The effect of clothing insulation on the thermophysiological comfort of workers in artificial cold environment

Abstract

The present study deals with the effect of the clothing insulation on the thermophysiological comfort of workers in artificial cold environment. Different types of artificial cold environment, related to food industry, have been identified, together with the activity of the workers. For the assessment of the cold exposure and the clothing insulation needed for the state of thermophysiological comfort, the Required Clothing Insulation (IREQ) index was calculated. On the basis of comparison with the used level of clothing insulation (2.5 clo), the Duration Limited Exposure (DLE) index and Recovery Time (RT) were determined. Different conditions of the warm environment, where the workers had to recover from the cold exposure, were also tested: temperature of the environment, clothing insulation and activity. The results obtained suggest strategies for management of the cold exposure of workers in the food industry, related to their activity, clothing insulation and environmental conditions.

Full text

Industria
Textila
ISSN 1222–5347
5/2016
Recunoscutã în România, în domeniul ªtiinþelor inginereºti, de cãtre
Consiliul Naþional al Cercetãrii ªtiinþifice din Învãþãmântul Superior
(C.N.C.S.I.S.), în grupa A /
Aknowledged in Romania, in the engineering sciences domain,
by the National Council of the Scientific Research from the Higher Education
(CNCSIS), in group A
COLEGIUL
DE REDACTIE:
Dr. ing. CARMEN GHIŢULEASA
cerc. şt. pr. I – DIRECTOR GENERAL
Institutul Naţional de Cercetare-Dezvoltare
pentru Textile şi Pielărie – Bucureşti
Dr. ing. EMILIA VISILEANU
cerc. şt. pr. I – EDITOR ŞEF
Institutul Naţional de Cercetare-Dezvoltare
pentru Textile şi Pielărie – Bucureşt
Prof. dr. GELU ONOSE
cerc. şt. pr. I
Universitatea de Medicină şi Farmacie
„Carol Davila“ – Bucureşti
Prof. dr. ing. ERHAN ÖNER
Marmara University – Turcia
Assistant prof. dr. AMINODDIN HAJI
PhD, MSc, BSc, Textile Chemistry
and Fiber Science
Textile and Art Department
Islamic Azad University, Birjand Branch
Birjand – Iran
Prof. dr. ing. PADMA S. VANKAR
Facility for Ecological and Analytical Testing
Indian Institute of Technology – India
Prof. univ. dr. ing. CARMEN LOGHIN
Universitatea Tehnică „Ghe. Asachi“ – Iaşi
Ing. MARIANA VOICU
Ministerul Economiei
Prof. univ. dr. MARGARETA STELEA FLORESCU
Academia de Studii Economice – Bucureşti
Prof. ing. ARISTIDE DODU
cerc. şt. pr. I
Membru de onoare al Academiei de Ştiinţe
Tehnice din România
C
onf. uni
v. d r. ing. MARIANA URSACHE
Decan
Facultatea de Textile-Pielărie
şi Management Industrial
Universitatea Tehnică „Ghe. Asachi“ – Iaşi
Prof. dr. LIU JIHONG
Jiangnan University – China
IZABELA JASIŃSKA
Analiza descompunerii termice a fibrelor naturale selectate pe baza
evaluării vizuale în timpul procesului de încălzire 287–291
HALIL IBRAHIM CELIK
Dezvoltarea unui sistem de control vizual pentru inspecţia bobinelor
de fire 292–296
HUSEYIN GAZI TURKSOY, SINEM BILGIN
Eficacitatea ecranării electromagnetice a tricoturilor spațiale hibride 297–301
RADOSTINA A. ANGELOVA
Efectul izolației termice a îmbrăcămintei asupra confortului
termofiziologic al lucrătorilor din mediul rece artificial 302–307
MADALINA IGNAT, AURORA PETICA, CARMEN GAIDAU,
IULIANA DUMITRESCU, LILIOARA SURDU, LAURENTIU DINCA,
JIANZHONG MA, JIANJING GAO
Nanomateriale fotocatalitice pe bază de TiO2dopat pentru articole
de îmbrăcăminte din piele şi tapiţerie cu proprietăţi de autocurăţare 308–313
LILIOARA SURDU, IOAN SURDU, IOAN RAZVAN RADULESCU
Cercetări pentru realizarea de textile multifuncţionale prin tehnologia
cu plasmă 314–321
AYTAÇ YILDIZ
Metoda fuzzy TOPSIS interval tip 2 şi metoda fuzzy TOPSIS în selectarea
furnizorului din industria de confecţii 322–332
ADNAN MAZARI, FUNDA BÜYÜK MAZARI, ENGİN AKÇAGÜN,
PAVEL KEJZLAR
Efectul vitezei de coasere asupra proprietăţilor fizice ale firelor
de cusut ale echipamentului de protecţie pentru pompieri 333–337
SIMONA TRIPA, SUNHILDE CUC, IOAN OANA
Avantaj comparativ aparent și competitivitate în industria de textile
şi de confecţii din România 338–344
M. STELA FLORESCU, FLORENTINA IVANOV
Globalizarea ca factor de influență asupra activității de C&D.
Cazul industriei textile din România 345–350
MOJTABA TARAN, MARYAM RAD, MEHRAN ALAVI
Sinteza biologică a nanoparticulelor de cupru prin utilizarea
Halomonas elongata IBRC-M 10214 351–356
Editatã în 6 nr./an, indexatã ºi recenzatã în:
Edited in 6 issues per year, indexed and abstracted in:
Science Citation Index Expanded (SciSearch®), Materials Science
Citation Index®, Journal Citation Reports/Science Edition, World Textile
Abstracts, Chemical Abstracts, VINITI, Scopus, Toga FIZ technik
ProQuest Central
RevistãcotatãISI ºi inclusãîn Master Journal List a Institutului pentru
ªtiinþa Informãrii din Philadelphia – S.U.A., începând cu vol. 58,
nr. 1/2007/
ISI rated magazine, included in the ISI Master Journal List of the Institute
of Science Information, Philadelphia, USA, starting with vol. 58, no. 1/2007
¸
˘
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2016, vol. 67, nr. 5
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2016, vol. 67, nr. 5
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IZABELA JASIŃSKA
HALIL IBRAHIM CELIK
HUSEYIN GAZI TURKSOY
SINEM BILGIN
RADOSTINA A. ANGELOVA
MADALINA IGNAT
AURORA PETICA
CARMEN GAIDAU
IULIANA DUMITRESCU
LILIOARA SURDU
LAURENTIU DINCA
JIANZHONG MA
JIANJING GAO
LILIOARA SURDU, IOAN SURDU
IOAN RAZVAN RADULESCU
AYTAÇ YILDIZ
ADNAN MAZARI
FUNDA BÜYÜK MAZARI
ENGİN AKÇAGÜN, PAVEL KEJZLAR
SIMONA TRIPA, SUNHILDE CUC
IOAN OANA
M. STELA FLORESCU
FLORENTINA IVANOV
MOJTABA TARAN
MARYAM RAD
MEHRAN ALAVI
287
292
297
302
308
314
322
333
338
345
351
Analysis of thermal decomposition of selected natural fibres on the basis of visual
changes during heating
Development of a machine vision system for yarn bobbin inspection
Electromagnetic shielding effectiveness of spacer knitted hybrid fabrics
The effect of clothing insulation on the thermophysiological comfort of workers in artificial
cold environment
Photocatlytic nanomaterials based on doped TiO
2
for leather garments and upholstery
with self-cleaning properties
Research for accomplishing multifunctional textiles with plasma technology
Interval type 2-fuzzy TOPSIS and fuzzy TOPSIS method in supplier selection in garment
industry
Effect of sewing speed on the physical properties of firefighter sewing threads
Revealed comparative advantage and competitiveness in Romanian Textile and Clothing
Industry
Globalization as a factor of influence on the R&D activity and the case of the textile
industry in Romania
Biological synthesis of copper nanoparticles by using Halomonas elongata IBRC-M 10214
EDITORIAL STAFF
Editor-in-chief: Dr. eng. Emilia Visileanu
Graphic designer: Florin Prisecaru
e-mail: industriatextila@certex.ro
Scientific reviewers for the papers published in this number :
Contents
Journal edited in colaboration with Editura AGIR, 118 Calea Victoriei, sector 1, Bucharest, tel./fax: 021-316.89.92; 021-316.89.93;
e-mail: editura@agir.ro, www.edituraagir.ro
CHENHONG LONG – Institute for Frontier Materials, GTP Research Deakin University, Australia
AMINODDIN HAJI – Department of Textile Engineering Birjand Branch Islamic Azad University, Iran
KAI MENG – College of Textile and Clothing Engineering, Soochow University, People’s Republic of China
LUCIAN GRAMA – „Petru Maior" University, Târgu-Mureş, Romania
CLAUDIA NICULESCU – The Research and Development National Institute for Textile and Leather, Romania
NICOLAE POP – Bucharest University of Economic Studies, Romania
TOADER RITA – Baia Mare North University, Romania

INTRODUCTION
Evaluation of properties of fibres during the process
of thermal decomposition is an important issue in the
process of analysis of textile products. Properties of
fibres such as the pace of change propagation in the
structure of a fibre caused by the increasing temper-
ature of the product or occurrence of the phe-
nomenon of thermal shrinkage of a fibre are relevant
when designing, e.g. processes of finishing treatment
of textiles or preservation processes. In laboratory
practice this is described as temperature of decom-
position (non-thermoplastic fibres) or melting, soften-
ing temperatures for thermo-plastic fibres as one of
the methods of identifying raw material, as well as
microscopic analysis, attempts to burn, chemical
methods or evaluation using FTIR spectrum – these
are methods listed in the Technical Report ISO/TR
11827:2012 [1–2].
Due to the preparation of new types of fibres, their
characteristics are presented as well as their dis similar -
ity towards other types of materials [3–5]. Moreover,
the already known techniques of fibre identification
undergo constant improvement, especially those
close ly related to each other. In their publication, the
authors elaborated an improved method of differen-
tial identification of flax and ramie fibres [6]. In the
publication the thermal properties and thermal dura-
bility of some natural fibres – cotton, ramie and wool
were investigated [7]. The TD-FTIR (temperature-
depen dent Fourier infrared transform) and differential
thermal analyses (TG-DSC) were used for determina -
tion of degradation and water loss of mentioned fibres.
Researchers found, that in the range of temperature
Analysis of thermal decomposition of selected natural fibres
on the basis of visual changes during heating
IZABELA JASIŃSKA
REZUMAT – ABSTRACT
Analiza descompunerii termice a fibrelor naturale selectate pe baza evaluării vizuale
în timpul procesului de încălzire
Proprietățile termice ale fibrelor liotrope sunt importante pentru procesele de tratare şi finisare (vopsire, stabilizare și
imprimare), precum și pentru procesele de întreținere. Schimbările care au avut loc în structura fibrelor sub influența
energiei termice au fost caracterizate prin modificarea culorii fibrelor (distrugerea termică a legăturilor chimice) și
contracția acestora. Analiza influenței energiei termice asupra rezistenţei structurii fibrelor, prezentate în manuscris, s-a
bazat pe evaluarea microscopică a modificărilor survenite în structura fibrei. Nouă tipuri de fibre au fost evaluate în acest
studiu. Acestea sunt: fibre celulozice naturale, fibre celulozice regenerate – fibre de viscoză şi proteice – soia și mătase.
Fibrele provin din surse diferite – mănunchiuri de fibre, semitort și fire. Pe baza testelor efectuate s-a stabilit că, pentru
fibrele de bumbac şi in, sursa materiei prime poate fi importantă în procesul de identificare, cu referire la descompunerea
termică. În ceea ce priveşte fibrele de viscoză (sau atunci când există probabilitatea apariției lor), s-a constatat că aceste
fibre sunt caracterizate printr-o contracție termică variată, în funcție de tipul lor. Se poate concluziona că fibrele cu
aceeași compoziție a materiei prime pot prezenta proprietăți diferite în ceea ce privește contracția termică și ritmul de
descompunere la o anumită temperatură, care ar trebui să fie luată în considerare în timpul procesului de tratare și
întreţinere la temperaturi mari.
Cuvinte-cheie: fibre celulozice, descompunerea termică a fibrelor, fibre non-termoplastice, contracția termică a fibrei
Analysis of thermal decomposition of selected natural fibres on the basis of visual changes during heating
Thermal properties of lytropic fibres are important for finishing treatment processes (dying, stabilization, and printing) as
well as for maintenance processes. The changes, which occurred in fibres structure under influence of thermal energy
were characterized by colour changing of fibres (thermal destruction of chemical bonds) and their shrinkage. The
analysis of influence of thermal energy to fibres structure fastness, presented in manuscript, was based on visual,
microscopic, assessment of changes occurred in fibre structure. The nine genres of fibres were evaluated in this study.
There were natural cellulose fibres, regenerated cellulose fibres – viscose and protein fibres- soya and silk. Fibres came
from different sources – loose fibres, roving, and yarn. Based on the performed tests, it was stated, that for cotton and
flax fibres, the source of raw material may be important during the process of identification with reference to thermal
decomposition. As for viscose fibres (or when there is likelihood of their occurrence), it was found that these fibres are
characterised by varied thermal shrinkage, depending on their type. It may be concluded that fibres of the same raw
material composition may present different properties in terms of thermal shrinkage and pace of decomposition at
certain temperature, which should be considered during the treatment process and maintenance using high
temperature.
Keywords: cellulose fibres, thermal decomposition of fibres, non- thermoplastic fibres, thermal shrinkage of fibre
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from 25°C to 210°C for all tested fibres thermal
degradation phenomenon was not detected. In
another research work the improvement of physical
and mechanical properties of hemp fibres and their
thermal resistance was investigated [8]. The large
group of research works in scope of properties, such
as thermal degradation, mechanical strength, for
new-investigated composites were undertaken. Most
of composites consisted of some natural fibre – sisal,
Boraussus fruit fibre, short curaua fibre and synthet-
ic polymer – PET, polypropylene [9–12]. As an exam-
ple, in the research work the thermogravimetric anal-
ysis (TGA) was used for determination thermal
decomposition of all composite components (recy-
cled PET, sisal fibres) [9]. It is important feature in
composite investigation, because the differences of
thermal degradation for composite substitutes made
decomposition process faster and easier. Mostly the
techniques of processing and image analysis sup-
ported by data mining technique are mostly used in
fibre identification process [13–15].
Summarising the above literature review, it can be
stated that in order to differentiate textile products of
natural origin and analysis of composites consisted
of natural and synthetic fibres, there is a wide range
of methods of evaluation and identification applied,
such as TD-FTIR, TGA or TG-DSC. The microscopic
evaluation of fibres is used rather in case of investi-
gation of image analysis-based identification tech-
niques or in form of SEM images. There were not
found in literature instances of thermal degradation
analysis based on continuously observation of heat-
ed fibre. The microscopic analysis of thermal degra-
dation process provides another kind of information
than above mentioned techniques (e.g. TD-FTIR).
The direct observation of heated fibres allows to
investigate even slight alteration of fibre’s particular
parts – shape of longitudinal view, existence of shrink-
age, fibre colour. This kind of information could be
important for finishing treatment process or setting of
appropriate cleaning parameters for the end users
(washing, drying or ironing temperature). Moreover,
optical microscopy with additional devices to control
of degradation temperature is economical, less time
consuming (easy way of preparing samples) in com-
parison to other advanced techniques.
The aim of this work is to present the analysis and
evaluation of the process of fibre thermal decomposi-
tion that is based on the microscopic, continuously
observation method. The final result of thermal decom-
position, according to standards is only the value of
ignition temperature [1, 17]. In the presented paper,
the analysis of the whole process of thermal decom-
position of fibres in a function of temperature togeth-
er with establishing their final temperature of thermal
decomposition was investigated. The typical stan-
dard test of ignition temperature has been enlarged;
the analysis of detail changes during thermal decom-
position process was investigated. Additionally, phe-
nomena accompanying fibre decomposition were
evaluated, such as longitudinal or transverse direc-
tions shrinkage. Applying the technique of identifica-
tion (microscopic method and attempt to burn) is
based on methodology included in the standards [1,
17]. Identification of materials using the microscopic
method together with the thermal analysis were per-
formed in the context of influence of fibre origin, i.e.
establishing whether fibres maintain their character-
istic features in a ready-made product.
EXPERIMENTAL WORK
Materials and Method
The material selected for tests comprised of a group
of natural plant fibres and synthetic fibres on the
basis of regenerated cellulose. Fibres that were eval-
uated were of the following origin: roving, knitting
yarn, weaving yarn, final products (fabrics, knitwear).
The different sources of tested fibres had implement-
ed due to simulation of real laboratory testing condi-
tions (identification of raw material composition using
optical microscopy). Due to the fact that all the anal-
ysed fibres are non- thermoplastic, most frequently it
is usually only the temperature of their decomposition
and the temperature of disintegration that is deter-
mined. In table 1 there are the types of fibres togeth-
er with their characteristic. All yarns taking under con-
sideration in this paper and being a source for tested
fibres were not finished (died or blenched). The pro-
posal of end usage of yarn (knitted or woven fabrics)
was connected with yarn structure and characteristic
(twist).
Since all of the tested materials belong to the group
of non-thermoplastic fibres, their physical state did
not change during rising the temperature of fibres,
but the chemical structure was altered as a result of
chemical decomposition of the polymer that created
the fibre [3]. Observations of the thermal degradation
process of the fibres were performed in the condi-
tions of heating using Dialux microscope equipped
with a heated table (maximum table heat temperature
was 350°C). The changes taking place during the
process of heating were noted together with the val-
ues of temperature at which they took place. The aim
of the test was not only to establish the temperature
of fibre decomposition, but also to characterise the
stages of thermal degradation that could be observed
in the change of colour or shrinkage. During the anal-
ysis, the behaviour of the fibre in the time of the con-
trolled burn process was described, including the fol-
lowing:
– change of fibre colour in time resulting from its pro-
gressive chemical destruction,
– fibre shrinkage and its intensity, and directivity
(change of the transverse dimension of the fibre or
a shrinkage along the fibre length),
– fibre deformation understood as a change in a
fibre shape and not classified as a shrinkage in
any direction.
In order to unify the results during their further pre-
sentation and analysis, the new qualitative scales
were assumed that included natural numbers. The
scales of changes in colour and longitudinal view
have been investigated during research process and
presented form is a result of evaluation of alternation
in different fibre structure and properties. Table 2
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2016, vol. 67, nr. 5
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includes descriptions referring to individual degrees,
however, there is a separate scale for colour change
and intensity of a shrinkage of fibres during heating.
On the basis of the new assumed qualitative scale
describing the process of thermal degradation of
fibres, the obtained results are presented in form of
figures.
THERMAL ANALYSIS OF FIBRES
As part of the preformed analysis, for each fibre a
characteristic of its thermal properties was prepared,
including temperature values of thermal decomposi-
tion. These values are accessible for some fibres in
literature, e.g. [2, 15]. Detailed results obtained for
fibres are presented in form of figures:
– change of fibre color in its temperature growth
function;
– intensity of fibre shrinkage during the temperature
increase.
Colour change of fibre’s structure
Figures 1–4 present a characteristic of colour change
(caused by thermal decomposition) that takes place
in fibres during the process of the temperature
increase. Figure 1 presents a summary of results for
fibres not presented in other figures. Figures 2–4
show detailed thermal characteristics for cotton, vis-
cose and flax fibres.
Having analyzed the graphs presented above with
thermal decomposition of fibres, the following can be
concluded:
– silk fiber decomposition (fig. 1) proceeded in a dif-
ferent manner due to the presence of sericin coat-
ing of the fibre. Initially, the destruction of the fibre
took place from inside of its structure and black
colour was a dominant one. Then, decomposition
included also the inside of the fibre where the
brown colour prevailed and finally, the fibre was
carbonized at the temperature of 290°C;
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2016, vol. 67, nr. 5
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Fig. 1. Thermal resistance of fibres
Fig. 2. Thermal resistance of cotton
RAW MATERIALS AND GENRES OF FIBRE
No. Raw material Sample
no. Fibre Fibre source
1cellulose
(cotton)
1a cotton 20 tex yarn dedicated for knitted fabrics
1b cotton roving
2 cellulose (hemp) 2a hemp 25 tex yarn dedicated for knitted fabrics
3 cellulose (jute) 3a jute loose fibre
4 cellulose (ramie) 4a ramie loose fibre
5cellulose
(flax)
5a flax 30 tex yarn from oakum, dry spinning, dedicated for weaving fabrics
5b flax 30 tex yarn, wet spinning dedicated for weaving fabrics
5c flax yarn took from final product
6regenerated
cellulose
6a viscose 20 tex yarn dedicated for knitted fabrics
6b viscose FR 20 tex yarn dedicated for knitted fabrics
7 bamboo cellulose 7 bamboo 20 tex yarn dedicated for knitted fabrics
8 soya protein 8 soya 25 tex yarn dedicated for knitted fabrics
9silk skleroproteine
(fibroine, sericin) 9 silk loose fibre
Table 1
THE SCALE OF THERMAL PROPERTIES
ASSESSMENT
Scale
degree Colour of fibre Shrinkage intensity
0 no changes no shrinkage
1 light brown light longitudinal shrinkage
2 middle brown severe longitudinal shrinkage
3 dark brown slight transverse shrinkage
4 light black severe transverse shrinkage
5 middle black deformation - curl
6 dark black
7 carbonized fibre
Table 2

– the highest thermal resistance was observed for
the flax fibre – about 330°C, whereas the lowest
for viscose fiber – 270°C;
– among the flax fibres, the highest thermal resis-
tance was observed for fibres in the final product,
however, this may be connected with the presence
of finishing (during the process of heating, there
were bubbles of liquid around the fibres). The level
of temperature value of the thermal decomposition
of the fibre is similar for fibres from all analyzed
sources (differences are around 10°C);
– viscose fibres present a similar thermal resistance
and slight differences in the characteristic picturing
their decomposition do not point to any distinct
properties in this area. With reference to viscose
fibres, modifications are possible (e.g. as a result
of incorporating a substance into the fibre) that
allow to obtain various thermal properties – e.g.
fibres with higher thermal resistance.
Thermal shrinkage evaluation
Figures 5–7 present the intensity of shrinkage pro-
cess of the fibres under higher temperature condi-
tions. Figure 5 presents all types of fibres that were
analysed and for which there was a shrinkage during
the process of heating. Figure 6 and 7 concern the
fibres of flax and viscose.
While analysing the figures presenting the process of
thermal shrinkage of fibres during heating, the follow-
ing can be observed:
– for cotton and silk fibres, the phenomenon of
shrinkage during the process of thermal destruc-
tion did not occur;
– the strongest shrinkage, both longitudinal to the
axis of the fibre (shrinkage on the axis) and in the
direction perpendicular to the axis of the fibre
(reducing the dimension of the fibre) appeared for
the fibres of viscose and soya;
– above the temperature of 260°C in all evaluated
fibres, a shrinkage is visible, however, for viscose
fibres it is continuous whereas for all the others the
shrinkage is of temporary character (it appears at
certain temperatures to disappear later and re-
appears at higher temperature values);
– for soya fibres, deformation appears that is indi-
rectly connected with the phenomenon of shrink-
age in both directions mentioned above. Changing
the shape of the fibre is its distinct property (a fibre
becomes crimped and twisted which suggests
uneven shrinkage of its individual fragments);
– in the group of flax fibres, the highest thermal
resistance (with reference to shrinkage) are pre-
sented by fibres taken from a final product, which
was noted during the analysis of the change in the
fibre colour, for other fibres shrinkage process
begins rather rapidly, at about 280–290°C and
lasts until fibre carbonization.
– in case of viscose fibres, fibres taken from yarn
(6a) present lower thermal resistance, shrinkage
appears at the very beginning of the process of
fibre heating and is rapid (presence of a shrinkage
in both directions against the axis of the fibre). For
FR viscose, shrinkage appears later and is limited
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2016, vol. 67, nr. 5
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Fig. 3. Thermal resistance of viscose
Fig. 4. Thermal resistance of flax
Fig. 5. Thermal resistance of fibres – shrinkage
Fig. 6. Thermal resistance – flax fibre shrinkage
Fig. 7. Thermal resistance – viscose fibre shrinkage

to a longitudinal direction against the axis of the
fibre. The shrinkage becomes stronger at about
240–250°C and lasts until fibre carbonization.
RESULTS
Summarising the presented results of research into
identification of the selected natural and man-made
fibres using a microscopic method on the basis of a
tested sample the following may be concluded:
●the source of cotton, flax and viscose fibre (in rela-
tion to the degree of a textile material treatment)
may become the reason of their various thermal
properties both in terms of temperature of thermal
decomposition and its characteristics;
●the lowest thermal resistance among the evaluat-
ed fibres have viscose fibres and they are charac-
terised by shrinkages occurring at much lower
temperatures than for the other fibres that were
evaluated;
●the highest thermal resistance is presented by flax
fibres collected from the final product, which was
also confirmed by the analysis of their colour change;
●soya fibre was the most distinct one as it was
characterised by a strong deformation (curl) directly
after the increase of temperature (around 45°C).
The aim of this work was to establish whether fibres
maintain their characteristic features in terms of their
thermal properties in a final product (knitting yarn,
fabric knitwear) as fibres evaluated in a laboratory
most frequently are obtained from products. Basing
of the performed tests, it was stated that for cotton
and flax fibres, the source of raw material may be
important during the process of identification with ref-
erence to thermal decomposition. As for viscose
fibres (or when there is likelihood of their occur-
rence), it was found that these fibres are charac-
terised by varied thermal shrinkage, depending on
their type. On the basis of the presented results, it
may be concluded that fibres of the same raw mate-
rial composition may present different properties in
terms of thermal shrinkage and pace of decomposi-
tion at certain temperature, which should be consid-
ered during the treatment process and maintenance
using higher or high temperature.
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2016, vol. 67, nr. 5
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[8] H. Zhang, L. Hang, Structural changes of hemp fibres modified with chitosan and BTCA. In: Industria Textila 2010,
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[9] Santos O., Passos R, et al., Processing and thermal properties of composites based on recycled PET, sisal fibers,
and renewable plasticizers, In: Journal of Applied Polymer Science vol. 131, no. 12, 2014 p. n/a.
[10] Sudhakara, P., et al., Thermal, mechanical, and morphological properties of maleated polypropylene compatibilized
Borassus fruit fiber/polypropylene composite, In: Journal of Applied Polymer Science 2013, vol. 128, no. 2 pp. 976–982
[11] Gutierrez, M. Ch., Marco-Aurelio de P., Felisberti M. I., Cellulose acetate and short curauá fibers biocomposites
prepared by large scale processing: Reinforcing and thermal insulating properties, In: Industrial Crops & Products
2014, vol. 52, pp. 363–372
[12] Fei, P., et al., Thermal properties and crystallization behavior of bamboo fiber/high-density polyethylene
composites: Nano-TiO2 effects, In: Journal of Applied Polymer Science 2014, vol. 131, no. 3, pp. n/a.
[13] Vineis, Claudia, Annalisa Aluigi, Claudio Tonin, Outstanding traits and thermal behavior for the identification of
speciality animal fibres, In: Textile Research Journal 2011, vol. 81, no. 3, pp. 264–272
[14] Hu, Liu-Hua, Shao-Lin Xue, Ling Li., Research on qualitative & quantitative identification methods of Shengma
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[15] Wu, Pei-Yun Wool, Qualitative identification of Shengma fiber, In: Textile Journal 2010, vol. 38, no. 4, pp. 44–47
[16] “The guide of textile” Part 1, published by House of Textile and Food Industry, Warsaw 1961, chapter 10 – Plant
textile raw materials, chapter 11 – Animal textile raw materials.
[17] PN-72/P-04604 “Methods of testing textiles – Fibre identification”
Authors:
IZABELA JASIŃSKA
Textile Research Institute
92-103, 5/15 Str. Brzezińska
Lodz-POLAND
e-mail: ijasinska@iw.lodz.pl

INTRODUCTION
The basic staple spun yarn manufacturing in ring
spinning system consists of the main production pro-
cesses namely; opening, cleaning, blending, carding,
drawing, roving, ring spinning, winding and packag-
ing [1]. The raw material of the yarn is introduced to
the blowroom as fiber bales and they are converted
into yarn form by following the production steps
sequentially. Each yarn production is performed by
using distinctive raw material. So, unique code is
used for each yarn production even they have the
same fiber type such as cotton, viscose etc. In fully
automated mills, the material transfer between the
production steps are performed by using automation
systems. Finally, the yarn bobbins are packaged by
using a robotic system.
When the different raw materials are accidentally
mixed in any step of the yarn production, it causes
fiber mixture fault on the yarn bobbin. Despite the
new automation systems used in yarn manufacturing
mills, the fiber mixture fault is still inspected by
human eye. The yarn packages are loaded on a creel
and they are detected in a UV lightened room. This
process is time consuming and it has the risk of yarn
fault missing. For fully automated mills, this inspec-
tion method causes more problems, since the human
intervention is not permitted during manufacturing.
The fiber mixture bobbins cause more problems after
weaving operation. Since each fiber has different dye
affinity characteristics, this fault causes high cost due
to off-quality fabric production.
In the literature, there are some studies on foreign
material and fiber detection [2–7]. In these studies,
machine vision systems have been designed for fiber
lint inspection. The studies are especially performed
for cotton lint. Any study or commercially developed
system that achieves the fiber mixture fault inspec-
tion on yarn bobbin has not been encountered.
In this study, a prototype vision inspection system
was developed to inspect the yarn bobbins for fiber
mixture fault and image processing algorithm was
prepared. Yarn samples with fiber mixture fault and
no fault were used. The samples are inspected by
using the prototype vision inspection system to deter-
mine the mixture fault existence.
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Development of a machine vision system for yarn bobbin inspection
H. İBRAHIM ÇELİK
REZUMAT – ABSTRACT
Dezvoltarea unui sistem de control vizual pentru inspecţia bobinelor de fire
Când diferite materii prime sunt amestecate în orice etapă a producției de fire, se creează defecte de fibre pe bobina
de fire. Deoarece fiecare fibră are caracteristici diferite de afinitate a colorantului, acest element poate determina
producerea unei ţesături de calitate mai slabă. În ciuda noilor sisteme de automatizare utilizate în fabricile de producţie
a firelor, defectele amestecurilor de fibre sunt încă inspectate de către ochiul uman. Acest proces este mare consumator
de timp, iar evaluarea se face în mod subiectiv. Mai mult decât atât, multe bobine cu defecte de amestec al fibrelor pot
fi trecute cu vederea de către operator. În acest studiu, a fost dezvoltat un prototip de sistem de control vizual pentru a
detecta defectele amestecului de fibre prin utilizarea metodei de procesare a imaginii. S-a urmărit ca defectele
amestecului de fibre al bobinelor de fire să poată fi detectate automat, iar evaluarea defectului să poată fi făcută în mod
obiectiv. Algoritmul de detectare a defectelor s-a bazat pe filtrul Wiener, filtrul Gaussian și pe operațiile morfologice. Șase
bobine de fire: trei cu defecte ale amestecului de fibre și alte trei fără defecte ale amestecului, în calitate de grup de
control, au fost verificate cu succes, iar zonele cu defecte au fost etichetate.
Cuvinte-cheie: control vizual, amestec de fibre, inspecţia bobinelor de fire, procesarea imaginii, identificarea defectelor
Development of a machine vision system for yarn bobbin inspection
When the different raw materials are blended in any step of the yarn production, it causes fiber mixture fault on the yarn
bobbin. Since each fiber has different dye affinity characteristics, this fault causes off-quality fabric production. Despite
the new automation systems used in yarn manufacturing mills, the fiber mixture fault is still inspected by human eye.
This process takes long time and the evaluation is made subjectively. Furthermore, many bobbins with fiber mixture fault
may be escaped from the worker notice. In this study, a prototype of vision inspection system was developed to detect
the yarn fiber mixture fault by using image processing method. It was aimed that the fiber mixture faults of the yarn
bobbins can be detected automatically and the fault evaluation can be made objectively. The fault detection algorithm
was based on Wiener filtering, Gaussian filtering and morphological operations. Six yarn bobbins; three of them with
fiber mixture fault and other three having no mixture fault as control group were detected successfully and the fault areas
were labeled.
Key-words: Machine vision, fiber mixture, yarn bobbin inspection, image processing, fault detection

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EXPERIMENTAL PART
Material
Six 100 % cotton yarn samples were used. Three of
them comprise mixture fault caused by several rea-
sons i.e. cotton fiber comes from different bales,
winding of different types of yarn cops on the same
bobbin etc. Other three samples did not have any
fiber mixture, they are evaluated as control group.
The yarn bobbins were supplied from different yarn
spinning mills, they were selected randomly.
Vision inspection system for yarn package
inspection
Prototype vision inspection system has been devel-
oped in order to acquire image of the yarn bobbin
properly and to analyze it for the fiber mixture exis-
tence. The system consists of lightening unit, High
Density (HD) web camera, cabin and computer (fig-
ure 1). The most important parameter that deter-
mines the reflectance of the yarn is the fiber type
comprising the yarn structure. Each fiber type has dif-
ferent reflectance values under the same lightening
condition. So, Ultra Violet (UV) fluorescents are used
as lightening unit to identify different fiber groups
according to their different luminance values [8]. The
image acquisition process is achieved by using a
Logitech HD Pro Webcam C920. The resolution of
the camera 1920×108 pixels. The camera is con-
nected to the computer via USB port. Since any light
entrance expects the UV lightening source will
change the image analyzing result, the cabin is
designed to provide a darkroom condition.
Method
The algorithm developed for detection of fiber mix-
ture in a yarn package consists of noise removing fil-
ter, Gaussian filter and morphological operation (fig-
ure 2). Gaussian filter is used to segment the regions
that have different intensity values according to the
neighborhood relation. The morphological operations
are used to remove the noises and to make the
regions clearer.
The image frame may have noises because of illumi-
nation condition. It is recommended that the noise
should be removed to get the true pixel intensity val-
ues. So, the image frame captured from the HD cam-
era is applied Wiener low-pass filter for noise remov-
ing. Wiener estimates the local mean and the
variance around each pixel. Wiener filter makes its
estimation by using following equation [9]:
σ2– ν2
b(n1,n2)= μ+ (a(n1,n2)– μ) (1)
σ2
where ν2is the noise variance, μand σ2are the local
mean and local variance around each pixel respec-
tively.
The noise filtered image is then applied Gaussian fil-
tering. The Gaussian filter is used for image smooth-
ing as low-pass filter. The image frame is convolved
with Gaussian function [9]:
–(n1
2+n2
2)
h(n1,n2)= e2σ2(2)
where, n1and n2are the locations of the related pixel,
σ2 is the variance of the neighborhood. The filtered
image is converted into binary form. The binarization
operation is carried out by using a threshold level as
following:
0 a(i,j) < T
P(i,j)=
{
(3)
1 a(i,j) > T
All pixel values a(i,j) greater than the threshold value
(T) in the input image is replaced with the value 1
(white) and all other pixels values are replaced with 0
(black). The threshold value (T) is determined by trial
and error method. Thus, the pixels that have close
gray level values are separated and detected.
The binary image is applied closing morphological
operation. Closing is the name given to the morpho-
logical operation of dilation followed by erosion with
the same structuring element
A⋅ B= (A ⊕ B) ⊖ B (4)
Fig. 1. Prototype yarn package vision inspection system
Fig. 2. Flow chart of the algorithm

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Fig. 3. Fiber mixture inspection of yarn bobbins
(i) yarn bobbin sample
(a) RGB (b) Gaussian filtered (c) Binary (d) Labeled
(ii) yarn bobbin sample
(a) RGB (b) Gaussian filtered (c) Binary (d) Labeled
(iii) yarn bobbin sample
(a) RGB (b) Gaussian filtered (c) Binary (d) Labeled
Fig. 4. Inspection of faultless yarn bobbins
(iv) yarn bobbin sample
(a) RGB (b) Gaussian filtered (c) Binary (d) Labeled
(v) yarn bobbin sample
(a) RGB (b) Gaussian filtered (c) Binary (d) Labeled
(vi) yarn bobbin sample
(a) RGB (b) Gaussian filtered (c) Binary (d) Labeled

Closing operation is used to eliminate
specific image details smaller than
the structuring element. This morpho-
logic operation connects objects that
are close to each other and fills up
small holes. Thus the boundary of the
object is made smoother [10]. Finally,
the boundaries of the detected
regions are labeled.
RESULTS AND DISCUSSION
The fiber mixture existence of the six
yarn bobbins are detected by using
prototype vision inspection system.
After the yarn bobbin image frames
are acquired via the developed sys-
tem, the image frames are analyzed
by applying the developed algorithm.
Thus, the boundaries of three bob-
bins that have fiber mixture faults are
detected and labeled successfully
(figure 3). Other three yarn bobbins
that consist of single fiber type are
detected as control group (figure 4).
The yarn samples with fiber mixture
faults have different amount of mix-
tures at different places of the bob-
bins.
A user interface is prepared on
MATLAB® program to apply the
algorithm easily (figure 5). The user
interface consists of Exit, Image
Acquisition, Fiber Mixture Inspection
and Fault Labeling buttons. After the
yarn bobbin is placed into the cabin,
the camera is activated and the
image frame is acquired from the top
of the yarn bobbin by using Image
Acquisition button (figure 5). By using
Fiber Mixture Inspection button, the
image frame is analyzed by applying
the developed algorithm (figure 2)
and the result is displayed on the
screen (figure 6). The detected
regions are labeled by using Fault
Labeling button (figure 7).
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Fig. 5. User interface and image acquisition application
Fig. 6. Fiber mixture inspection algorithm application
Fig. 7. Fault labeling application
CONCLUSION
In this study a prototype vision inspection system
was developed for detection of yarn bobbin fiber
mixture fault. Under the same lighting condition the
fibers have different luminance values. This property
provides the distinction of the fiber mixtures. The
image processing algorithm developed for detection
of the regions having different gray level values was
based on Wiener filter, Gaussian filter, binarizaiton
and morphological operation. The fiber mixture faults
with different amount and locations were detected
successfully and the boundaries are labeled by
applying the developed algorithm. The fault detection
algorithm was applied via a user interface prepared
by using MATLAB®.
The study was performed as a prototype system
design. The system will be improved and adapted to
yarn manufacturing mill. It was aimed that the yarn
bobbin inspection can be achieved in shorter time,
objectively and accurately. By using this machine vision

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BIBLIOGRAPHY
[1] Lawrence, C.A., Fundamentals of spun yarn technology, In: CRC Press LLC, Boca Raton London New York
Washington, D.C., 2003, pp. 34–35.
[2] Yang, W., Li D., Zhu L., Kang Y., Li, F., A new approach for image processing in foreign fiber detection. In:
Computers and Electronics in Agriculture, 2009, vol. 68, issue 1, pp. 68–77.
[3] Li, D., Yang, W., Wang, S., Classification of foreign fibers in cotton lint using machine vision and multi-class support
vector machine. In: Computers and Electronics in Agriculture, 2010, vol. 74, issue 2, pp. 274–279.
[4] Su, Z., Tian Y. G., Gao, C., A machine vision system for on-line removal of contaminants in wool. In: Mechatronics,
vol. 16, issue 5, pp. 243–247.
[5] Yuhong, D., Yongheng, L., Xiuming, J., Wenchao, C., Donghan, G., Research of foreign fibers in cotton yarn defect
model based on regression analysis. In: The Journal of The Textile Institute, 2015, DOI: 10.1080/00405000.
2015.1084150.
[6] Xinhua, W., Shu, W., Laiqi, X., Baoguo, S., Meijin, L., Identification of foreign fibers of seed cotton using hyper-
spectral images based on minimum noise fraction. In: Transactions of the Chinese Society of Agricultural
Engineering, 2014, vol. 30, issue 9, pp. 243–248.
[7] Pai, A., Sari-Sarraf, H., Hequet, E. F., Recognition of cotton contaminants via x-ray microtomographic image
analysis. In: IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2004, vol. 40, issue 1, pp.77–85.
[8] Akgün, M., Alpay, H. R., Becerir, B., Kumaş yapısal parametreleri ile reflektans değerleri arasındaki ilişkilerin
değerlendirilmesi. In: Uludağ University Journal of The Faculty of Engineering and Architecture, 2012, vol.17,
issue.1, pp. 93–106.
[9] Natick, M.A., Image Processing Toolbox™ 7 User’s Guide. In: The MathWorks, Inc.
[10] Sonka, M., Hlavac, V., Boyle, R., Image processing, analysis and machine vision. International student edition.
In: Thomson Corporation, USA, 2008, pp. 665–666.
Authors:
HALIL IBRAHIM CELIK
Gaziantep University
Faculty of Engineering, Department of Textile Engineering
Sehitkamil-27310
Gaziantep - TURKEY
e-mail: hcelik@gantep.edu.tr
Corresponding author:
HALIL IBRAHIM CELIK
hcelik@gantep.edu.tr
system, the employment cost would be reduced and
the costs related with off-quality would be decreased.
Acknowledgements
The yarn bobbin samples used in this study are supplied by
Kipaş Holding A.Ş and Selçuk Iplik Sanayi ve Ticaret A.Ş.
Author is grateful for the help of the companies in support-
ing this study. This study is supported by the Gaziantep
University Scientific Research Projects Management Unit
in the content of MF. 14.21 project. Author also thank to Akif
Harun BATUR for his assistance in prototype system con-
struction.

INTRODUCTION
In recent years, the usage of electrical and electron-
ic devices increases rapidly. Electronic devices gen-
erate intentionally or unintentionally electromagnetic
(EM) energy. EM fields have both electric and mag-
netic field components, and they have hazardous
effects on the living tissues and electronic systems
[1–11]. Unwanted reception of EM waves may create
an interference phenomenon that has adverse effect
called electromagnetic interference (EMI) problem,
on the performance of electrical/electronic equipment
[12]. The hazardous effect of EM waves on human
health can also be considered as an EMI problem
since the human body is actually an electrical system
with a huge nervous system [4]. Because of the
detected negative effects of electromagnetic waves,
it has become a necessity to find the protection ways
from electromagnetic radiation.
EM shielding is a process by which a material is
able to reduce the transmission of electromagnetic
radiation that affects the humans/equipment [13].
Traditionally, metals are used for electromagnetic
shielding; however, these materials are heavy,
expensive, inflexible and may be subject to thermal
expansion and metal oxidation, or corrosion prob-
lems associated with their use [14]. Owing to these
disadvantages of classical materials used for shield-
ing, more flexible, lighter and low cost electrically
conductive textile products have become increasing-
ly more preferable.
There are various studies about fabric structures
having electromagnetic shielding effectiveness (SE)
in literature. Cheng investigated the SE of plain, 1×1
rib and 1×2 rib knitted fabrics which were produced
with stainless steel (SS)/PES blended yarns,
SS/Stainless Steel Wire (SW)/PES, and SW/PES
core-spun yarns in different blend ratios. The SE
tests of fabrics were performed at 30 kHz–3000 MHz
frequency range by using coaxial transmission line
method. It was found that as the steel ratio of the
yarn increases, the SE of the fabrics increases. It
was interpreted that the SE of the 1×2 rib knitted
structures are higher than that of the other knitted
fabric structures due to the closer structure compared
to the other fabrics [14].
Ciesielska and Grabwska investigated the SE of knit-
ted fabrics with three types of knit structures, namely
left-right stitch, double-layer, and double-layer with
additional fillings, which contained ferromagnetic
materials and electro conductive materials. They
interpreted that the SE of knit structures depends on
the arrangement of ferromagnetic and electro con-
ductive materials in the knit structure [15].
Lin et. al. investigated the SE of double jersey fabrics
knitted with hybrid core spun yarns. The core spun
yarns were produced with SS wire and Cu wire as
core materials and, rayon yarn and polyester/rayon
(65/35) yarn as cover materials. The SE of double
jersey fabrics were tested with a coaxial transmission
line holder in the frequency range of 30 MHz to
3 GHz. It was reported that double jersey fabrics
have the highest SE value in the 30–100 MHz fre-
quency range and they have about 8–15 dB SE in
this frequency range [16].
Electromagnetic shielding effectiveness of spacer knitted hybrid fabrics
HUSEYIN GAZI TURKSOY SINEM BILGIN
REZUMAT – ABSTRACT
Eficacitatea ecranării electromagnetice a tricoturilor spațiale hibride
În acest studiu, au fost realizate tricoturi spațiale având eficacitate de ecranare electromagnetică prin utilizarea diferitelor
tipuri de fire conductive electric. Eficacitatea ecranării țesăturilor dezvoltate a fost testată prin standardul ASTM 4935-
10. Încercările au fost efectuate la intervale de frecvență de 100–1000 MHz. Analiza varianței și a metodelor de
Comparații multiple au fost folosite pentru evaluarea rezultatelor testelor. Rezultatele testelor indică faptul că tipurile de
fire conductoare și dispunerea acestor fire în structurile ţesăturilor afectează în mod semnificativ eficacitatea ecranării
tricoturilor spațiale hibride.
Cuvinte-cheie: eficacitatea ecranării (SE), fir metalic, fir cu miez, țesătură spațială
Electromagnetic shielding effectiveness of spacer knitted hybrid fabrics
In this study, spacer knitted fabrics having electromagnetic shielding effectiveness have been developed by using
various types of electrically conductive yarns. Shielding effectiveness of developed fabrics has been tested by standard
ASTM 4935-10. The tests have been carried out at 100–1000 MHz frequency ranges. Analysis of variance and Multiple
Comparisons methods have been used for evaluating the test outcomes. The test results indicate that the conductive
yarn types and arrangement of these yarns in fabrics’ structures significantly affect the shielding effectiveness of spacer
knitted fabrics.
Keywords: Shielding effectiveness (SE), metal wire, core yarn, spacer fabric
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Soyaslan et al. examined the SE of seven knitted
fabrics by using ASTM D 4935-10 Coaxial holder
method. The knitted fabrics in plain knitting, weft in-
laid plain knitting, 1×1 rib and weft in-laid 1×1 rib knit-
ting structures were produced with copper wire and
cotton blended yarns. The SE of these fabrics was
made at 27 MHz – 3 GHz frequency range. Test
results showed that the weft-knitted structures have
10–40 dB shielding effectiveness under the frequen-
cy of 500 MHz [17].
As mentioned above, conventional knit structures
have been preferred in many studies which are about
developing fabrics offering electromagnetic shielding.
However, conventional knit structures have a handi-
cap for electromagnetic shielding property when they
compared to woven fabrics. Differently from woven
fabrics, the textile yarns can be found only in produc-
tion direction or only vertically to it for knitted fabrics.
Therefore, the conducting yarns can only be incorpo-
rated into one direction and consequently a shielding
is achieved for electrical field components in just that
direction for knit structures.
In the last few years, spacer knitted fabrics have
been reached a greater level of importance for tech-
nical applications.Spacer fabrics have three dimen-
sional structures consisting of two outer surfaces and
a connection layer which combines two outer sur-
faces. In this study, due to their special construction,
the SE properties of spacer knitted fabrics containing
various types of electrically conductive yarns were
investigated at the frequency ranges of 100–300 MHz
and 300–1000 MHz.
MATERIALS AND METHODS
In the scope of study, 13 spacer fabrics having the
same knitting structure were fabricated from different
raw materials in front face, connection, back face, fill-
ing parts. Mayer & Cie, OVJA 1.6 E double-plate cir-
cular knitting machine was used to knit spacer fabric
samples. The yarn types and their arrangements in
the fabric structures are summarized in table 1. The
microscopic images of conductive yarns used in this
study are given in figure 1. In addition knitted needle
diagram belonging to front face, connection, back
face and filling yarns are given in figure 2.
SE measurements of fabric samples were made with
coaxial holder method based on ASTM D 4935 stan-
dard for 100–1000 MHz frequency ranges [18]. This
standard determined the shielding effectiveness of
the fabric samples by using the transmission line
method. The measurement device consists of a net-
work analyzer (R & S ZVB20) generating and receiv-
ing the electromagnetic signals and a coaxial trans-
mission line test fixture [19]. The shielding effec-
tiveness is determined by comparing the difference in
attenuation of a reference sample to the test sample,
taking into account the transmission lines with this
device. The reference and the test measurement
were performed on the same material in this study
(figure 3).
The shielding effectiveness was determined from
equation (1):
E1
SE = 20 log (1)
E2
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YARN TYPES AND ARRANGEMENT IN THE FABRIC STRUCTURES
Fabric Code Front Face Connection Back Face Filling
1Ne 24/1 hybrid1Ne 24/1 cotton Ne 24/1 cotton 300 denier PES
2 Ne 24/1 cotton Ne 24/1 cotton Ne 24/1 hybrid 300 denier PES
3 Ne 24/1 hybrid Ne 24/1 cotton Ne 24/1 hybrid 300 denier PES
4 Ne 24/1 cotton Ne 24/1 hybrid Ne 24/1 cotton 300 denier PES
5 Ne 24/1 cotton Ne 24/1 cotton Ne 24/1 cotton Ne 24/1 hybrid
6 Ne 24/1 hybrid Ne 24/1 hybrid Ne 24/1 hybrid Ne 18/2 hybrid2
7 Ne 24/1 hybrid Ne 24/1 hybrid Ne 24/1 hybrid Ne 20/2 hybrid-a3
8 Ne 24/1 hybrid Ne 24/1 hybrid Ne 24/1 hybrid Ne 20/2 hybrid-b4
9 Ne 24/1 hybrid Ne 24/1 hybrid Ne 24/1 hybrid Ne 30/1 carbon/ cotton5
10 Ne 24/1 hybrid Ne 24/1 hybrid Ne 24/1 hybrid Ne 30/1 silcot6
11 Ne 24/1 cotton Ne 24/1 cotton Ne 30/1 silcot 300 denier PES
12 Ne 30/1 silcot Ne 24/1 cotton Ne 24/1 cotton 300 denier PES
13 Ne 30/1 carbon/ cotton Ne 24/1 cotton Ne 24/1 cotton 300 denier PES
Table 1
1 Ne 24/1 hybrid: core spun yarn containing 20 µ SS
2 Ne 18/2 hybrid: twisted two 18/1 (core spun yarn containing 20 µ SS) yarn
3Ne 20/2 hybrid-a: twisted two Ne 20/1 cotton yarn and 20 µ SS
4Ne 20/2 hybrid-b: twisted two Ne 20/1 cotton yarn and 35 µ SS
5Ne 30/1 carbon/cotton – 10/90
6Ne 30/1 silcot: silver covered polyamide/cotton – 10/90

E1is the value of the electrical component
and is measured with the reference sam-
ple. E2is measured with the test sample.
In daily life, electromagnetic fields which we
have been exposed are at the VHF
(30–300 MHz) and UHF (300–3000 MHz)
frequency ranges. The devices frequently
used such as radio, television, mobile
phones, cordless phone emit electromag-
netic radiation in these two frequency
ranges. For this reason, after measuring
SE values for 100 different frequencies
between 100 and 1000 MHz at 3 different
locations for each fabric type, means of the
SE values of these selected locations of the
samples were calculated separately for the
frequency intervals 100–300 MHz as low
frequency interval and 300–1000 MHz as
high frequency interval. In order to evaluate
the shielding performances of each fabric
type, these mean values were compared
and statistically evaluated for mentioned
frequency intervals.
RESULTS AND DISCUSSIONS
The mean SE values of spacer fabric sam-
ples for 100–300 MHz and 300–1000 MHz
frequency intervals are given graphically in
figure 4 and figure 5 respectively. According
to ANOVA results, the fabric type has sta-
tistically significant effect on SE values at
both 100–300 MHz and 300–1000 MHz fre-
quency intervals (p=0.000).
When SE values at 100–300 MHz frequency
range of 1, 12 and 13 coded fabrics having
same yarns as connection, back face and
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Fig. 1. Microscopic images of conductive yarns used in this study
Fig. 2. The knitted report and interface section of fabric
samples
Fig. 3. Test set up of coaxial transmission line method
Ne 30/1
carbon/cotton
10/90
Ne 30/1 silcot:
silver covered
polyamide/cotton
10/90
Ne 24/1 hybrid:
core spun yarn
containing
20 µ SS
Ne 20/2 hybrid-a:
twisted two
Ne 20/1 cotton
yarn and 20 µ SS
Ne 20/2 hybrid-b:
twisted two
Ne 20/1 cotton
yarn and 35 µ SS
Ne 18/2 hybrid:
twisted two 18/1
core spun yarnS
filling yarns are compared, it is seen that SE values
of 12 coded fabric containing silcot in front face is
lower than that of 1 coded fabric with core yarn in
front face and 13 coded fabric with carbon/cotton yarn
in front face (figure 4). This result shows that usage
of silcot in front face doesn’t contribute to SE value of
fabric positively comparing to usage of core yarn and
carbon/cotton yarn in front face. Also, according to
Tukey test results, difference between means of SE
at 100–300 MHz frequency range of 1 and 13 coded
fabrics is not statistically significant (p=0.989).
When SE values at 100–300 MHz frequency range of
2 and 11 coded fabrics having same yarns as front
face, connection and filling but having different back
face yarns are compared, it is seen that 2 coded fab-
ric having core yarn containing metal as back face
yarn provides SE, 11 coded fabric having silcot yarn
on its back face does not have any SE (figure 4).
According to Tukey test results, difference between
means of SE at 100–300 MHz frequency range of
2 and 11 coded fabrics is statistically significant
(p=0.00).
When 1 and 3 coded fabrics are compared, 1 coded
fabric having cotton yarn in back face has lower SE
value than that of 3 coded fabric having core yarn in

back face (figure 4). It shows that usage of core yarn
containing metal wire in the fabric effects SE value
positively.
6, 7, 8, 9 and 10 coded fabrics have same front face,
connection and back face, but their filling yarns are
different. When these fabrics are compared by using
Tukey test, the differences between mean values of
SE at 100–300 MHz frequency interval of 9 and 10
coded fabrics are statistically significant (p=0.032),
but differences between mean values of SE belong-
ing to other fabrics in this group are not statistically
significant (p>0.05). 10 coded fabric containing silcot
yarn in filling has higher SE value at 100–300 MHz
frequency range than 9 coded fabric containing car-
bon/cotton yarn in filling (figure 4). Contrast to usage
of silcot in front face, when it is used as filling yarn, it
has positive effect on SE value comparing to usage
of carbon/cotton yarn as filling yarn.
According to Tukey test results, when SE values at
300–1000 MHz frequency range of 1, 12, and 13
coded fabrics which have respectively core yarn, sil-
cot and carbon as front face but have same yarns as
connection, back face and filling yarns are compared,
it is found that differences between mean values of
SE at 300–1000 MHz frequency range of these fab-
rics are statistically significant (p=0.00). 1 coded fab-
ric has the highest SE value. It is followed by 13 and
12 coded fabrics (figure 5).
When SE values at 300–1000 MHz frequency range
of 2 and 11 coded fabrics having same front face,
connection and filling yarns, but having different back
face yarns are compared, it is seen that 2 coded fab-
ric containing core yarn with wire in back face shows
SE (24.16 dB), but 11 coded fabric containing silcot
does not have SE (0.51 dB) ability as shown in fig-
ure 5.
According to Tukey test results, when SE values at
300–1000 MHz frequency range of 6, 7, 8, 9, and 10
coded fabrics having same front face, connection
and back face yarns, but having different filling yarns
are compared, 10 coded fabric having silcot in filling
yarn has statistically higher SE value than that of
other fabrics in this group except for 8 coded fabric
(p=0.00). Because difference between means of SE
values at 300–1000 MHz frequency of 8 and 10
coded fabrics is not statistically significant (p=0.513).
On the other hand, difference between means of SE
values at 300–1000 MHz frequency range of 6, 7,
and 8 coded fabrics is not statistically significant
(p>0.005).
CONCLUSIONS
In our daily life, electromagnetic fields which we often
have been exposed are at the VHF (30–300 MHz)
and UHF (300–3000 MHz) frequency ranges. In this
study, the SE properties of spacer knitted fabrics
containing various types of electrically conductive
yarns were investigated in the frequency ranges of
100–300 MHz and 300–1000 MHz. Research results
indicate that when silcot yarn is used in the fabric
without metal wire, it does not have electromagnetic
shielding. On the other hand, it is seen that when
core spun yarns containing metal wire are used in
front face, connection and back face, the fabric hav-
ing silcot yarn in the filling has higher SE value than
that of the fabrics having 18 (core)/2 yarn, twisted
(20/2 p– 20 µ SS) and carbon/cotton as filling yarns.
Analysis results justified that the conductive yarn
types and arrangement of these yarns in fabric struc-
ture have an important effect on electromagnetic
shielding effectiveness of spacer knitted fabrics.
ACKNOWLEDGMENTS
This work was supported by the Erciyes University
Scientific Research Projects Unit (BAP) with FBY-11-3736
coded project. The authors would like to thank the BAP for
its financial support.
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Fig. 4. The mean SE values of fabric samples
in the frequency interval of 100–300 MHz
Fig. 5. Comparison of SE mean values of fabric samples
in the frequency range of 300–1000 MHz
BIBLIOGRAPHY
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model of stainless steel composite fabric, In: The Journal of the Textile Institute, 2014
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Authors:
HUSEYIN GAZI TURKSOY1
SINEM BILGIN2
Erciyes University
1Faculty of Engineering, Department of Textile Engineering
2Faculty of Engineering, Department of Textile Engineering
Talas-38030
Kayseri-TURKEY
e-mail: hgazi@erciyes.edu.tr
Corresponding author:
HUSEYIN GAZI TURKSOY
hgazi@erciyes.edu.tr
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INTRODUCTION
There are many working places where the work is
performed in artificial cold environment: manual oper-
ations and storage of raw materials, processing of
food in cooling chambers of warehouses, air explo-
sive freezing of raw materials in the manufacture of
frozen products, etc. The study of has shown that
much more workers, than supposed, are occupied
in artificial cold environment: in food processing
industry, freezers, cold departments of supermarkets,
etc. [1]
The work in natural and artificial cold has very similar
features: in both cases the impact of cold could be
dangerous for the human body. Therefore, workers
must be provided with cold protective clothing.
However, there are also specific characteristics of the
occupation in artificial cold environment:
● The artificial cold environment is more stable in
temperature, air velocity and humidity fluctuations,
which helps the proper selection of protective
clothing. In natural cold environment the tempera-
ture changes during the 24-hour period, which
requires variation in the protective clothing’s
insulation.
● Continuous cold air flows in the artificial cold facil-
ities lead to appearance of body temperature
asymmetry (asymmetric cooling) and faster heat
loses due to forced convection.
● The workers in artificial cold environment move
more frequently between cold and warmer envi-
ronment, which provokes higher strain on the ther-
moregulation system of the body.
● Work in a sitting posture or static work is more fre-
quently observed in artificial cold, which is
particularly harmful for the body.
● The clothing for artificial cold environment may be
required to have additional protective features: i.e.
against chemical hazards, mechanical hazards,
etc., because of occupational safety regulations.
One of the approaches to assess the cold stress in
cold environment is to assess the wind-chill tempera-
ture [2]. The wind-chill temperature is much more
appropriate to be used in outdoor environment, how-
ever; though there are some exceptions, associated
with artificial cold environment (i.e. large tunnel freez-
ers with fast moving cold air). The Required Clothing
Insulation (IREQ) index is very suitable for the assess-
ment of the activities in artificial cold environment, as
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2016, vol. 67, nr. 5
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The effect of clothing insulation on the thermophysiological comfort
of workers in artificial cold environment
RADOSTINA A. ANGELOVA
REZUMAT – ABSTRACT
Efectul izolației termice a îmbrăcămintei asupra confortului termofiziologic al lucrătorilor
din mediul rece artificial
Studiul de față prezintă efectul izolației termice a îmbrăcămintei asupra confortului termofiziologic al lucrătorilor din
mediul rece artificial. Diferite tipuri de mediu rece artificial din industria alimentară au fost identificate, împreună cu
activitatea lucrătorilor. Pentru evaluarea expunerii la rece și a izolației îmbrăcămintei necesare pentru starea de confort
termofiziologic, a fost calculat Indicele de Izolație termică a îmbrăcămintei (IREQ). Pe baza comparației cu nivelul utilizat
al izolației termice a îmbrăcămintei (2,5 clo), au fost determinați indicele de expunere cu durată limitată (DLE) și timpul
de recuperare (RT). Diferite condiții ale mediului cald, în care lucrătorii trebuiau să se recupereze din cauza expunerii
la rece, au fost, de asemenea, testate: temperatura mediului ambiant, izolația termică a îmbrăcămintei și activitatea.
Rezultatele obținute sugerează strategii de gestionare a expunerii la rece a lucrătorilor din industria alimentară, în
legătură cu activitatea, izolația termică a îmbrăcămintei și condițiile de mediu.
Cuvinte-cheie : izolația termică a îmbrăcămintei, confort termofiziologic, mediu rece artificial
The effect of clothing insulation on the thermophysiological comfort of workers in artificial cold environment
The present study deals with the effect of the clothing insulation on the thermophysiological comfort of workers in
artificial cold environment. Different types of artificial cold environment, related to food industry, have been identified,
together with the activity of the workers. For the assessment of the cold exposure and the clothing insulation needed for
the state of thermophysiological comfort, the Required Clothing Insulation (IREQ) index was calculated. On the basis of
comparison with the used level of clothing insulation (2.5 clo), the Duration Limited Exposure (DLE) index and Recovery
Time (RT) were determined. Different conditions of the warm environment, where the workers had to recover from the
cold exposure, were also tested: temperature of the environment, clothing insulation and activity. The results obtained
suggest strategies for management of the cold exposure of workers in the food industry, related to their activity, clothing
insulation and environmental conditions.
Keywords: clothing insulation, thermophysiological comfort, artificial cold

it presents a method for assessment of the clothing
insulation, needed to protect the human body in low
temperatures. IREQ was developed by Holmér and
included in the ISO Technical Report [3–4]. Later on
it was proposed in ISO 11079 as a tool for designing
and management of the activities in cold environment
[5].
IREQ index is used to assess the cold stress of the
human body on two levels: neutral and minimal [5].
The neutral value of IREQ corresponds to the ther-
mophysiological comfort of the human body, when a
thermal equilibrium between the generated by the
body heat and the heat losses to the environment
exists [6]. The minimal value of IREQ corresponds to
the situation when cold strain already appears, the
body is constantly cooling, but the thermoregulatory
system of the body still can react and maintain the
core body temperature within the desired limits.
Several researchers have investigated different prob-
lems related to thermal comfort or contributed to the
development and application of the IREQ index
[7–16]. The main reason is that extreme temperature
of the environment can provoke injuries, decrease
the working performance and create overall dissatis-
faction [17]. The Unsafe Behaviour Index (UBI), which
gives a relationship between the workers behavior
and the thermal environment, was defined in [18]. It
was found that the risk behavior is minimal within the
temperature interval 17–23°C, while beyond these
limits the proportion of unsafe workers’ behaviour
increases. Obviously, the cold artificial environment
is a risk factor, and appropriate clothing must be used
to decrease its negative influence on workers’ perfor-
mance and health, as well as on workers efficiency at
the workplace.
The aim of the present study was to identify cold-
exposed work places, related in general to food
industry (food production, storage and selling) and to
assess the working environment from the point of
view of the clothing insulation of the protective
ensembles used, the performed activity, the expo-
sure to the cold environment, and the time and con-
ditions needed for recovering of the body from the
cold strain. The performed analysis gives recommen-
dations for the adequate protective clothing insulation
and recovery for different working loads and expo-
sure times. The results obtained suggest strategies
for management of the cold exposure of workers in
the food industry, related to their activity, clothing
insulation and environmental conditions.
EXPERIMENTAL WORK
Identification of artificial cold environment in
food industry
During a preliminary survey on the work-places in
food industry different types of artificial cold environ-
ment have been identified, dependent on the foods to
be processes and the stage of their storage [19–23].
The cold-related work-places and the characteristics
of the cold environment (temperature and humidity)
are summarized in table 1.
Identification of activity level
Four levels of activity were identified in the cold work-
ing environment for food processing and storage:
standing, standing with light activity, slow walking, and
fast walking. The metabolic rates per activity, taken
from ISO 8996:2004 are summarized in table 2 [24].
Clothing insulation
The literature survey has shown that there is no sys-
tematic study on clothing insulation levels of protec-
tive clothing, used in the artificial cold environment of
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COLD RELATED WORK PLACES IN FOOD INDUSTRY
Type of coldenvironment Temperature, oCHumidity, % Application
Cooling warehouse 0 80 ÷ 85 meat, poultry, fruits, vegetables
Freezer warehouse –18 ÷ –23 85 ÷ 90 meat, poultry, frozen eggs, vegetables
Freezer warehouse –20 ÷ –30 90 ÷ 95 fish, sea food, ice cream
Refrigerated warehouse for cooled food 12 85 ÷ 90 bananas
Refrigerated warehouse for cooled food 0 ÷ 8 85 ÷ 90 fruits, vegetables
Refrigerated warehouse for cooled food –2 ÷ 0 80÷85 fresh eggs
Refrigerated warehouse for cooled food –4 ÷ –10 85 ÷ 90 ice cubes
Refrigerated warehouse for cooled food –15 ÷ –20 85 ÷ 90 frozen meat, frozen poultry, frozen
fruits, frozen vegetables
Refrigerated warehouse for cooled food –18 ÷ –23 85 ÷ 90 frozen fish, frozen sea food
METABOLIC RATES PER ACTIVITY
IN THE ARTIFICIAL COLD ENVIRONMENT
Metabolic rate Activity
W/m2met
70 1.2 Standing, immobile
93 1.6 Light activity in upright position,
electric car driving
110 1.9 Walking with 2 km/h
200 3.4 Walking with 5 km/h
Table 1
Table 2

different types of refrigerated warehouses, cooling
warehouses and freezer warehouses. However,
there are studies on the work in cold environment
(both artificial and natural), which deal with the cloth-
ing insulation levels [7–9, 16–17]. It has been found
that a clothing insulation of up to 1.5 clo is carefully
selected by the workers, exposed to artificial cold
(from –30°C to +10°C), while for temperatures of
–20°C and below it is difficult for the workers to
increase the clothing insulation if it is higher than
2.0 clo [7].
The study has reported three different clothing insu-
lation values, used for protection of workers in the
petroleum industry: from 1.7 to 2.6 clo, needed for
exposure in outdoor cold environment from 0 °C
to –34°C [25]. The working conditions in several
Portuguese supermarkets were investigated through
IREQ analysis, field studies and questionnaire stud-
ies [16]. It was reported an average value of the pro-
tective clothing insulation between 1.02 and 1.55 clo,
for a temperature interval of the working conditions
from –17.4°C (freezing chamber) to +12°C (food pro-
cessing workplaces).
A clothing ensemble for cold protection with an insu-
lation value Icl of 2.5 clo was selected to perform the
present analysis. The thermal insulation was inten-
tionally chosen to be on the upper possible limit
(from ergonomic point of view). The idea was to over-
come the wide-spread understanding to suggest
clothing with higher insulation when the temperature
of the working environment is low, as in many cases
even the most insulating ensembles cannot guaran-
tee thermophysiological comfort of the worker.
Therefore, when the increment of the clothing insula-
tion is exhausted, other strategies for ensuring the
human thermophysiological comfort have to be
applied, which will be shown below. The selected
ensemble was a composition between a clothing
ensemble for outdoor and indoor activities [16, 25]. It
was selected to include underwear (underpants and
a long sleeves shirt) from wool with Lenzing FR®
cellulose fibers (50/50%); 3-layers overall with
GORE-TEX® membrane, highly insulated jacket with
GORE-TEX® membrane, calf-length woolen socks,
hard-soled shoes, polar (polyethylene terephthalate)
fleece gloves and a hat.
Calculation of IREQ, DLE, RT
The protocol for calculation of the Required Clothing
Insulation (IREQ), given in ISO 11079, was applied to
build a software code, using Pascal programming
language [5]. The simulation of the IREQ index
required the following initial and boundary conditions
to be used:
– air temperature, air humidity;
– air velocity;
– activity level (metabolic heat production);
– thermal insulation of the clothing ensemble used.
The IREQ index was calculated using eq. (1):
tsk – tcl
IREQ = (1)
R + C
where tsk is the mean skin temperature, °C; tcl is the
temperature of the clothing surface, °C; Rare the
heat loses due to radiation, W/m2; Care the heat
loses due to convection, W/m2, and Sis the body
heat storage rate, W/m2.
Since both IREQ index and the temperature of the
clothing surface are unknown, eq. (1) was solved
together with the general balance eq. (2) using itera-
tions:
M – W – Eres – Cres – E – K – R – C – S = 0 (2)
where Mis the metabolic rate, W/m2; Wis the effec-
tive mechanical power, W/m2; Eres are the heat loss-
es due to respiration, W/m2; Cres are the respiratory
convective heat losses, W/m2; Eare the heat losses
due to evaporation, W/m2; Kare the heat losses due
to conduction, W/m2.
Two values of IREQ were calculated: IREQneutral,
which corresponds to the state of thermophysiologi-
cal comfort of the person, and IREQmin, which is
related to all other cases when the clothing still can
protect the body, but it is already in a state of contin-
uous cooling.
Eleven temperature regimes were identified, follow-
ing the working conditions in food warehouses,
described in table 1: from +12°C to –28°C with a step
of 4°C. The relative humidity was set to 85% for all
cases. The two values IREQneutral and IREQmin were
compared with the thermal insulation of the clothing
ensemble (2.5 clo) and the Duration of Limited
Exposure to cold environment (DLE index) was
determined.
DLE index was calculated using eq. (3):
Qlim
DLE = (3)
S
where Qlim is the limit value of body heat gain or loss,
kJ/m2, and Sis calculated from eq. (1).
Two values of DLE index were calculated: DLEmin,
which corresponded to IREQmin, and DLEmax, which
corresponded to IREQneutral. When the predicted
exposure time to cold environment was less than one
working shift (DLE < 8 hours), than Recovery Time
(RT index) was predicted.
RT index was used to assess the needed environ-
mental conditions and period for rest, so as the work-
ers to be able to continue their work in the cold envi-
ronment without a danger from cold injuries and
appearance of negative behavior. RT was calculated
using eq. (3), substituting the conditions of the cold
environment with the conditions for resting in warmer
environment: Qlim
RT = (4)
S
DLE and RT were calculated following the mathe-
matical model and protocol, given in ISO 11079 [5].
RESULTS AND DISCUSSIONS
Figure 1 presents the results from calculation of the
Required Clothing Insulation for the respective tem-
perature and humidity of the artificial cold environment
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(see table 1) and 4 levels of activity (see table 2).
IREQmin , and IREQneutral were determined for each
case of cold exposure.
The results show that as lower the temperature and
the metabolic values are, as higher the required insu-
lation of the clothing ensemble must be. The thermo-
physiological comfort (IREQneutral) of a sitting person
with the selected protective clothing will be guaran-
teed for up to 8°C. In colder environment (4°C) a
cooling of the body will appear (IREQneutral > Icl). If
the person has to continue his work in the environ-
ment of 4°C, three strategies for management of the
cold exposure of the worker are possible:
● additional clothing item must be added so as to
increase the clothing insulation Icl to 2.9 clo (to
reach IREQneutral) or
● the exposure in the cold environment to be
reduced from 8 hours to limited exposure time
(DLE index must be calculated) or
● the metabolic activity has to increase.
The increment of the metabolic rate from standing
(70 W/m2) to light activity in upright position (93
W/m2) guarantees the thermophysiological comfort of
the worker in 0°C, up to –4°C, when a cooling of the
body will start. The new increment of the activity
through slow walking (110 W/m2) will allow the work-
er to remain in thermophysiological comfort in cold
environment of up to –8°C. The cooling of the body,
which starts at –8°C, will require more heat to be pro-
duced by the body through activity (muscle work).
The last tested metabolic rate of 200 W/m2(fast walk-
ing in the cold environment) allows the human body
to be in a thermophysiological comfort in all investi-
gated regimes of cold environment (see table 1), up
to –28°C (in freezer warehouses).
The analysis of the results from the calculation of the
IREQ index shows that the work in standing, immo-
bile position (i.e. monitoring of a process) must be
avoided in the cold environment. The standing pos-
ture has to be combined at least with light activity or
slow walking. Fast walking is advisable for workers
who enter periodically the warehouse. It is also advis-
able for workers in freezer warehouses where the
temperature is below –20°C.
Figure 2 summarizes the results from the calculation
of Duration Limited Exposure index (DLE). Both the
minimum DLEmin and the maximum DLEmax time of
exposure in the cold environment were calculated,
taking into account the activity. The results show that
the activity strongly influences the effect of the cold
exposure, when the same clothing insulation level Icl
is used: in a standing position the generated heat
from the body is able to ensure the thermophysiolog-
ical comfort during full working shift (8 h) in a cold
environment with a temperature of up to +4°C. The
generated heat during slow walking can ensure
continuous work (8 h) in a temperature of –8°C. If the
worker walks with 5 km/h, then 2.5 clo is enough to
ensure the thermophysiological comfort of the body
even in freezer warehouses with temperature of
–28°C.
The analysis of the results in figure 2 shows that if the
insulation of the clothing ensemble cannot be
increased (as in this case), due, for example, of awk-
ward movements or other ergonomic reasons, than
the strategy for management of the cold exposure is
to increase the activity in the cold work-place.
However, the activity may provoke sweating, which
lead to augmentation of the heat loses by evapora-
tion. This would negatively influence the thermophys-
iological comfort of the worker, due to appearance of
faster cooling. Therefore the combination between
the clothing insulation and the activity must be care-
fully selected and a feedback from the workers must
be received (i.e. via questionnaire studies for thermal
comfort evaluation).
If the clothing insulation is not high enough to protect
the human body from cold and to ensure the thermo-
physiological comfort, the strategy for management
of the cold exposure is to interrupt the exposure in
the cold and a period for recovery of the body in
warm indoor environment to be secured. ISO 11079
does not deal with the conditions for recovery of the
body from the cold exposure, however [5].
The present study tested different cases of “warm
exposure” during the recovery period from the cold.
The temperature of the warm environment was
increased from 18°C to 30°C, with a step of 2°C (the
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Fig. 1. Required clothing insulation for working in
temperature interval (+12°C ÷ –28°C), four levels of activity
Fig. 2. Duration of limited exposure for working in
temperature interval (+12°C ÷ –28°C), four levels of activity

relative humidity of the environment was kept con-
stant, 60%). Two body postures were considered
during resting: seated relaxed (1 met, 58 W/m2) and
standing relaxed (1.2 met, 70 W/m2). Two values of
clothing insulation were also used for the calcula-