CLC Guide 29:2007

SLOVENSKI STANDARD
01-februar-2009
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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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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
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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.

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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

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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

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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)

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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

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