IEC GUIDE 117:2010

Electrotechnical equipment - Temperatures of touchable hot surfaces

IEC Guide 117:2010(E) provides guidance for assessing the risk, to any person, of a burn from contact with hot touchable surfaces of electrotechnical equipment. Establishes surface temperature limits, where such limits are required, and describes the maximum contact periods with a hot surface that any 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. These temperature limit values shall be taken into consideration by technical committees in determining surface temperature limits in product standards.

General Information

• Status: Published
• Publication Date: 12-Oct-2010
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.020 - Electrical engineering in general
• Technical Committee: ACOS - ACOS
• Current Stage: PPUB - Publication issued
• Start Date: 15-Oct-2010
• Completion Date: 13-Oct-2010

Standards Content (Sample)

IEC GUIDE 117 ®
Edition 1.0 2010-10
GUIDE
Electrotechnical equipment – Temperatures of touchable hot surfaces

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IEC GUIDE 117 ®
Edition 1.0 2010-10
GUIDE
Electrotechnical equipment – Temperatures of touchable hot surfaces

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
U
ICS 29.020 ISBN 978-2-88912-219-6
– 2 – Guide 117 © IEC:2010(E)
CONTENTS
FOREWORD.4
INTRODUCTION.5
1 Scope.6
2 Normative references .6
3 Terms and definitions .7
4 Assessment of the risk of burning.8
4.1 Procedure .8
4.2 Identification of surfaces .8
4.2.1 Identification of hot functional surfaces.8
4.2.2 Identification of adjacent surfaces .8
4.2.3 Identification of handles or control knobs including keypads,
keyboards and the like.9
4.2.4 Identification of touchable 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.10
4.7 Result of the risk assessment.11
5 Application of protective measures .11
5.1 Touchable surfaces .11
5.2 Adjacent surfaces.11
6 Burn thresholds .12
6.1 Determination of the contact period .12
6.1.1 General .12
6.1.2 Selection of contact periods.12
6.2 Selection of the burn threshold.13
6.3 Texture of the surface .13
7 Documentation .14
Annex A (normative) Burn thresholds.15
Annex B (informative) Scientific background .24
Annex C (informative) Thermal properties of selected materials.26
Annex D (informative) Examples for protective measures against burns.27
Bibliography.29

Figure 1 – Identification of the touchable parts of equipment (cross-hatched area) .8
Figure 2 – Arm’s reach – the distance is interpreted as either a fully stretched person
(a) or a person reaching for an item (b).9
Figure A.1 – Material temperature and contact period .17
Figure A.2 – Burn threshold spread when the skin is in contact with a hot smooth
surface made of bare (uncoated) metal.18
Figure A.3a – Rise in the burn threshold spread from Figure A.2 for metals that are
coated by shellac varnish of a thickness of 50 μm, 100 μm and 150 μm.19
Figure A.3b – Rise in the burn threshold spread from Figure A.2 for metals coated with
the specified materials .20

Guide 117 © IEC:2010(E) – 3 –
Figure A.4 – Burn threshold spread when the skin is in contact with a hot smooth
surface made of ceramics, glass and stone materials .21
Figure A.5 – Burn threshold spread when the skin is in contact with a hot smooth
surface made of plastics .22
Figure A.6 – Burn threshold spread when the skin is in contact with a hot smooth
surface made of wood.23

Table 1 – Arm’s reach.9
Table 2 – Contact period.12
Table A.1 – Burn threshold for longer contact times.23
Table C.1 – Thermal properties of selected materials (taken from [2]).26

– 4 – Guide 117 © IEC:2010(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROTECHNICAL EQUIPMENT –
TEMPERATURES OF TOUCHABLE HOT SURFACES

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This first edition of IEC Guide 117 has been prepared in accordance with ISO/IEC Directives,
Part 1, Annex A, by the IEC Advisory Committee on Safety (ACOS). This is a non-mandatory
guide in accordance with SMB Decision 136/8.
This Guide is based on CENELEC Guide 29.
The text of this IEC Guide is based on the following documents:
Four months’ vote Report on voting
C/1619/DV C/1636/RV
Full information on the voting for the approval of this Guide can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

Guide 117 © IEC:2010(E) – 5 –
INTRODUCTION
This Guide was initially prepared by CENELEC BTTF 120-1, Surface temperatures, and was
approved by the CENELEC Technical Board as CENELEC Guide 29.
The CENELEC guide has been modified to take into account IEC document preparation
procedures and those comments received from National Committees and Technical
Committees.
– 6 – Guide 117 © IEC:2010(E)
ELECTROTECHNICAL EQUIPMENT –
TEMPERATURES OF TOUCHABLE HOT SURFACES

1 Scope
This IEC Guide provides guidance for assessing the risk, to any person, of a burn from
contact with hot touchable surfaces of electrotechnical equipment. This Guide establishes
surface temperature limits, where such limits are required, and describes the maximum
contact periods with a hot surface that any 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.
These temperature limit values shall be taken into consideration by technical committees in
determining surface temperature limits in product standards. In making this determination,
consideration should be given to:
– the likelihood of contact with the heated part;
– the size and thermal capacity of the heated part;
– the expertise of the persons and their knowledge and experience relative to the
temperatures likely to be encountered in operating or servicing the product;
– the provision of adequate cautions or warnings; and
– other similar factors taking into account the task analysis specified in 4.3.
It is ultimately the responsibility of the technical committee to establish the acceptable
temperature limits (which may be higher) that may apply to touchable surfaces of products
under thei
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