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179
Tekstilec, 2018, 61(3), 179-191
DOI: 10.14502/Tekstilec2018.61.179-191
Corresponding author/Korespondenčni avtor:
Jawad Naeem
E-mail: jawadnaeem.qau@gmail.com
Jawad Naeem, Adnan Mazari, Funda Buyuk Mazari, Zdenek Kus, Jakub Weiner
Technical University of Liberec, Studentská 1402/2, 46117 Liberec, Czech Republic
Comparison of Thermal Performance of Fire ghter
Protective Clothing at Di erent Levels of Radiant Heat
Flux Density
Primerjava učinkovitosti toplotne zaščite oblek za gasilce pri
različnih stopnjah sevanja toplotnega toka
Original Scienti c Article/Izvirni znanstveni članek
Received/ Prispelo 04-2018 • Accepted/ Sprejeto 08-2018
Abstract
The experimental work presented in this study is related to the investigation of thermal protective perfor-
mance of fi refi ghter clothing, which plays a pivotal role in the fi refi ghters’ safety and performance. The fi refi gh-
ter clothing usually consists of three layers, i.e. an outer shell, moisture barrier and thermal liner. Four sam-
ples were used for the purpose of this study. The samples were characterized on Alambeta for the evaluation
of thermal resistance and thermal conductivity, respectively. Afterwards, the samples were evaluated on a
thermal manikin “Maria” at room temperature to measure the insulation values. Moreover, air permeability
was evaluated by using an air permeability tester. The samples were then analysed for their thermal protec-
tive behaviour in line with a lightly modifi ed ISO standard 12127, i.e. the samples were subjected toa150 °C
heat plate at constant speed. In addition, transmitted heat fl ux density and percentage transmission factor
of all samples were determined with the help of a radiant heat fl ux density machine at 10 kW/m2 and 20
kW/m2. It was concluded that sample 4 had higher thermal resistance and insulation values. The outer shell
of sample 4 had lower air permeability values as compared to the outer shell of samples 1, 2 and 3. Similar-
ly, the combination of the outer shell 4 and the thermal barrier 4 led to lower air permeability values as com-
pared to the combination of the outer shell 1 and thermal barrier 1, outer shell 2 and thermal barrier 2, and
outer shell 3 and thermal barrier 3. The rate of temperature rise in sample 4 occurred at a slower rate against
the heated plate in comparison with samples 1, 2 and 3. Furthermore, sample 4 exhibited lower transmitted
heat fl ux density and percentage transmission factor as compared to samples 1, 2 and 3.
Keywords: multilayer protective clothing, thermal radiation, radiant heat transmission index, fl ame
Izvleček
Raziskava je bila osredotočena na učinkovitost toplotne zaščite oblek za gasilce, ki je ključnega pomena za varnost
in učinkovito delo gasilcev. Oblačila za gasilce običajno sestavljajo tri plasti, tj. zunanja plast, paroprepustna plast in
toplotnoizolacijska plast. V raziskavo so bili vključeni štirje vzorci. Z Alambeto so bile značilne lastnosti vzorcev za
oceno toplotnega upora oziroma toplotne prevodnosti. Nato so bile pri sobni temperaturi določene izolacijske vre-
dnosti na toplotni poskusni lutki »Mariji«. Ovrednotena je bila tudi zračna prepustnost vzorcev na aparatu za prepu-
stnost zraka. Vzorci so bili nato analizirani z vidika sposobnosti toplotne zaščite s pomočjo nekoliko spremenjene
standardne metode ISO 12127 z izpostavitvijo vzorcev temperaturi do 150 °C na toplotni plošči pri konstantni hitro-
sti. S pomočjo sevalne naprave pri toplotnih tokih 10 kW/m2 in 20 kW/m2 sta bila določena tudi prenos toplotnega
toka ter faktor prenosa vseh vzorcev. Ugotovljeno je bilo, da ima vzorec 4 visok toplotni upor in toplotno izolativnost.
Zunanja plast vzorca 4 je imela nižje vrednosti zračne prepustnosti kot zunanje plasti vzorcev 1, 2 in 3. Podobno je v
primerjavi z vzorci 1, 2 in 3 imela kombinacija zunanje plasti skupaj s toplotnoizolacijsko plastjo vzorca 4 nižjo
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Tekstilec, 2018, 61(3), 179-191
Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
1 Introduction
Clothing not only serves as a barrier to the exterior
atmosphere but also acts as a heat transmission chan-
nel from the human body to the surrounding atmos-
phere [1]. A microclimate is generated by the cloth-
ing between the human skin and air layer, which
assists the thermoregulatory mechanism of the hu-
man body to maintain its temperature within a safe
limit, despite the exterior environmental tempera-
ture and humidity deviating to some degree [2‒4].
e exchange of heat in clothing includes conduc-
tion via the air gap and fabric layer, convection of the
air gap and radiation from the fabric layer to another
fabric layer [5]. In some situations, protection against
ame and heat becomes primary precedence for a
speci c area of applications like re ghting, where a
shield against ame and thermal insulation is re-
quired [6]. e re ghters’ lives are always in contin-
ual danger when they are subjected to an escalated
temperature climate, high thermal radiation, interac-
tion with hot objects and confrontation to several
types of flame, flash over being the most dangerous
[7]. e re ghter protective clothing shields the
re ghter from hazards like spilling of chemicals,
ame, external radiant heat ux, and o ers a thermal
equilibrium to their body [8]. e re ghter protec-
tive clothing consists of three layers, i.e. an exterior
shell, moisture barrier and thermal liner [8‒10]. e
exterior shell is made up of the substrates which do
not burn or degenerate when they are confronted
with the heat and ame. ese materials avert igni-
tion when they are in contact with ame, and must
be water repellent and permeable to water vapour.
Generally, the outer shell is made up of meta-aramid
(Nomex), and a combination of meta-aramid and
para-aramid (Nomex III A), polybenzimidazole
(PBI), Zylon. Sometimes, ame resilient nishes like
Proban and Pyrovatex are employed as well. e
moisture barrier is a microporous or hydrophilic
membrane situated between the thermal liner and
outer shell. is membrane is permeable to water va-
pour but impermeable to liquid water, and protects
the human body from blood pathogens and chemi-
cals in liquid form. is membrane is accessible in
market as Gore-Tex, Proline and Cross tech, Action
and Neo guard. e thermal liner secures the human
body by delaying the external environment heat. It is
made up of ame retardant bres and their blends.
ey can be non-woven, laminated woven, quilted
batting and spun laced [10‒12]. e schematic dia-
gram of a multilayer assembly is shown in Figure 1.
Time is the main factor when the thermal protec-
tive performance is evaluated. An escalation in the
thermal protective performance (TPP) means an in-
crement in the duration of time for re ghters to
conduct their duties without enduring any severe
skin burn injuries. Consequently, more time can be
spent by the re ghter to save lives and prevent
damages instigated by re and heat [14‒16].
Figure 1: Con guration of multilayer protective cloth-
ing [10, 13]
I – outer shell, II – moisture barrier, III – thermal liner
Factors like thermal conductivity, water vapour re-
sistance, volumetric ow capacity, permeability in-
dex and e ect of air gaps can have an impact on the
thermal protective performance of re ghters’
clothing (FFC) [17]. e evaluation of TPP can be
performed by several tests (heat guard plate, TPP
tester) [18‒22] or the full-scale testing method
(thermal manikin) [23‒24].
A lot of scienti c research in the form of numerical
models and experimental studies has been conduct-
ed under various levels of radiant heat ux density to
evaluate the thermal protective performance of FFC.
ese studies have made use of the test methodolo-
gies like bench scale testing and full manikin test to
determine the thermal protective performance of
FFC under various levels of radiant heat exposure.
e aim of this study was to investigate the thermal
protective performance of di erent FFC samples.
vrednost zračne prepustnosti. Prav tako je temperatura v vzorcu 4 na grelni plošči naraščala počasneje kot v vzorcih
1, 2 in 3. Vzorec 4 je imel tudi nižji prenos toplotnega toka in nižji faktor prenosa v primerjavi z vzorci 1, 2 in 3.
Ključne besede: večplastna varovalna obleka, toplotno sevanje, faktor prenosa sevane toplote, ogenj
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Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
Four di erent sample arrangements were made.
ese samples were tested with Alambeta, thermal
manikin Maria and air permeability tester FX 3300.
e threshold time, t (s), was measured in accord-
ance with the ISO 12127 standard. A erwards, these
samples were characterized with a radiant heat
transmission machine (ISO 6942 method) to de-
termine the heat transmission through a sample at
10 kW/m2 and 20 kW/m2. Moreover, transmitted
heat ux density, Qc (kW/m2), percentage transmis-
sion factor, %TF(Qo) and radiation heat transmis-
sion index (RHTI12 and RHTI24) were determined.
2 Experimental
2.1 Materials
All re ghter clothing (FFC) was provided by Vo-
choc Ltd Czech Republic). Each clothing item con-
sisted of three layers, i.e. outer layer, moisture barri-
er and thermal liner. Four di erent clothing items
with di erent material combinations were used in
this research. e material speci cations taken from
re ghter clothing items (Table 1) and their ar-
rangement in the clothing assembly are listed below
(Table 2).
Table 1: Material speci cations
Material
code Material speci cation Material
function Weave Mass per unit
area [g/m2]
O1 55% Conex, 38% Lenzing FR, 5% Twaron,
2% Beltron
Outer shell Rip stop 215
MB1 Fabric:100% polyester
TOPAZ high tech PU
Moisture
barrier
Non-woven 145
TB1 ermo: para-aramid
Liner: 50% meta-aramid, 50% viscose
ermal liner Non-woven 200
O2 75% Nomex, 23% Kevlar, 2% P-140 Outer shell Rip stop 195
MB2 Fabric: 50% Kermel, 50% viscose FR
PTFE membrane
Moisture
barrier
Non-woven 120
TB2 ermo: para-aramid
Liner: 50% meta-aramid, 50% viscose
ermal liner Non-woven 200
O3 55% Conex, 38% Lenzing FR, 5% Twaron,
2% Beltron
Outer shell Rip stop 215
MB3 Fabric: 50% Kermel, 50% viscose FR
PTFE membrane
Moisture
barrier
Non-woven 120
TB3 ermo: para-aramid
Liner: 50% meta-aramid, 50% viscose
ermal liner Non-woven 200
O4 70% Conex, 23% Lenzing FR, 5% Twaron,
2% Beltron
Outer shell Rip stop 225
MB4 Fabric: 50% Kermel, 50% viscose FR
PTFE membrane
Moisture
barrier
Non-woven 120
TB4 ermo: para-aramid
Liner: 50% meta-aramid, 50% viscose
ermal liner Non-woven 200
Table 2: Sample speci cations
Sample No. Sample assembly ickness [mm] Mass per unit area [g/m2]
1 O1 + MB1 + TB1 2.636 560
2 O2 + MB2 + TB2 2.703 515
3 O3 + MB3 + TB3 2.759 535
4 O4 + MB4 + TB4 2.77 545
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Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
2.2 Methods
2.2.1 Alambeta
Alambeta is a computer-controlled non-destructive
device. With the help of Alambeta, the thermal
properties of single layer and multilayer fabrics are
determined [25‒27]. It is non-destructive equip-
ment which comprises of a movable hot plate at-
tached to an ultrathin heat ow sensor on the top
side and a lower cold plate. is upper heated plate
falls in downward direction and makes a contact
with the surface of the sample which is placed on
the lower cold plate. e computer records the heat
ow due to the di erentiation in temperature be-
tween the upper heated plate and the sample on the
cold plate. e temperature of the upper plate is
held at 32 °C, where as the lower plate is kept at am-
bient temperature, i.e. at around 20 °C. With the
help of Alambeta, characteristics like thermal con-
ductivity, thermal di usivity, thermal absorptivity,
thermal resistance, sample thickness, and heat ow
density and heat ow density ratio can be deter-
mined [28‒29]. In this research, each sample was
evaluated ve times.
2.2.2 Thermal manikin
A thermal manikin Maria (Figure 2) was used to
measure the thermal insulation values of re ghter
protective clothing samples. e manikin is built up
of bre glass armed polyester shell covered with a
thin nickel wire enveloped around the body to en-
sure the heating and temperature measurement. e
design of shoulder, hip and knee joints was made of
a circular cut to make the sitting and standing posi-
tions normal.
Figure 2: ermal manikin Maria with le forearm
covered with sample of re ghter protective clothing
During the testing, the manikin was positioned at
the centre of the climatic chamber and was kept in a
supporting frame, hung from the head and with the
feet 0.15 m away from the oor. e manikin had
20 independent parts managed by a computer ac-
cording to the association between dry heat losses
and skin temperature of the human body for the
conditions close to thermal comfort [29].
In our experiment, the forearm limb portion of the
manikin was covered with a forearm sleeve, since
the forearm limb area was much lesser as compared
to the other parts of the manikin where less fabric
was used.
Global method
e global method is a general formula for de ning
the whole body resistance. It is a conventional meth-
od which performs an overall calculation and de-
nes whole body resistance. In equation1, f1 is the
relationship between the surface area of the segment
I of the manikin, Ai, and the total surface area of the
manikin, A. To is the temperature of the operating
environment in degrees centigrade (°C). T
–
sk is the
mean skin temperature in °C and .
Q
–
s,i is the sensible
heat ux acquired by area weighing (W/m2). First,
the thermal insulation of a nude manikin, Ia, was
calculated.
IT = ∑(fi × T
–
sk,i) – T0
∑(fi × .
Q
–
s,i) (1)
A er subtracting Ia from IT , the e ective clothing
insulation, Icle, (m2 °C/W) was acquired.
Icle = IT – Ia (2)
To calculate the intrinsic thermal insulation, Icl was
calculated with equation 3:
Icl = IT – Ia
fcl (3),
where fcl is the ratio of the outer surface area of a
clothed body to the surface area of a nude body.
2.2.3 Air permeability
An air permeability tester FX3300 Labotester III
(Textest Instruments) was utilized to evaluate air
permeability in line with the CSN EN ISO 9237
standard. e test pressure was 200 Pa on the area
of 20 cm2 (l/m2/s). Ten measurements were per-
formed for each sample according to the standard.
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Tekstilec, 2018, 61(3), 179-191
Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
2.2.4 Contact heat plate test
e contact heat plate test was used to characterise
the thermal protective performance of re ghter
protective clothing. An experimental setup was
made, the basic principle deriving with a slight
modi cation from the ISO standard12127 [30].
e hot plate was heated to and maintained at con-
stant temperature, and a thermocouple was placed
on the top of a test sample. e sample was lowered
down towards the heated cylinder. e operation
was conducted at constant speed. e threshold
time was evaluated by monitoring the temperature
rise of the thermocouple.
e samples of FFC were cut to 15 cm diameter and
then attached on to a ring shape frame. e latter
was made xed on a circular clamp with the help of
a magnet and thermocouple on the top and middle
of a sample. e clamp was attached to a dynamom-
eter. e heated plate (heat source) was maintained
at constant temperature of 150 °C, as the re ghter
protective fabric test samples were made up of me-
ta-aramids, which has maximum continuous tem-
perature usage at 150 °C. A schematic diagram is
shown in Figure 3. e samples were raised to the
height of 60 mm above the heated plate with the
help of a dynamometer and a erwards brought
down towards the heated plate. When the distance
between the heat plate and the sample was 10mm,
we recorded the time and noted the temperature of
the sample until there was a 10 °C rise in tempera-
ture. A erwards, we removed the heat source away
from the sample and allowed the thermocouple and
clamps to cool down for the next sample to be eval-
uated. e samples were brought towards the heat-
ed plate at the constant speed of 5mm/min [30]. e
test procedure had to be performed on three sam-
ples to get the average value. e arrangement of the
contact heat test is depicted in Figure 4.
e apparatus consists of a heat plate, digital multi-
meter, T type thermocouple, clamps and a dy-
namometer:
Heat plate which is VWR
• ® professional hot plate
developed for applications requiring exceptional
accuracy, stability, and repeatability are equipped
with an exclusive safety system that helps protect
both the operator and sample.
Digital multimeter Velleman DVM 345DI was
•
employed to evaluate the temperature changes in
the sample. is device enables the user to mea-
sure AC and DC voltages, AC and DC currents,
resistance, capacitance and temperature. e de-
vice can be interfaced with a computer and the
user can also test diodes, transistors and audible
continuity.
T type thermocouple “UT-T” with the tempera-
•
ture probe test range from –40 to +260 °C with
the accuracy of ±0.75% was utilized. Circular
clamps were employed to hold the sample.
Dynamometer was used to move the test sample
•
at the constant speed of 5 mm/min from xed di-
stance.
Figure 3: Schematic diagram of contact heat test ar-
rangement
Figure 4: Arrangement of contact heat test
2.2.5 Transmission of radiant heat fl ux density
e equipment consists of a radiation heat source,
which can generate heat ux density of up to 80
kW/m2 along with a calorimeter to determine the
radiant heat ux density.
e ISO 6942 standard was employed to measure
the transportation of heat through a single layer and
Dyna-
mometer
Dyna-
mometer
Spe-
cimen
fi xed in
clamp
Clamps
T
Thermo-
couple
Sample
Load cell
Heat pla-
te at tem-
perature
of 150 °C
10 mm
Hot plate
at 150 °C
Load cell
Voltmeter
T
Thermo-
couple
mple
184
Tekstilec, 2018, 61(3), 179-191
Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
multilayer FFC sample. e sample dimension was
230 mm × 80 mm. All samples had to be condi-
tioned for at least 24 hours at the temperature of
20±2 °C and had relative humidity of 65±2% [31].
e apparatus included a curved copper plate calo-
rimeter placed on a non-combustible block. e
front face of the calorimeter was layered with a thin
lm of black paint with the absorption coe cient
“a” greater than 0.9. e heating device comprised
of six carbide rods, a moving frame assembly which
was constantly cooled by a passage of water in cool-
ing pipes and a removable screen. e rst step
started with calibration, the position of the calorim-
eter was adjusted and then the calorimeter was ex-
posed to the heating rods and the movable screen
was withdrawn and returned to its original position
when the temperature escalation reached 30 °C. e
incident heat ux density, Q0, was measured. Later
on, the sample was a xed to one side of the plate of
the sample holder and held in contact with the face
of the calorimeter, applying the mass of 200 g. e
movable screen was withdrawn and the starting
point of the radiation head was noted. e movable
screen was returned to its closed position a er the
temperature rise of about 30 °C. e time t12was to
achieve the temperature rise of 12.0±0.1 °C and the
timet24to achieve the temperature rise of 24±0.2 °C
in the calorimeter, expressed in seconds, deter-
mined to the nearest 0.1 s. At least three samples
had to be tested to get the average value [31]. Figure
5 shows the arrangement of the radiant heat testing
equipment.
Figure 5: Radiation heat testing equipment
e conclusion of the experimentation led to two
threshold times, i.e. radiant heat transfer index (RH-
TI12 and RHTI24), transmitted heat ux density (Qc)
and percentage heat transmission factor %TF(Qo)
e transmitted heat ux density, Qc, in kW/m2 was
calculated with the following equation:
Qc = MCp
A × K (4),
where M (kg) is the mass of the copper plate, Cp is
the speci c heat of copper 0.385 kJ/kg°C, A(m2) is
the area of the copper plate, K (°C/s) is the mean
rate of temperature rise in the calorimeter in the re-
gion12–24 °C rise.
K = 12
RHTI24 – RHTI12 (5),
where RHTI12 indicates the time (s) required for the
temperature rise of 12±0.1 °C, and RHTI24 means
the time for the temperature rise of 24±0.2 °C in the
calorimeter.
e percentage heat transmission factor, %TF(Qo),
for the incident heat ux density level was deter-
mined with equation 6.
%TF(Q0) = Qc
Q0 × 100 (6),
where Q0 is the incident heat ux density (equation 7).
Q0 = CpRM
a A (7),
where R (°C/s) is the rate of the calorimeter temper-
ature rise in the linear region and a is the absorption
coe cient of the painted surface of calorimeter.
3 Results and discussion
3.1 Evaluation of thermal properties
e thermal insulation of protective clothing plays a
very important role in the thermal protective per-
formance of re ghter protective clothing. e main
purpose of re ghter protective clothing is to delay
the increase in temperature of the human body when
they are exposed to a heat source and consequently
to enhance the re ghters’ working time when sav-
ing lives and valuables. e ability of a textile sub-
strate to conduct heat is called thermal conductivity
of a textile material. A greater value of thermal con-
ductivity indicates a greater amount of heat exchange
passing through that substrate. However, the thermal
conductivity of a textile substrate is determined by
the physical and chemical properties of the textile
substrate [32]. An increment in the relative humidity
absorbed by the substrate is followed by an increase
in the thermal conductivity of the textile substrate
Carbide
heating rods Specimen fi xed on
face of calorimeter
Clamp
Cooling
system Movable
frame
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Tekstilec, 2018, 61(3), 179-191
Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
[34]. Consequently, the more a material is hygroscop-
ic, the better is thermal conductivity. ermal resist-
ance is associated with thickness, surface weight and
density. For thickness, it can be explained that at
equivalent surface weights, increasing the thickness
leads to an increase in the amount of air entrapped in
the fabric. is is con rmed by the fact that thermal
resistance decreases by increasing density as higher
density means less air entrapped in the textile. In
consequence, a thick fabric has higher thermal resist-
ance as compared to a light and thin textile substrate
[33]. is is also described by the mathematic formu-
la: R= h/λ, where R is thermal resistance, h is thick-
ness and λ thermal conductivity. Moreover, it is in u-
enced by the fabric construction parameters. us, a
thick and heavy fabric is more insulative than a thin
and light one [35]. Table 1 reveals that sample 4 had
slightly greater thickness than other samples, which
might be one reason for better thermal insulation
and increased thermal resistance as compared to oth-
er samples. As the thickness of sample 1 was smaller
than the rest of samples, sample 1 had signi cantly
lower values of thermal resistance and total thermal
insulation, and clo values as compared to the rest of
samples. is was also evident by the ANOVA test as
the p-value was 7.35×10–5, i.e. less than 0.05, indicat-
ing a signi cant di erence among the samples. Fur-
thermore, the constituent material of the substrate
plays a very important role in the thermal insulation/
thermal resistance of re ghter protective clothing
[36]. e results of Alambeta in Figure 6 also support
the outcomes (insulation and clo values) in Figures 7
and 8 for the thermal manikin, i.e. greater thermal
insulation, which results in lower thermal conductiv-
ity and enhanced thermal resistance.
Figure 7: Total thermal insulation (IT), e ective cloth-
ing insulation (Icle) and basic insulation (Icl) of re-
ghter protective sample
Figure 8: Total clothing insulation (IT), e ective clothing
insulation (Icle) and basic clothing insulation (Icl) in clo
3.2 Evaluation of air permeability
As the air permeability of the moisture barrier in
re ghter protective clothing is zero, the evaluation
of the air permeability of the outer shell and outer
shell + thermal barrier was conducted. e air per-
meability of re ghter protective clothing is very
low, since the main task of re ghter protective
clothing is to protect the re ghter’s body from the
heat in the form of radiation, convection and con-
duction. If the value of air permeability is very high,
it decreases the thermal protective performance of
re ghter clothing as it allows the air to pass
through the sample resulting in the temperature in-
crease of the human body within a shorter period of
time. It can be seen in Figure 9 that the outer shell
of sample 4 exhibited lower air permeability values
as compared to the outer shell of samples 1, 2 and 3.
Figure 10 shows that sample 4 had a lower value of
air permeability as compared to the rest of samples
in the case of the outer shell and outer shell + ther-
mal barrier, and this low value is supported by the
high value of thermal insulation and low values of
thermal conductivity as evaluated by the thermal
manikin and Alambeta, respectively.
m2K/W
0.054
Sample 1
Thermal conductivty
(W/mK)
Sample 2 Sample 3 Sample 4
0.04682 0.04596 0.04659 0.0448
0.0563 0.06008 0.05958 0.06115
0.08
0.07
0.06
0.05
0.04
0.03
0.049
0.044
0.039
0.034
0.029
0.024
0.019
0.014
0.009
0.004
W/mK
Thermal resistance
(m2K/W)
Figure 6: Analysis of thermal characteristics with
Alambeta
0.200
0.150
0.100
0.050
0.000 Sample 1
IT (m2°C/W) Icle (m2°C/W) Icl (m2°C/W)
Global method
Global method
Global method
Sample 2 Sample 3 Sample 4
0.168 0.196 0.193 0.198
0.067
0.087 0.095
0.114 0.092
0.111 0.097
0.116
Insulation (m2°C/W)
1.400
1.200
1.000
0.800
0.600
0.400
0.200
0.000 Sample 1 Sample 2 Sample 3 Sample 4
1.086 1.262 1.234 0.277
0.434 0.610 0.591 0.625
0.560 0.736 0.717 0.751
Insulation (Clo)
IT (Clo) Icle (Clo) Icl (Clo)
Global method
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Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
Figure 9: Air permeability of outer shell of re ghter
protective samples
Figure 10: Air permeability of outer shell + thermal
barrier of re ghter protective clothing
3.3 Contact heat plate test at 5mm/min
exposing speed
In Table 3 and Figure 11, it can be seen that sample 4
took more time for the increment of 10 °C rise in tem-
perature when exposed to the heat source (150 °C) at
the constant speed of 5 mm/min. Furthermore, when
the sample was at 10 mm distance from the heat
source, the temperature at the back of sample 4 was
lower as compared to other samples at the same dis-
tance. ere are two possible reasons for better ther-
mal protective performance of the clothing. One is
the thickness and the other is the physical and chem-
ical properties of constituent bres in the fabric. In
the case of sample 4, thickness was slightly higher as
compared to the rest of samples; the sample had a
higher percentage of meta-aramid in the outer shell,
enhancing the thermal protective performance and
delaying the rate of the temperature rise.
e greater the delay in the heat transmission to-
wards the human body, the greater is the thermal
protective performance of the clothing, enabling the
re ghters to spend more time on duty.
Table 3: reshold time in contact heat test at exposing speed of 5mm/min
Sample No. Tc [°C T1 [°C T2 [°C t s]
1 150 49±1 60.3±1.53 91
2 150 44.3±1.15 54.7±0.58 106
3 150 46.7±1.53 58.3±1.53 101
4 150 41.7±0.58 52.7±1.15 111
Tc – contact temperature of hot plate
T1 – initial temperature at the back of sample when at the distance of 10 mm from hot plate
T2 – nal temperature at the back of a sample when there is a 10 °C rise in temperature
t threshold time for increase of 10 °C
Figure 11: Contact temperature and thermal protective performance of re ghter clothing at exposing speed of
5 mm/min
450
400
350
300
250
200
150
100
50
Air permeability (m2/s)
Air permeability
Time (s)
Air permeability
Outershell (1) Outershell (2) Outershell (3) Outershell (4)
424.7 387.6 413.8 358.2
0
350
325
300
275
250
Air permeability (m2/s)
Temperature (°C)
Outershell (1) + TB Outershell (2) + TB Outershell (3) + TB Outershell (4) + TB
323.3 309.3 326 291.5
Exponent (Sample 1) Exponent (Sample 2) Exponent (Sample 3) Exponent (Sample 4)
187
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Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
3.4 Transmission of radiant heat fl ux through
multilayer protective clothing
A generic overview of Table 4 reveals that with the
increase in the value of the incident heat ux density
from 10 kW/m2 to 20 kW/m2, the values of trans-
mitted heat ux density, Qc, (kW/m2) and percent-
age transmission factor %TF(Qo) increase succes-
sively at all samples. On the other hand, a reverse
trend was observed for the values of the radiant heat
transmission index RHTI24 – RHTI12 (s). e small-
er the values of transmitted heat ux density, the
lesser the amount of heat owing through the FFC
sample towards the calorimeter. In consequence,
re ghters are able to continue with their activities
for a lengthier period before acquiring skin burn in-
juries. Table 4 also illustrates that a greater di erence
between RHTI24 (s) and RHTI12 (s) shows that the
sample is able to withstand the respected incident
heat ux density for a longer duration before having
burn wounds.
At Qo of 10 kW/m2, samples 1 and 3 depicted high-
er values of Qc (kW/m2) as compared to samples 2
and 4, respectively. Qc (kW/m2) values of samples 1
and 3 were very close to each other. A slightly dif-
ferent pattern was witnessed for FFC samples at Qo
of 20 kW/m2. Sample 1 depicted very high values of
Qc and %TF(Qo) as compared to all samples. Sam-
ples 2 and 3 exhibited very close values of Qc and
%TF(Qo). However, the lowest value of Qc and
%TF(Qo) was witnessed at sample 4.
Sample 1 had relatively smaller thickness as com-
pared to all other samples due to which it delivered
higher values of Qc and %TF(Qo) at both 10 kW/m2
and 20 kW/m2. In the case of sample 2, it had slight-
ly smaller thickness as compared to samples 3 and 4.
Nevertheless, it had a lower value of Qc and %
TF(Qo) as compared to sample 3. is might be due
to the fact that sample 2 had higher percentage of
meta-aramid in the outer shell, assisting the endur-
ance against radiant heat ux density for a longer
period of time, and delivered lower values of Qc and
%TF(Qo).
Sample 4 had slightly higher thickness and greater
percentage of meta-aramid in the outer shell as com-
pared to the rest of samples due to which the trans-
mission of heat was delayed, and smaller values of
Qc and % TF(Qo) were observed at both 10 kW/m2
and 20 kW/m2.
At Qo of 10 kW/m2, samples 1 and 3 depicted higher
values of Qc (kW/m2) as compared to samples 2 and
4, respectively. e Qc (kW/m2) values of samples 1
and 3 were very close to each other. A slightly dif-
ferent pattern was witnessed for the FFC samples at
Qo of 20 kW/m2. Sample1 depicted very high values
of Qc and %TF(Qo) as compared to all the samples.
Samples 2 and 3 exhibited very close values of Qc
and %TF(Qo). However, the lowest value of Qc and
%TF(Qo) was witnessed at sample 4.
Sample 1 had relatively smaller thickness as com-
pared to all other samples due to which it deliv-
ered higher values of Qc and % TF(Qo) at both 10
kW/m2 and 20 kW/m2. Sample 2 had slightly
smaller thickness as compared to samples 3 and 4.
Never the less, it had a lower value of Qc and
%TF(Qo) as compared to sample 3. is might be a
consequence of sample 2 having greater percent-
age of meta-aramid in the outer shell, assisting the
endurance against radiant heat ux density for a
longer period of time, and delivering a lower value
of Qc and %TF(Qo).
Table 4: Comparison of transmitted heat ux density and incident heat ux density at 10 and 20 kW/m2
Sample
No.
Qo
kW/m2]RHTI12 [s] RHTI24 [s] RHTI24 –
RHTI12 [s] Qc [kW/m2]TF (Qo)
[%]
1 10 34.35±0.919 53.9±0.697 19.55 3.382 33.8
2 37.4±0.282 61±0.424 23.6 2.8022 28.0
3 37.6±1.181 59.4±1.939 21.8 3.033 30.3
4 44.25±0.495 72.9±0.848 28.65 2.308 23.0
1 20 21.95±0.070 31.35±0.141 9.4 7.035 35.1
2 25.9±0.282 38.65±0.353 12.75 5.1868 25.9
3 26.7±1.979 38.35±1.757 11.65 5.676 28.3
4 28.95±0.474 43.3±0.676 14.35 4.608 23.0
188
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Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
Sample 4 had slightly greater thickness and higher
percentage of meta-aramid in the outer shell as
compared to other samples, due to which the trans-
mission of heat was delayed and lower values of Qc
and % TF (Qo) were observed at both 10 kW/m2and
20 kW/m2.
Figure 12 shows that in the rst 12 seconds, the rate
of temperature rise in all samples was almost equal.
However, a erwards, the rate of temperature rise of
sample 4 occurred at a much slower rate; therefore,
a atter curve was seen. In the case of sample1, a
steeper curve was observed, which indicated that
the rate of temperature rise was greater as compared
to the rest of samples. For samples 2 and 3, the
curve pattern was very similar until the 35th second.
A erwards, the curve of sample 2 became slightly
atter as compared to the curve of sample 3, indi-
cating a slightly better thermal protective perform-
ance of sample 2 as compared to sample 3. e at-
ter the curve, the more time was required to rise the
Figure 13: Transmission of heat through FFC samples at 20 kW/m2
Figure 12: Transmission of heat through FFC sample at 10 kW/m2
Time (s)
Time (s)
Temperature (°C)Temperature (°C)
Exponent (Sample 1)
Exponent (Sample 1)
Sample 1
Exponent (Sample 2)
Exponent (Sample 2)
Sample 2
Exponent (Sample 3)
Exponent (Sample 3)
Sample 3
Exponent (Sample 4)
Exponent (Sample 4)
Sample 4
189
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Comparison of Thermal Performance of Firefi ghter Protective
Clothing at Diff erent Levels of Radiant Heat Flux Density
temperature on the other side adjacent to the calo-
rimeter, due to which the amount of heat was de-
layed and lower values of Qc (kW/m2) and %TF(Qo)
were noted by the calorimeter. As a result, re ght-
ers are able to endure the heat for a longer period of
time and perform their activities before acquiring
any harmful injuries.
At 20 kW/m2, the curve pattern of samples 4 and 1
was similar to that of the curves for 10 kW/m2.
However, this time, the curve of sample 3 was atter
as compared to the curve of sample 2 and both
curves were overlapping each other from the time
of 40–57 seconds. A erwards, the curve of sample 2
was slightly atter than the curve of sample3. It was
also noticed that in Table 4, at 20 kW/m2, the value
of Qc relatively increased for each sample as com-
pared to the value of Qc for 10 kW/m2 due to which
steeper curves were acquired indicating the rate of
temperature rise occurring at a faster rate.
4 Conclusion
e re ghters’s safety is in uenced by the protec-
tive performance of re ghter protective clothing.
If the thermal protective behaviour of FFC can suc-
ceed in enhancing the confrontation time of re-
ghters against radiant heat ux density, they will
be able to save more lives and assets. e research
showed that sample 4, which had a higher thickness
value and high percentage of meta-aramid in the
outer shell, displayed better thermal resistance and
insulation properties as compared to the rest of
samples.
e outer shell of sample 4 depicted a lower value of
air permeability and the combination of outer shell
+ thermal barrier of sample 4 exhibited lower ther-
mal conductivity values with respect to other sam-
ples. Furthermore, the time of exposure to the heat
plate at the constant temperature of 150 °C was
longer in the case of sample 4. All these results sug-
gest that sample 4 had slightly better thermal prop-
erties as compared to the rest of samples.
Sample 4 yielded lower values of Qc and %TF(Qo)
in comparison to all other samples. However, with
the increase in the level of incident ux density,
there was also enhancement in the values of Qc and
percentage transmission values for all samples.
A further study is required where thermal barriers
would be replaced with suitable insulating materials
to determine the thermal protective performance.
Additionally, the outer shell should be coated with
nano-metallic particles like silver, Al2O3 and TiO2 to
evaluate the thermal protective performance of FFC.
Acknowledgments
is project is funded by the Technical University of
Liberec, Department of Clothing Technology under
SGS-2018, project reference number 21246.
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