SIST-V CLC Guide 29:2009
Temperatures of hot surfaces likely to be touched -- Guidance document for Technical Committees and manufacturers
Temperatures of hot surfaces likely to be touched -- Guidance document for Technical Committees and manufacturers
This document provides guidance for assessing the risk of a burn from unintentional contact with readily accessible surfaces of electrical equipment under the scope of the Low Voltage Directive. This document establishes surface temperature limits, where such limits are required, and describes the maximum contact periods with a hot surface that a person may be subjected to without being exposed to a risk of burn. Curves of maximum temperatures versus contact times are described for different types of material with different types of surfaces. This document does not address temperature limits for hot functional surfaces. This document applies to surfaces of products likely to be touched by any person. The limit values may be taken into consideration by Technical Committees in determining surface temperature limits in product standards. Manufacturers may also use the limit values to assist in their risk assessment, if a product standard is not applied.
It is not within the scope of this document to set temperature limits for the following zones or surfaces:
- hot functional surfaces;
- adjacent surfaces;
- handles, control knobs including keypads, keyboards and the like;
- surfaces not likely to be touched.
Temperature vročih površin, kjer lahko pride do dotika - Vodila za tehnične odbore in proizvajalce
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-V CLC Guide 29:2009
01-februar-2009
7HPSHUDWXUHYURþLKSRYUãLQNMHUODKNRSULGHGRGRWLND9RGLOD]DWHKQLþQHRGERUH
LQSURL]YDMDOFH
Temperatures of hot surfaces likely to be touched -- Guidance document for Technical
Committees and manufacturers
Ta slovenski standard je istoveten z: CLC Guide 29:2007
ICS:
01.120 Standardizacija. Splošna Standardization. General
pravila rules
13.180 Ergonomija Ergonomics
SIST-V CLC Guide 29:2009 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST-V CLC Guide 29:2009
---------------------- Page: 2 ----------------------
SIST-V CLC Guide 29:2009
CENELEC Guide 29
Temperatures of hot surfaces
likely to be touched
Guidance document for
Technical Committees and manufacturers
The present Guide has been developed in response to EC Standardisation Mandate M/346 in the field of the
Low Voltage Directive 2006/95/EC addressing surface temperatures of accessible non-functional surfaces.
The CENELEC Technical Board approved this Guide in April 2007.
Edition 1 / April 2007
---------------------- Page: 3 ----------------------
SIST-V CLC Guide 29:2009
Rue de Stassartstraat, 35
B - 1050 Brussels
Tel.: + 32 2 519 68 71
Fax: + 32 2 519 69 19
www.cenelec.org
---------------------- Page: 4 ----------------------
SIST-V CLC Guide 29:2009
Temperatures of hot surfaces likely to be touched CENELEC Guide 29
Foreword
This Guide was prepared by CENELEC BTTF 120-1, Surface temperatures.
The text of the draft was submitted to the vote and was approved by the CENELEC Technical Board
as CENELEC Guide 29 on 2007-04-11.
This guidance document for Technical Committees and manufacturers has been developed in
response to EC Standardisation Mandate M/346 in the field of the Low Voltage Directive 2006/95/EC
addressing surface temperatures of accessible non-functional surfaces.
Edition 1 / April 2007 3
---------------------- Page: 5 ----------------------
SIST-V CLC Guide 29:2009
CENELEC Guide 29 Temperatures of hot surfaces likely to be touched
Contents
Page
1 Scope. 6
2 Normative references . 6
3 Definitions . 6
3.1 surface temperature (Ts). 6
3.2 contact period (t). 6
3.3 thermal inertia . 7
3.4 material properties of the surface. 7
3.5 burn threshold. 7
3.6 hot functional surface.7
3.7 adjacent surface . 7
3.8 handles or control knobs including keypads, keyboards and the like. 7
3.9 touchable surfaces.7
3.10 arms reach. 8
3.11 skin temperature (T ). 9
C
4 Assessment of the risk of burning . 9
4.1 Procedure . 9
4.2 Identification of surfaces . 9
4.3 Task analysis . 10
4.4 Measurement of the surface temperatures. 10
4.5 Choice of applicable burn threshold . 10
4.6 Comparison between surface temperature and burn threshold . 11
4.7 Result of the risk assessment . 11
5 Application of protective measures. 11
5.1 Touchable surfaces. 11
5.2 Adjacent surfaces . 12
6 Burn thresholds . 12
6.1 Determination of the contact period. 12
6.2 Selection of the burn threshold. 13
6.3 Texture of the surface . 14
7 Documentation. 14
Annex A Burn thresholds . 15
A.1 General. 15
A.2 Burn threshold data. 16
4 Edition 1 / April 2007
---------------------- Page: 6 ----------------------
SIST-V CLC Guide 29:2009
Temperatures of hot surfaces likely to be touched CENELEC Guide 29
Annex B (informative) Scientific background. 21
Annex C (informative) Thermal properties of selected materials. 23
Annex D (informative) Examples for protective measures against burns. 24
D.1 Protective measures against burns (general) . 24
D.2 Example for protective measures. 24
Bibliography . 26
Figures
Figure 1 – Definition of the different touchable parts of an equipment. 8
Figure 2 – Arms reach - the distance is interpreted as either a fully stretched person (a) or a
person reaching for an item (b). Worst case of either (a) or (b) to be used. . 8
Figure A.1 – Illustration of relationship between the burn threshold and contact period when a
hot surface is touched by the skin. 17
Figure A.2 – Burn threshold spread when the skin is in contact with a hot smooth surface
made of bare (uncoated) metal. 17
Figure A.3a – Rise in the burn threshold spread from Figure A2 for metals which are coated by
lac of a thickness of 50 µm, 100 µm and 150 µm. 18
Figure A.3b – Rise in the burn threshold spread from Figure A2 for metals which are coated by
porcelain enamel (160 µm) / powder (60 µm), powder (90 µm) and polyamide 11 or 12
(thickness 400 µm) . 18
Figure A.4 – Burn threshold spread when the skin is in contact with a hot smooth surface
made of ceramics, glass and stone materials . 19
Figure A.5 – Burn threshold spread when the skin is in contact with a hot smooth surface
made of plastics . 19
Figure A.6 – Burn threshold spread when the skin is in contact with a hot smooth surface
made of wood. 20
Tables
Table 1 – Arms reach . 8
Table 2 – Contact period . 12
Table A.1 – Burn threshold for longer contact times . 20
Table C.1 – Thermal properties of selected materials (taken from [3]). 23
Edition 1 / April 2007 5
---------------------- Page: 7 ----------------------
SIST-V CLC Guide 29:2009
CENELEC Guide 29 Temperatures of hot surfaces likely to be touched
1 Scope
This document provides guidance for assessing the risk of a burn from unintentional contact with
readily accessible surfaces of electrical equipment under the scope of the Low Voltage Directive.
This document establishes surface temperature limits, where such limits are required, and describes
the maximum contact periods with a hot surface that a person may be subjected to without being
exposed to a risk of burn. Curves of maximum temperatures versus contact times are described for
different types of material with different types of surfaces.
This document does not address temperature limits for hot functional surfaces.
This document applies to surfaces of products likely to be touched by any person.
The limit values may be taken into consideration by Technical Committees in determining surface
temperature limits in product standards. Manufacturers may also use the limit values to assist in their
risk assessment, if a product standard is not applied.
It is not within the scope of this document to set temperature limits for the following zones or surfaces:
- hot functional surfaces;
- adjacent surfaces;
- handles, control knobs including keypads, keyboards and the like;
- surfaces not likely to be touched.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN ISO 13732-1:2006, Ergonomics of the thermal environment – Methods for the assessment of
human responses to contact with surfaces – Part 1: Hot surfaces
EN 61032:1998, Protection of persons and equipment by enclosures - Probes for verification
3 Definitions
For the purpose of this guide, the following definitions apply:
3.1
surface temperature (Ts)
temperature of a surface, measured in degrees Celsius, at an ambient temperature of 25°C -5°C/+0°C
3.2
contact period (t)
time during which contact with the surface occurs
NOTE In Figures A.2 to A.6 contact duration (D) is used to determine the contact period (t)
6 Edition 1 / April 2007
---------------------- Page: 8 ----------------------
SIST-V CLC Guide 29:2009
Temperatures of hot surfaces likely to be touched CENELEC Guide 29
3.3
thermal inertia
product of the density, thermal conductivity and specific thermal capacity of material
3.4
material properties of the surface
chemical/physical composition of the material and the characteristics (rough, smooth) of the surface
3.5
burn threshold
surface temperature defining the boundary between no burn and a superficial partial thickness burn,
caused by contact of the skin with a hot surface for a specified contact period
3.6
hot functional surface
surface which is intentionally heated by an internal heat source and which has to be hot to carry out
the function for which the equipment is intended to be used. For example, the soleplate of an iron, or
curling tongs.
Some equipment have hot surfaces as a consequence of how they generate their output, for example
lamps within a luminaire, and are considered in terms of their treatment as equivalent to a hot
functional surface
3.7
adjacent surface
a surface adjacent to a functional surface.
The adjacent surface and the functional surface normally consist of the same piece of material or are
in direct thermal contact and have similar thermal properties. The adjacent surface is not heated
intentionally during use of the product. However, as it is adjacent to the functional surface and may
become hot through conduction, its temperature will be in the range between the functional and a
touchable surface
3.8
handles or control knobs including keypads, keyboards and the like
part of the equipment that a user needs to touch to operate or adjust the equipment
3.9
touchable surfaces
all other surfaces that are likely to be touched when the equipment is operated during normal use and
foreseeable misuse. The equipment has to be installed according to the manufacturer’s instructions.
NOTE This means an oven intended for build in should be installed according to the manufacturer’s instructions before
identification of the touchable surfaces
Edition 1 / April 2007 7
---------------------- Page: 9 ----------------------
SIST-V CLC Guide 29:2009
CENELEC Guide 29 Temperatures of hot surfaces likely to be touched
Touchable surface: Surface which may be touched
Handles or
Adjacent surface
control knobs
including
Hot FUNCTIONAL
keyboards
surface
and the like
Figure 1 – Definition of the different touchable parts of an equipment
3.10
arms reach
the distance measured from the floor to the fingertips of a person. As shown in Figure 2, it has to be
taken into account that a person can reach not only in a vertical direction as shown in Figure 2 (a), but
also in a circle defined approximately in Figure 2 (b).
1/3
1/1
2/3
(a)
(b)
Figure 2 – Arms reach - the distance is interpreted as either a fully stretched person (a)
or a person reaching for an item (b). Worst case of either (a) or (b) to be used
Table 1 gives guidance on arms reach for different age groups.
Table 1 – Arms reach
Age Arms reach [see Figure 2(a)],
calculated from the floor
years metre
Children less than 2 years 1,00
Children from 2 years to less than 6 years 1,50
Children from 6 years to less than 14 years 1,80
Adult 2,30
NOTE The values in Table 1 are average values
8 Edition 1 / April 2007
---------------------- Page: 10 ----------------------
SIST-V CLC Guide 29:2009
Temperatures of hot surfaces likely to be touched CENELEC Guide 29
3.11
skin temperature (T )
C
temperature at a depth of 80 µm below the surface of the skin, measured in degrees Celsius
4 Assessment of the risk of burning
Normally it is sufficient to follow the product standard. The manufacturer only needs to carry out a risk
assessment, if the product standard does not take account of the foreseeable use in relation to the
temperatures of surfaces likely to be touched, or if no relevant product standard exists.
4.1 Procedure
The different types of surfaces or zones shall be identified according to 4.2.
To assess the risk of a cutaneous burn from surfaces likely to be touched, the steps described in 4.3
to 4.7 shall be carried out for surfaces identified in 4.2.4.
4.2 Identification of surfaces
All necessary information concerning the surfaces of a product shall be gathered to classify the
surfaces according to 4.2.1 to 4.2.4.
4.2.1 Identification of hot functional surfaces
Hot functional surfaces shall be identified when the equipment is installed as for normal use. See 3.6.
4.2.2 Identification of adjacent surfaces
Adjacent surfaces to hot functional surfaces shall be identified. See 3.7.
4.2.3 Identification of handles or control knobs including keypads, keyboards and the like
Relevant parts shall be identified. See 3.8.
4.2.4 Identification of non-functional touchable surfaces
All necessary information concerning the touchable surfaces of the equipment, including the following,
shall be gathered:
- accessibility of the surfaces, see 4.2.4.1;
- approximate estimation of surface temperatures (hot, moderate, cold);
- material and texture of the surfaces;
- all normal operating conditions of the equipment including the worst case, i.e the setting which
results in maximum temperatures of the surfaces;
- the probability of contact.
4.2.4.1 Touchable surfaces
A surface is considered touchable if parts of the appropriate test probe (EN 61032) can touch the
surface. It is the responsibility of the technical committees to decide which test probe shall be used.
If the equipment is installed out of reach it is not considered touchable.
Edition 1 / April 2007 9
---------------------- Page: 11 ----------------------
SIST-V CLC Guide 29:2009
CENELEC Guide 29 Temperatures of hot surfaces likely to be touched
It is up to the manufacturers’ risk assessment, based upon the relevant product standard(s), to define
the foreseeable use.
NOTE “relevant product standard(s)” means, that the standard(s) covers all risks of the equipment in question.
4.3 Task analysis
All necessary information concerning the use of the product shall be collected. By means of analysis
or observation, the activities and tasks involved in using the product shall be described. Attention shall
be paid to the means of possible contact with hot surfaces and to which persons (users of the product
and others) the contact may happen. From the task analysis the following information is obtained:
- surfaces which may be touched unintentionally,
- users or other persons who will likely touch or may touch the surfaces unintentionally,
- range of operation of the product,
- probability of touching,
- statistical data on relevant incidents, if available,
- maximum setting of the temperature of the product.
4.4 Measurement of the surface temperatures
The surface temperatures shall be measured on touchable surfaces.
The measurement shall be carried out under normal operating conditions of the product that will result
in the maximum surface temperature. The chosen operating conditions should reflect the
manufacturer’s intended use of the product while excluding deliberate misuse or unauthorised
modifications of the product or its operating parameters by the user.
If a technical committee has a specified temperature measurement method, that method shall be
used. Otherwise the measurement of the surface temperature shall be carried out by means of an
electrical thermometer with a contact sensor made of metal and insignificant heat capacity. The
accuracy of the instrument shall be at least ± 1 °C in the range up to 50 °C and at least ± 2 °C in the
range above 50 °C.
NOTE The data in Annex A is based on measurement methods described in EN ISO 13732-1:2006.
4.5 Choice of applicable burn threshold
Based on the identification of the hot surfaces in 4.2, and from the task analysis in 4.3, and by taking
account of the surface material and texture, the applicable burn threshold may be chosen using the
data in Annex A, if available.
NOTE 1 Annex A provides data and curves for some surface material and texture combinations. Further study may be
necessary to determine burn thresholds for materials and/or textures not covered in Annex A.
The contact period to be used for selecting the burn threshold must be according to Clause 6, and
must take into consideration the different groups of persons that are likely to come into contact with
the surface.
NOTE 2 For products that can be expected to be operated only under supervision or if there is a lower risk of exposure to
children and/or people with physical disabilities, applicable contact periods may be reduced.
10 Edition 1 / April 2007
---------------------- Page: 12 ----------------------
SIST-V CLC Guide 29:2009
Temperatures of hot surfaces likely to be touched CENELEC Guide 29
4.6 Comparison between surface temperature and burn threshold
Compare the measured surface temperatures with the applicable burn thresholds:
- If the surface temperature is above the burn threshold, cutaneous injury upon contact with the hot
surface is to be expected.
- If the temperature lies below the burn threshold, the skin will not normally suffer injury.
- If the measured surface temperature lies inside the burn threshold spreads of the figures in
Annex A, cutaneous injury may or may not occur. This corresponds to the remaining uncertainty of
the burn threshold specification.
NOTE 1 The burn thresholds in EN ISO 13732-1:2006 relate to surface temperatures and not skin temperatures. The
relationship between surface temperatures and resultant skin temperatures is discussed in A.1. The occurrence of a burn based
on skin temperature is discussed in Annex B.
NOTE 2 In some technical committees (e.g. TC 108), it is under consideration to measure a resultant surface temperature
after contact with the body has been established.
4.7 Result of the risk assessment
Based on the analysis in 4.3, the probability of touching a part of the surface of the product which has
a temperature higher than the burn threshold shall be determined. As a result, the risk of burning is
determined in terms of
- exceeding or falling short of the burn threshold for all parts of the touchable surface of the product,
- probability of contact.
NOTE Hints for the risk assessment are given in Subclause 6.3 of EN ISO 13732-1:2006.
5 Application of protective measures
Protective measures shall be considered according to 5.1 and 5.2. Afterwards the process of risk
assessment shall be repeated until the risk level is acceptable.
5.1 Touchable surfaces
If the risk assessment shows that there is a risk of burning it shall be decided whether protective
measures are necessary and, if so, which protective measures are appropriate. In order to reduce or
to eliminate any risk of burning, protective measures may be applied to products and may also be
specified in standards for products which are to be produced in the future.
In general, engineering, organisational or personal protective measures may be applied. Whether it is
necessary to apply protective measures at all and which specific measures are appropriate will
depend on the context in which a product will be used.
It is outside of the scope of this document to specify protective measures. It is the task of
manufacturers and also of standardisation groups to decide upon protective measures appropriate to
the intended use of a product. Protective means should be provided together with the equipment.
One of several possible protective measures is the limitation of the surface temperature below the
burn threshold. To achieve this, surface temperature limit values may be established at or below the
burn threshold in the product standard. It is then the task of the manufacturer of the product to apply
technical solutions in order to comply with the established limit values.
Limitation of surface temperatures and establishment of limit values is applicable only for those parts
of a product which are not deliberately heated as an integral part of the functioning of the product.
Edition 1 / April 2007 11
---------------------- Page: 13 ----------------------
SIST-V CLC Guide 29:2009
CENELEC Guide 29 Temperatures of hot surfaces likely to be touched
5.2 Adjacent surfaces
As the temperature of an adjacent surface may be in excess of the limits of the touchable surfaces,
protective measures shall be considered to minimize the risk of burning.
Examples of applicable protective measures in this case include limiting the dimensions to the
smallest possible area, use of alternative materials or surface structures to limit the likelihood of
touching of adjacent surface, reduction of the temperature flow by de-coupling or insulation from the
functional surface.
It is the responsibility of the technical committee or manufacturer to define the size, the temperature
limits and any other relevant aspects of this surface, where necessary.
6 Burn thresholds
6.1 Determination of the contact period
6.1.1 General
For the selection of appropriate contact periods, a minimum contact period of 0,5 s – 1 s shall be
used. If extended reaction time is to be expected (e.g. for people who need special precautions), a
longer contact period of up to 15 s should be selected. See Table 2.
It is essential that when selecting the contact periods, a distinction is made based upon those who
may come into contact with the hot surface. See Table 1, Table 2 and 6.1.2:
- adults,
- children,
- elderly people,
- people with physical disabilities.
Table 2 – Contact period
Group Contact period in
seconds
Adults 0,5-1
Children less than 2 years 15
Children from 2 years to less than 6 years 4
Children from 6 years to less than 14 years 2
Elderly people 1-4
Physical disabilities According to nature of
disability
NOTE The exact value for adults shall be chosen based on the nature of the products and where they are intended to be used.
6.1.2 Selection of contact periods
6.1.2.1 Adults
For adults a minimum contact period of 0,5 s - 1 s shall be used.
12 Edition 1 / April 2007
---------------------- Page: 14 ----------------------
SIST-V CLC Guide 29:2009
Temperatures of hot surfaces likely to be touched CENELEC Guide 29
6.1.2.2 Children
If children may touch the touchable surfaces, an extended reaction time due to their age is to be
expected, and at least 4 s shall be selected.
If children aged between 6 and 14 may touch a touchable surface, a contact period of 2 s may be
used.
Until 24 months of age, children do not have reflexes fast enough to respond to contact with a hot
surface. Thus, the contact period may be up to 15 s for very young children.
6.1.2.3 Elderly people
If elderly people may touch the touchable surface, 1 s shall be selected as the minimum contact
period. If an extended reaction time due to their age is to be expected, at least 4 s shall be selected.
NOTE The majority of products covered by the Low Voltage Directive are commonly used by elderly people.
6.1.2.4 People with physical disabilities
Where people with physical disabilities may come in contact with hot surfaces, 1 s shall be selected as
the minimum contact period. Special consideration shall be made by the technical committee taking
into account the nature of the disabilities and the use of the product.
6.2 Selection of the burn threshold
With the aid of the established contact period, the burn threshold shall be determined from the graphs
in the figures in Annex A or from Table A.1.
For contact periods between 10 s and 1 min, an interpolation can be made between the burn threshold
value indicated for the specific material in the figures in Annex A for 10 s and the value in Table A.1
corresponding to the contact period of 1 min.
For contact periods longer than 1 min, lying between the time periods specified in Table A.1, it is
convenient to interpolate between the burn threshold values set for the next shorter and for the next
longer contact period. Figures for thresholds to be adapted for 0,5 s to 15 s (see A.2).
For the purpose of setting temperature limit values, it is recommended to proceed in the following way:
inside the spread of burn threshold values for material group in the figures in Annex A it is
recommended to choose a temperature value lying nearer the lower end of the spread if the
probability of touching the hot surface is high, and to choose a temperature value nearer the higher
end of the spread when the probability of touching the surface is less.
Materials not expressly mentioned in the figures in Annex A and Table A.1 can in some cases be
evaluated according to their heat conductivity properties. The thermal inertia (see Annex B and
Annex C) of the respective material has to be compared to the thermal inertia of the following groups
of materials: metals, ceramics and glass materials, plastics or wood. The material can then be
accorded a burn threshold value from the material group with the same thermal inertia. The
prerequisite for th
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.