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Annals of Occupational Hygiene Advance Access originally published online on November 14, 2008
Annals of Occupational Hygiene 2009 53(1):63-68; doi:10.1093/annhyg/men074
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© The Author 2008. Published by Oxford University Press on behalf of the British Occupational Hygiene Society

Testing Cold Protection According to EN ISO 20344: Is There Any Professional Footwear that Does Not Pass?

Kalev Kuklane1,*, Satoru Ueno2, Shin-Ichi Sawada2 and Ingvar Holmér1

1 The Thermal Environment Laboratory, Division of Ergonomics and Aerosol Technology, Department of Design Sciences, Faculty of Engineering, Lund University, SE-22100 Lund, Sweden
2 International Center for Research Promotion and Informatics, Japanese National Institute of Occupational Safety and Health, 214-8585 Kawasaki, Japan

* Author to whom correspondence should be addressed. Tel: +46-46-222-7833; fax +46-46-222-4431; e-mail: kalev.kuklane{at}design.lth.se


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 FUNDING
 ACKNOWLEDGEMENTS
 REFERENCES
 
The present Comité Européen de Normalisation (CEN) and International Organization for Standardization (ISO) standards for safety, protective and occupational footwear EN ISO 20344–20347 classify footwear as cold protective by a pass/fail test where the limits are set for an allowed 10°C temperature drop inside the footwear during 30 min at a temperature gradient of ~40°C. It is questionable if a simple pass/fail test of this kind provides approved footwear that really protects the feet from cooling in exposures ranging from temperatures at +18°C to as low as or even lower than –50°C. This study selected for testing some professional footwear that could certainly not be considered as cold protective. Some footwear that could be used in cold was selected with as low insulation as the not cold-intended footwear. Also, a boot intended for cold was selected to be tested according to a modified standard at a temperature gradient of 70°C. The footwear selection was based on insulation measurements with a thermal foot model. All footwear did pass the test. Although it is clear for the user that a sandal, a mesh shoe or a thin textile shoe is not cold protective, it is not as clear that an item of safety footwear, that has as low insulation as those mentioned above, could be classified as cold protective according to the present standards. Because of this, the user might have a deceptive feeling of safety and may be exposed to higher risks. As practically all professional footwear may pass this cold test, then the method/requirements should be radically changed or such a test should be removed from the standards.

Keywords: cold-protective footwear • occupational safety • standard test method


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 FUNDING
 ACKNOWLEDGEMENTS
 REFERENCES
 
The temperature of the foot in dry conditions is determined by the balance between heat input from circulating blood and heat losses to the environment. Heat losses are three-dimensional and take place through sole, uppers and leg by conduction, radiation and convection and through openings by convection. The ability of footwear to affect this heat transfer is defined by its thermal insulation. This property can be measured on humans (Kuklane et al., 1999a) or on a thermal foot model (Kuklane and Holmér, 1998). The thermal insulation value allows a prediction of how well the footwear protects in different cold exposures (Kuklane, 2004).

The present European (CEN) and international (ISO) standards for safety, protective and occupational footwear EN ISO 20345–20347 (2004) classify footwear as cold protective by a pass/fail criterion. A 10°C temperature drop inside the footwear during 30 min at an initial suggested temperature gradient of ~40°C (EN ISO 20344, 2004) is allowed. The temperature change is measured with a sensor fixed onto the insole in the forepart of the footwear just above the point where the sole is in direct contact with the support platen. By this method, it is not possible to determine whether certain footwear that has passed the test will actually protect under certain cold conditions. A previous study (Kuklane et al., 1999b) expressed strong doubts whether a simple pass/fail test is correct for thermal testing. For example, the same footwear that helps to keep a good thermal comfort at –10°C when walking may be too cold for standing at the same temperature or walking at –25°C and too warm to be used at +10°C. It was also remarked that eventually any safety, protective or occupational footwear might pass the test. In that study, footwear for cool and cold conditions was studied. If the cold is defined just as a temperature below +18°C then all those footwear would certainly be cold protective.

During the past years, the standards have been reviewed; however, the test on cold protection has got only some cosmetic improvement, mainly directed towards making the testing procedure simpler and less time consuming. For example, the conditioning for 7 days was removed as well as the demand for specific conditioning humidity, and the temperature range was moved from +20 ± 2 to –20 ± 2 to +23 ± 2 to –17 ± 2°C for conditioning and testing, respectively. The same conditioning temperature applies also for heat transfer media consisting of 4 kg of 5 mm ball bearings that are poured into footwear before testing.

The aim of this paper is to demonstrate that the standard test method (EN ISO 20344, 2004) and the requirements (EN ISO 20345–20347, 2004) are neither relevant nor valid for testing and classification of cold-protective footwear.


   METHODS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 FUNDING
 ACKNOWLEDGEMENTS
 REFERENCES
 
The footwear was chosen from 19 types of professional footwear that were measured with a thermal foot model for and in cooperation with Japanese National Institute of Occupational Safety and Health. The thermal foot model test results were presented elsewhere (Ueno et al., 2008). The footwear was tested in order to provide thermal insulation values as a basis for recommendation of footwear for different thermal environments (Kuklane, 2004). It is generally recognized that the thermal foot method is the most relevant and valid method to measure thermal insulation of whole products. The method is similar to that used for whole clothing (EN 342, 2004; EN ISO 15831, 2004) and gloves/mittens (EN 511, 2006).

For this study, five types of footwear were selected that should not provide protection against cold due to their construction and low insulation value (Fig. 1, Table 1). Also, a cold-protective boot intended for cold (C) was included. With the exception of this one, none of the tested footwear had higher insulation than ordinary summer/indoor shoes according to thermal foot model tests.


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  		Table 1. Footwear from Cofra, Italy (C), and Midori Anzen, Japan (H, F, R, B and S), and the effective insulation values (Icle, m2 °C W–1), i.e. air layer insulation subtracted without considering clothing area factor (fcl), of all foot zones (toes, mid-sole, heel and dorsal foot) and the mid-sole only

 


Figure 1
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  		Fig. 1. Footwear.

 
Tests were carried out according to EN ISO 20344. The standard allows increasing the upper height with a collar if the uppers are not enough high to support the heat transfer media. This was done with ordinary printer paper for footwear R and S. For footwear S, the printer paper was also taped in front of other openings (Fig. 2).


Figure 2
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  		Fig. 2. Footwear S with openings covered.

 
The test procedure was the following. The temperature sensors were fixed in the footwear (Fig. 3) onto the insole, for measuring the temperature in the forepart of the footwear directly above the area where the sole contacts the support platen (Fig. 4), as specified by the section ‘5.13 Determination of the insulation against cold’ of the standard (EN ISO 20344, 2004). One of the sensors was a thermocouple fixed to a copper disc as specified by the standard. The data from this sensor was recorded with a logger Testo 177-T4 (accuracy ± 0.3°C). As this sensor showed a specific temperature increase (~0.5°C) after lifting the footwear into the cold chamber (Fig. 5), then an extra sensor was added. It was an external precision sensor connected to a modular signal recorder (MSR) 145W logger (accuracy ±0.1°C, Glattbrugg, Switzerland).


Figure 3
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  		Fig. 3. Placement of the sensors (footwear H).

 


Figure 4
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  		Fig. 4. Placement of the footwear (F) in a cold chamber with an arrow pointing to sensor location.

 


Figure 5
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  		Fig. 5. Temperature profiles in a test (boot B) with start criteria for recording of the 30-min temperature drop: (1) real start—footwear has been placed and the chamber closed, (2) the MSR sole sensor value drops <23°C and (3) the disc sensor (thermocouple) value drops <23°C. Initial temperature drop in MSR-ambient sensor depends on that it was moved together with footwear from warm to cold chamber.

 
The test pieces and heat transfer medium consisting of 4000 g of 5 mm diameter stainless steel balls were conditioned at 23.1 ± 0.0°C until the temperature of the insole stayed constant (allowed by standard 23 ± 2°C). Then the steel balls were poured into the footwear. The footwear stayed at the conditioning temperature for ~30 min more in order to assure the constant temperature values. The air velocity during conditioning was 0.36 ± 0.03 m s–1.

After the temperature of the outsole became constant at 23.1 ± 0.0°C, the test piece was placed into the cold chamber with an environmental temperature of –16.9 ± 0.1°C (allowed by standard –17 ± 2°C) on a support platen of copper for at least 40 min. During the modified tests with boot C, the temperature gradient was set to 70°C. This was achieved by keeping the conditioning temperature the same as in standard, i.e. +23°C, while the testing temperature was lowered to –47°C instead of standard's –17°C.

During the tests, the footwear collar was sealed with an insulating cover with an elongated hole that corresponded to the cover suggested by the standard (Fig. 4). The copper plate had the dimensions of 500 x 300 x 5 mm and in this way made the conditions more tough by adding more mass (thermal inertia) and contact area with cold air compared to standard plate (350 x 150 x 5 mm). In all cases, the air velocity in the test chamber at the ankle level stayed low at 0.15 ± 0.04 m s–1 (not specified in the standard).

The temperature decrease during whole exposure was recorded and temperature decrease within 30 min was calculated. If the temperature drop did not exceed 10°C (EN ISO 20345–20347, 2004) then footwear passed the test and could be classified as cold-protective footwear. The standard (EN ISO 20344, 2004) does not define exactly the start point of the recording; however, it may be understood that after sealing the insulating cover the measurements could be started. In order to make the test tougher and exclude the initial effect of footwear mass (thermal inertia) and consider only relatively linear cooling curve, an additional start criterion was defined at a point where insole temperature passed 23°C for determining the temperature drop in footwear within 30 min. The temperature drop was considered to decide pass or fail according to the standard.

The criteria for starting points are shown in Fig. 5. A ‘real start’ criterion starts when the footwear is placed in the test position and the chamber was closed. This period includes thermal changes related to the footwear thermal inertia and development of stable heat loss related to temperature gradient. The start time was checked after the experimenter had left the cold chamber and it applied for both sensors. The second start criterion was based on the last MSR sole sensor value which was >23°C. This period involved less initial cooling phase of the footwear. As the sensors behaved slightly differently, then the third start criterion was based on the last disc sensor value that was >23°C. This period was not in practice dependent on any of the initial cooling phase of the footwear. The initial temperature drop in MSR ambient sensor depended on the move together with footwear from warm to cold chamber. The mean ambient air temperature value (Table 2) was acquired based on the 10th to 30th minutes of each start criterion. During a pretest, the ambient sensor was placed in cold chamber during conditioning beforehand. The effect of entering the chamber to place the footwear raised the ambient air temperature values by <1°C for <2 min only, i.e. such a change could not affect the thermal mass of the support platen, and calculation of temperature change based on the start criteria 2 and 3 could not be affected by that change at all. Each item of footwear, except C, was tested twice (the standard requires testing two samples).


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  		Table 2. Conditioning and test temperatures, mean gradients and footwear ranked by temperature drop (°C) for each start criterion (see Fig. 5): (1) real start—footwear has been placed and the chamber closed (both sensors), (2) the last MSR sole sensor value is >23°C and (3) the last disc sensor (thermocouple) value is >23°C

 

   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 FUNDING
 ACKNOWLEDGEMENTS
 REFERENCES
 
The temperature decreases measured by EN ISO 20344 are ranked in Table 2. The calculation criteria for temperature drop ranked the footwear generally identically with just small differences, except for criterion 3 where initial mass related slower cooling was excluded. All footwear passed the test regardless of the start criterion. Thus, all tested footwear is approved and can be CE-marked (Comité Européen) as cold-protective footwear. As the test is a pass/fail test and does not indicate how well the footwear protects against cold, there is no recommendation to the user in what temperature they can be used. It should be remembered here that the thermal insulation values (Table 1) of the tested footwear, except for C, were similar to those of shoes for temperate weather.

Footwear C is intended for cold protection. Its insulation value (Icle, foot) was almost twice as high or higher than the other footwear. It also passed a modified standard test at a higher temperature gradient (70°C) with good margins (Table 2).

When looking at insulation values of the low-insulation footwear (Table 1), then F, H and R were very similar for both whole foot and sole insulation. B had a lower insulation for both foot and sole, and S had the lowest total foot insulation (S was measured on thermal foot model without paper covering the openings), while the sole insulation was the highest. As the temperature drop was measured at the sole and the openings of S were closed by paper, then this footwear managed the test very well compared to B, R and H. However, most probably it would have passed the test also if a thin sock or just mesh would have been used to keep the steel balls at place as the mesh shoe (R) did pass the test. On the other hand, if testing with wind, e.g. >0.40 m s–1, then both these shoes (R and S) might have failed. However, the EN ISO 20344 (2004) does not define air velocity during testing.

The test at lower temperature gradient that is still allowed by the standard according to conditioning (23 ± 2°C) and test conditions (–17 ± 2°C), e.g. the gradient of 37°C at 21.5 ± 0.5 and –15.5 ± 0.5°C for conditioning and testing, respectively (Kuklane et al., 1999b), would allow even less insulated footwear than used in this study to pass the test and be classified as cold-protective footwear.

Comparing temperature drop ranking (Table 2) with insulation values (Table 1), the values seem not to be correlated as they were in an earlier study (Kuklane et al., 1999b). Such a difference may be related to the fact that in the previous study all footwear were calf high boots with airtight outer layer and their insulation differed considerably. In this study, the footwear had a different grade of open structures in the footwear uppers and apparently different air permeability of footwear surface material but also relatively similar thermal insulation.

The main issue, however, is not that a sandal (S), a shoe with mesh uppers (R) or a thin textile shoe for clean rooms (H) did pass the test. With such footwear, it is clear for everybody that these are not for protection against cold. The problem is that the footwear (B and F) that has as low insulation as S, R and H may be classified as cold protective and in this way giving the user a deceptive safety feeling and exposing him/her to higher risks. Footwear F is in the catalogue classified as heat-protective footwear. As insulation is non-directional, then it protects both against cold and heat. It might be questionable if F actually does protect the user and raises a question if it was tested according to heat insulation test of the same standard (section 5.12, EN ISO 20344, 2004) that exploits the same test principles.

All tested low insulation footwear are more or less suitable for temperatures down to +10°C, but certainly not below –10°C. Even if it is possible to improve the standard method with extra ranking criteria, one is still not able to estimate without a major study how these ranks fit with the combination of: (i) ambient and ground temperature, (ii) different activity levels of the users and (iii) the use of different types of socks and insocks.

Big organizations may have a chance to test a few samples in the field before purchase of their equipment, but smaller enterprises would need to rely on standard testing and proper labelling. A field study in dairy farms (Kuklane et al., 2001) at ambient temperatures generally between 10 and 20°C showed that most of the farmers used rubber boots type B. The toe temperatures shifted ~20°C. In some cases, even the average toe temperature stayed <20°C and could reach even down to 13°C. Such a chronic cold exposure may cause various types of health trouble later in life.

The thermal insulation of the footwear is the most important property determining heat exchange in the cold. However, under certain conditions, the moisture handling properties of the footwear become important as well. Sweating may take place, in particular during higher activities. Very little moisture and vapour pass through the relatively thick material. Ventilation of the tight-fitting shoe via the leg opening takes place but is limited (Kuklane et al., 2000). Socks and soles may be used as moisture absorbers. The best solution to the problem, however, is to stay dry and this is much of a disciplinary and behavioural question. Proper routines to take care of the feet and footwear with information on the insulation value would give both military and industrial leaders what is required to choose and recommend the required protection level of footwear and the best combination of footwear–sock system for their subordinates.


   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
FUNDING
 ACKNOWLEDGEMENTS
 REFERENCES
 
All tested footwear passed the test, i.e. most professional footwear would pass the test. It is clear for the user that a sandal, a mesh shoe and a thin textile shoe are not cold protective. The problem is that the professional footwear, that has as low insulation as those mentioned above, may be classified as cold protective according to the present EN ISO 20344–20347 (2004). In this way, the user might be provided with a deceptive safety feeling and may be exposed to higher risks. The test results give no information to the wearer how well the footwear protects against cold. The present test is neither relevant nor valid. Testing the footwear according to this test is a waste of resources for both test houses and manufacturers. Therefore, the test method in its present form should be withdrawn and replaced with a more discriminating, relevant and valid method.


   FUNDING
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 FUNDING
ACKNOWLEDGEMENTS
 REFERENCES
 
Lund University; Japanese National Institute of Occupational Safety and Health.


   ACKNOWLEDGEMENTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 FUNDING
 ACKNOWLEDGEMENTS
REFERENCES
 
The authors thank Cofra, Italy, for allowing publishing the results of a special test.

Received March 14, 2008; in final form August 27, 2008


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 FUNDING
 ACKNOWLEDGEMENTS
 REFERENCES
 

EN 342. Protective clothing—ensembles and garments for protection against cold (2004) Brussels, Belgium: European Committee for Standardization.

EN 511. Protective gloves against cold (2006) Brussels, Belgium: European Committee for Standardization.

EN ISO 15831. Clothing—physiological effects—measurement of thermal insulation by means of a thermal manikin (2004) Brussels, Belgium: European Committee for Standardization.

EN ISO 20344. Personal protective equipment—test methods for footwear (2004) Brussels, Belgium: European Committee for Standardization.

EN ISO 20345. Personal protective equipment—safety footwear (2004) Brussels, Belgium: European Committee for Standardization.

EN ISO 20346. Personal protective equipment—protective footwear (2004) Brussels, Belgium: European Committee for Standardization.

EN ISO 20347. Personal protective equipment—occupational footwear (2004) Brussels, Belgium: European Committee for Standardization.

Kuklane K. The use of footwear insulation values measured on a thermal foot model. Int J Occup Saf Ergon (2004) 10:79–86.[Medline]

Kuklane K, Holmér I. Effect of sweating on insulation of footwear. Int J Occup Saf Ergon (1998) 4:123–36.[Medline]

Kuklane K, Afanasieva R, Burmistrova O, et al. Determination of heat loss from the feet and insulation of the footwear. Int J Occup Saf Ergon (1999a) 5:465–76.[Medline]

Kuklane K, Holmér I, Afanasieva R. A comparison of two methods of determining thermal properties of footwear. Int J Occup Saf Ergon (1999b) 5:477–84.[Medline]

Kuklane K, Holmér I, Giesbrecht G. One week sweating simulation test with a thermal foot model. In: 3IMM, the third international meeting on thermal manikin testing—Nilsson HO, Holmér I, eds. (2000) 106–13. Arbete och Hälsa 2000:4. Stockholm, Sweden: National Institute for Working Life.

Kuklane K, Gavhed D, Fredriksson K. A field study in dairy farms: thermal condition of feet. Int J Ind Ergon (2001) 27:367–73.

Ueno S, Kuklane K, Holmer I, et al. Thermal resistance of occupational footwear used in Japan (2008) Local Organizing Committee of the 18th International Congress on Biometeorology, 22–26 September 2008, Tokyo, Japan.


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