a) temperatures on lungs,

rectum, intestine and hypothalamus are shown and inFigures b) average skin temperatures for all body, of

head, of central body, of upper members and of lowermembers are revealed. Starting from thermal neutrality,the exposure to cold begins at instant zero in time axis

Comparing the real present situation of working in arefrigerating cold store (Fig. 6) with the previous one of

working in a freezing chamber (Fig. 3), a clear distinctioncan be pointed out. Now, the workers wear ensembleswith insulation higher than the required value,representing a certain risk of hyperthermia withprogressive exposure. As can be see in Figure 6, theexistence of recovering periods is not important and, ifthe assumed conditions were used, they increase theexcess of heat stored on the human body.

The results shown in Figure 7 are for the case of theworker wearing a lighter suit than in real situationpresented in Fig. 6. It is evident that instead of wearingan ensemble with a global insulation Icl = 1.24 clo, it is

recommended the use of clothing insulation with an Iclvalue around 1 clo or less. The effect of the decrease ofclothing insulation has a greater influence on the coretemperatures, namely on lungs, than on the skintemperatures. However, this fact doesnt warrant animprovement of thermal comfort.

Cool manufacturing workplaces

The cool controlled air temperature manufacturingworkplaces are characterised by the following averagevalues for Ta= + 11.4 C, Tmr = + 10.6 C, RH = 75 %and va = 0.31 m/s. In the field measurements norecovering periods were reported. The results presented

next in this work demonstrate that they are not needed.The physical and physiological parameters related withthe worker are shown in Table 5 for the two differentsituations under analysis.

In Figures 8 and 9, the temporal evolution of humanbody temperatures for the three differentthermophysiological conditions detailed in Table 5 isrepresented. In Figures a) temperatures on lungs,rectum, intestine and hypothalamus are shown and inFigures b) average skin temperatures for all body, ofhead, of central body, of upper members and of lowermembers are revealed. Starting from thermal neutrality,

the exposure to cold begins at instant zero in time axis.

Table 4. Parameters for two different possibilities of working in a refrigerating cold store.

Cold stores Exposure Recover

M Icl ET M Icl RT


1- Real situation 2.64 1.24 0.88 1.60 0.99 0.12

2- Proper clothing 2.64 1.01 4.0 - - -



8/11

34

35

36

37

38

39

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Tempera

ture(C)

Time (h)


20

24

28

32

36

40

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Averageskintemp

erature(C)

Time (h)



Fig 6. Human body temperatures obtained for the real situation of a man working in a refrigerating cold store:


34

35

36

37

38

39

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Temperature(C)

Time (h)

Lungs In te st in e Re ct al H yp ot hal am u s

20

24

28

32

36

40

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Time (h)



Fig 7. Human body temperatures obtained for the situation of a man working in a refrigerating cold store wearing proper clothing:


As reported in Fig. 8, the real situation of working in acool manufacturing workplace is characterized by thewearing of ensembles with insulation higher than therequired value, representing an effective risk ofhyperthermia, namely for long exposures. Comparing tothe real situation, where the worker wears an ensemble

with a global insulation Icl = 1.12 clo (Fig. 8), with themore appropriate case shown in Fig. 9, the advantage ofthe use of clothes with global insulation values around

0.83 clo or even less is evident. The decrease of clothinginsulation is essentially reflected on core temperatures,with only a small influence in skin temperatures. It is alsoof notice the existence of an initial period of time, around1 h for the real situation and 1.5 h for the use of properclothing, with a notorious decrease of temperature in all

human body parts and layers.

Table 5. Parameters for two different possibilities of working in cool manufacturing workplaces.

Cool manufacturing workplaces Exposure Recover

M Icl ET M Icl RT


1- Real situation 2.73 1.12 4.0 - - -

2- Proper clothing 2.73 0.83 4.0 - - -

b)a)

a) b)



9/11

34

35

36

37

38

39

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Temperature(C)

Time (h)


20

24

28

32

36

40

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Time (h)



Fig 8. Human body temperatures obtained for the real situation of a man working in cool manufacturing workplaces:


34

35

36

37

38

39

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Temperature(C)

Time (h)

Lungs In te st in e R ect al H ypo th alam u s

20

24

28

32

36

40

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Time (h)



Fig 9. Human body temperatures obtained for the situation of a man working in a cool manufacturing workplaces wearing proper

clothing: a) core temperatures; b) average skin temperatures.

5. Conclusions

The results presented in this work demonstrate that asignificant percentage of the people working in indoorscold environments are repeatedly exposed to extremeconditions with insufficient clothing insulation (freezingchambers) or wear clothing with insulation values above

the recommended ones (refrigerating cold stores andcool controlled air temperature manufacturingworkplaces). The freezing chambers represent the mostsevere case, where the environment low temperaturesassociated with prolonged exposures and insufficientclothing insulation can promote cold thermal stress.Though less severe, in the other two cases the oppositesituation occurs, since the used clothing ensembleprovides more insulation than it is required. From a globalpoint of view, it is clear that the clothing ensembles wornby the people working in these cold environments areinadequate.

With the use of a mathematical multi-node

thermoregulation model, it is suggested the use ofclothing with more appropriate thermal insulation values.

Namely, for working in cool controlled air temperaturemanufacturing workplaces a global clothing insulation Icl0.8 clo is recommended, instead of Icl= 1.12 clo. Forthe workers of the refrigerating cold stores a value ofIcl1 clo is preferable, in place of Icl= 1.24 clo. Finally,for working in freezing chambers an ensemble withIcl2clo is suggested, instead of Icl= 1.57 clo. Alternatively, if

for a particular task clothes with Icl2 clo are to muchrestrictive of worker movements, it is possible to maintainthe use of ensembles with Icl= 1.57 clo if the exposuretimes are reduced from 0.7 h to around 0.25 h and therecovered times are kept on 0.22 h or slightly increasedto 0.25 h.

As a final remark, the cold thermal stress of humansworking in indoors cold environments cant be completelycharacterized using mathematical thermoregulationmodels. Methodologies focused on subjective analysisshould be also considered. Thus, the work herepresented must be complemented with field evaluations,based on workers response to appropriate

questionnaires.

b)a)

a) b)



10/11

References

[1] ISO 12894 (2001). Ergonomics of the thermalenvironment Medical supervision of individualsexposed to extreme hot or cold environments, FirstEdition, ISO, Genve, Switzerland.

[2] Siple PA, Passel CF (1945). Measurements of dryatmospheric cooling in subfreezing temperatures.Proceedings of the American Philosophical Society, 89,pp. 177-199.

[3] Holmr I (1984). Required clothing insulation (IREQ)as an analytical index of cold stress. ASHRAETransactions, 90, pp. 1116 1128.

[4] ISO/TR 11079 (1993). Evaluation of ColdEnvironments Determination of Required ClothingInsulation (IREQ). Technical Report, First edition, ISO,Genve, Switzerland.

[5] Holmr I (1993). Work in the cold: Review of methods

for assessment of cold exposure. Int. Arch. Occup.Environ. Health, 65, pp. 147-155.

[6] ISO 11399 (1995). Ergonomics of the thermalenvironment Principles and application of relevantInternational Standards, First edition, ISO, Genve,Switzerland.

[7] Gavhed D, Holmr I (1998). Thermal responses atthree low ambient temperatures: Validation of theduration limited exposure index. Int. Journal of IndustrialErgonomics, 21, pp. 465 474.

[8] Griefahn B (2000). Limits and possibilities to improvethe IREQ cold stress model (ISO/TR 11079). A validation

study in the field. Applied Ergonomics, 31, pp. 423 431.[9] Tochihara Y (1998). Work in artificially coldenvironments. In: Holmr I and Kuklane K (eds),International Symposium on Problems With Cold Work,National Institute for Working Life, 16-20 November1997, Stockholm, Sweden, pp. 13-15.

[10] Kim T, Fujita M, Hashiguchi N, Tochihara Y (2005).Physiological responses and performance duringexposure to severe cold. In: Holmr I, Kuklane K andGao G (eds), 11th International Conference onEnvironmental Ergonomics, ICEE 2005, 22-26 May,Ystad, Sweden, pp. 270-273.

[11] Nielsen R (1998). Characteristics of cold workplacesin Denmark. In: Holmr I and Kuklane K (eds),International Symposium on Problems with Cold Work.National Institute for Working Life, 16-20 November1997, Stockholm, Sweden, pp. 16-18.

[12] Oliveira AV, Gaspar AR, Quintela DA (2007).Occupational exposure to cold thermal environments: afield study in Portugal. Eur. J. Applied Physiol, DOI10.1007/s00421-007-0630-5.

[13] Xu X, Werner J (1997). A dynamic model of thehuman / clothing / environment-system. J. PhysiologicalAnthropology, Applied Human Science, 16 (2), pp. 61-75.

[14] Huizenga C, Hui Z, Arens E (2001). A model ofhuman physiology and comfort for assessing complex

thermal environments, Building and Environment, 36, pp.691-699.

[15] Raven PR, Horvath SM (1970). Variability ofphysiological parameters of unacclimatized males duringa two-hour cold stress of 5 C, International J.Biometeorology, 14 (3), pp. 309-320.

[16] Fiala D, Lomas KJ,Stohrer M (2001). Computerprediction of human thermoregulatory and temperatureresponses to a wide range of environmental conditions,International J. Biometeorology, 45, pp. 143-159.

[17] van Marken Lichtenbelt WD, Frijns AJH, van OoijenMJ, Fiala D, Kester AM, van Steenhoven AA (2007).Validation of an individualised model of humanthermoregulation for predicting responses to cold air,International J. Biometeorology, 51, pp. 169-179.

[18] Yokoyama S, Yamamoto N, Baba H, Shibayama D,Atsumi Y, Kioka S, Ishizawa T, Ozaki H, Ogawa W(2005). Prediction computer program of whole body

temperatures and heat fluxes and its application toevaluate human thermal responses, InternationalConference on Environmental Ergonomics, 22-26 May,Ystad, Sweden.

[19] Stolwijk JAJ (1971). A mathematical model ofphysiological temperature regulation in man. NASAcontractor report CR-1855. NASA, Washington DC.

[20] Raimundo AM, Figueiredo AR (2006). Humanthermophysiological response to high intensity radiationfluxes near a forest fire line, Proceedings of ICFFR 2006(5th International Conference on Forest Fire Research),Figueira da Foz, Portugal, pp. S145 (1-16).

[21] ISO 7726 (1998). Ergonomics of the thermalenvironment Instruments for measuring physicalquantities, Second edition, ISO, Genve, Switzerland.

[22] ISO 8896 (1990). Ergonomic Determination of themetabolic heat production, First edition, ISO, Genve,Switzerland.

[23] ISO 9920 (1995). Ergonomics of the thermalenvironment Estimation of the thermal insulation andevaporative resistance of a clothing ensemble, Firstedition, ISO, Genve, Switzerland.

[24] Oliveira AVM, Gaspar AR, Quintela DA (2005).Thermal insulation of cold protective clothing: static anddynamic measurements with a movable thermal manikin.Holmr I, Kuklane K, Gao G eds, ICEE 2005 - 11 thInternational conference on environmental ergonomics,Ystad, pp. 99-102.

[25] Konz S, Hwang C, Dhiman B, Duncan J, Masud A(1977). An experimental validation of mathematicalsimulation of human thermoregulation, Computers inBiology and Medicine, 7, pp. 71-82.

[26] Wissler EH (1985). Mathematical simulation ofhuman thermal behaviour using whole body models, In:Shitzer A, Eberhart RC (eds) Heat transfer in medicineand biology analysis and applications. Plenum, NewYork London, pp. 325-373.



11/11

[27] Tanabe S, Kobayashi K, Nakano J, Ozeki Y, KonishiM (2002). Evaluation of thermal comfort using combinedmulti-node thermoregulation (65MN) and radiationmodels and computational fluid dynamics (CFD), Energyand Buildings, 34, pp. 637-646.

[28] Ghenaim A, Achari AE, Amar SB, Caze C (2000).

The dynamics of heat and moisture transportationthrough textiles, Sixth Triennial International Symposiumon Fluid Control, Measurement and Visualization(FLUCOME 2000), 13-17 August, Sherbrook, Canada.

[29] Bouskill LM, Havenith G, Kuklane K, Parsons KC,Withey ER (2002). Relationship between clothingventilation and thermal insulation, AIHA Journal, 63, pp.262-268.

[30] Yi L, Fengzhi L, Yingxi L, Zhongxuan L (2004). Anintegrated model for simulating interactive thermalprocesses in human-clothing system, Journal of ThermalBiology, 29, pp. 567-575.

[31] Havenith G, Holmr I, Parsons K (2002). Personalfactors in thermal comfort assessment: clothingproperties and metabolic heat production. Energy andBuildings, 34, pp. 581-591.

[32] Holmr I, Nilsson H, Havenith G, Parsons K (1999).Clothing convective heat exchange - proposal forimproved prediction in standards and models, Annals ofOccupational Hygiene, 43 (5), pp. 329-337.

[33] Havenith G, Nilsson H (2004). Correction of clothinginsulation for movement and wind effects, a meta-analysis, European J. of Applied Physiology, 92, pp. 636-640.

[34] Quintela DA, Gaspar AR, Borges C (2004). Analysisof sensible heat exchanges from a thermal manikin.European J. of Applied Physiology, 92 (6), pp. 663-668.

[35] ISO 7730 (1994). Moderate thermal environments -determination of PMV and PPD indices and specificationof the conditions for thermal comfort, ISO, Genve,

Switzerland.[36] Raimundo AM, Gaspar AR, Quintela DA (2004).Numerical modelling of radiative exchanges between thehuman body and surrounding surfaces. Climamed 2004 -1st mediterranean congress of climatization, paper 8/1,Lisbon, Portugal, 16-17 of April.

[37] Wyndham C, Ward J, Strydom N, Morrison J,Williams C, Bredell G, Peter J, von Rahden M,Holdsworth L, van Graan C, van Rensburg A, Munro A(1964). Physiological reactions of caucasian and bantumales in acute exposure to cold, J. of AppliedPhysiology, 19, pp. 538-592.

[38] Werner J, Reents T (1980). A contribution to thetopography of temperature regulation in man, EuropeanJ. of Applied Physiology, 45, pp. 87-94.

[39] Raven PR, Horvath SM (1970). Variability ofphysiological parameters of unacclimatized males duringa two-hour cold stress of 5 C, International J. ofBiometeorology, 14 (3), pp. 309-320.

[40] Savourey G, Bittel J (1998). Thermoregulatorychanges in the cold induced by physical training inhumans, European J. of Applied Physiology, 78, pp. 379-384.


14.Raimundo Portugal

Documents

Transcript of 14.Raimundo Portugal