IEC TR 62368-2:2025

IEC TR 62368-2 ®
Edition 4.0 2025-07
TECHNICAL
REPORT
Audio/video, information and communication technology equipment -
Part 2: Explanatory information related to IEC 62368-1:2023
ICS 33.160.01  ISBN 978-2-8327-0533-9

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CONTENTS
FOREWORD . 8
INTRODUCTION . 11
0 Principles of this product safety standard . 12
1 Scope . 15
2 Normative references . 15
3 Terms, definitions and abbreviations . 15
4 General requirements . 18
4.2 Energy source classifications . 20
4.6 Fixing of conductors and conductive parts . 24
4.7 Equipment for direct insertion into mains socket-outlets . 25
4.8 Equipment containing coin or button cell batteries . 25
4.9 Likelihood of fire or shock due to entry of conductive objects . 26
5 Electrically-caused injury . 26
5.4 Insulation materials and requirements . 42
5.5 Components as safeguards . 68
5.6 Protective conductor . 71
5.7 Prospective touch voltage, touch current and protective conductor current . 73
5.8 Backfeed safeguard in battery backed up supplies . 78
6 Electrically-caused fire . 80
6.2 Classification of power sources and potential ignition sources . 80
6.3 Safeguards against fire under normal operating conditions and abnormal
operating conditions . 84
6.4 Safeguards against fire under single fault conditions . 90
6.6 Safeguards against fire due to the connection of additional equipment . 115
7 Injury caused by hazardous substances . 115
8 Mechanically-caused injury . 119
8.1 General . 119
8.2 Mechanical energy source classifications . 119
8.3 Safeguards against mechanical energy sources . 120
8.4 Safeguards against parts with sharp edges and corners . 121
8.5 Safeguards against moving parts . 121
8.6 Stability of equipment . 122
8.7 Equipment mounted to a wall, ceiling or other structure . 123
8.8 Handle strength . 124
8.9 Wheels or casters attachment requirements . 124
8.10 Carts, stands, and similar carriers . 124
8.11 Mounting means for slide-rail mounted equipment (SRME) . 125
9 Thermal burn injury . 126
9.1 General . 126
9.2 Thermal energy source classifications. 130
9.3 Touch temperature limits. 131
9.4 Safeguards against thermal energy sources . 135
9.6 Requirements for wireless power transmitters . 136
10 Radiation . 137
10.2 Radiation energy source classifications . 137
10.3 Safeguards against laser radiation . 140
10.4 Safeguards against optical radiation from lamps and lamp systems
(including LED types) . 140
10.5 Safeguards against X-radiation . 140
10.6 Safeguards against acoustic energy sources . 140
Annex A Examples of equipment within the scope of IEC 62368-1 . 144
Annex B Normal operating condition tests, abnormal operating condition tests
and single fault condition tests . 144
B.1 General – Equipment safeguards during various operating conditions . 144
B.2 – B.3 – B.4 Operating modes . 148
Annex C UV radiation . 149
Annex D Test generators . 149
Annex E Test conditions for equipment intended to amplify audio signals . 149
Annex F Equipment markings, instructions, and instructional safeguards . 150
F.3 Equipment markings . 150
F.4 Instructions . 156
F.5 Instructional safeguards . 156
Annex G Components . 157
G.1 Switches . 157
G.7 Mains power supply cords and interconnection cables . 161
G.8 Varistors . 161
G.9 Integrated circuit (IC) current limiters . 162
G.11 Capacitors and RC units . 163
G.13 Printed boards . 167
G.14 Coatings on component terminals . 167
G.15 Pressurized liquid filled components or LFC assemblies . 167
Annex H Criteria for telephone ringing signals . 174
H.2 Method A . 174
H.3 Method B . 176
Annex J Insulated winding wires for use without interleaved insulation . 176
Annex K Safety interlocks . 176
K.7.1 Safety interlocks . 176
Annex L Disconnect devices . 177
Annex M Equipment containing batteries and their protection circuits . 178
M.1 General requirements . 178
M.2 Safety of batteries and their cells . 178
M.3 Protection circuits for batteries provided within the equipment . 186
M.4 Additional safeguards for equipment containing a secondary lithium battery . 186
Annex O Measurement of creepage distances and clearances . 189
Annex P Safeguards against conductive objects . 190
P.1 General . 190
P.2 Safeguards against entry or consequences of entry of a foreign object . 190
P.3 Safeguards against spillage of internal liquids . 191
P.4 Metallized coatings and adhesives securing parts . 192
Annex Q Circuits intended for interconnection with building wiring . 192
Q.2 Test for external circuits – paired conductor cable . 192
Annex R Limited short-circuit test . 193
Annex S Tests for resistance to heat and fire . 193
S.1 Flammability test for fire enclosure and fire barrier materials of equipment
where the steady-state power does not exceed 4 000 W . 193
S.2 Flammability test for fire enclosure and fire barrier integrity . 193
S.3 Flammability tests for the bottom of a fire enclosure . 194
S.4 Flammability classification of materials . 194
S.5 Flammability test for fire enclosure materials of equipment with a steady
state power exceeding 4 000 W . 194
S.6 Grille covering material, cloth, and reticulated foam . 195
Annex T Mechanical strength tests . 195
T.2 Steady force test, 10 N . 195
T.3 Steady force test, 30 N . 195
T.4 Steady force test, 100 N . 195
T.5 Steady force test, 250 N . 195
T.6 Enclosure impact test. 195
T.7 Drop test . 196
T.8 Stress relief test . 196
T.9 Glass impact test . 196
T.10 Glass fragmentation test . 196
Annex U Mechanical strength of CRTs and protection against the effects of
implosion . 196
U.2 Test method and compliance criteria for non-intrinsically protected CRTs . 196
Annex V Determination of accessible parts . 197
Annex X Alternative method for determining clearances for insulation in circuits
connected to an AC mains not exceeding 420 V peak (300 V RMS) . 197
Annex Y Construction requirements for outdoor enclosures. 198
Y.3 Resistance to corrosion . 199
Annex A (informative) Background information related to the use of surge suppressors . 200
A.1 Industry demand for incorporating surge suppressors in the equipment . 200
A.2 Considerations on surge suppressors bridging both sides of a safeguard . 202
A.3 Considerations on a surge suppresser used for ID1 external circuit in class II
equipment . 203
A.4 Information about follow current (or follow-on current) . 209
Annex B (informative) Background information related to measurement of discharges
– Determining the R-C discharge time constant for X and Y capacitors . 215
B.1 General . 215
B.2 EMC filters . 215
B.3 The safety issue and solution . 215
B.4 The requirement . 216
B.5 100 MΩ probes . 216
B.6 The R-C time constant and its parameters . 217
B.7 Time constant measurement. . 220
B.8 Effect of probe resistance . 223
B.9 Effect of probe capacitance . 224
B.10 Determining the time constant . 224
B.11 Conclusion . 226
Annex C (informative) Background information related to resistance to candle flame
ignition . 227
Annex D (informative) Surge suppressers used between mains and an external circuit
ID1 as specified in Table 13 . 228
Bibliography . 229

Figure 1 – Risk reduction as given in ISO/IEC Guide 51 . 13
Figure 2 – HBSE Process Chart . 14
Figure 3 – Protective bonding conductor as part of a safeguard . 17
Figure 4 – Safeguards for protecting an ordinary person . 21
Figure 5 – Safeguards for protecting an instructed person . 22
Figure 6 – Safeguards for protecting a skilled person . 22
Figure 7 – Flow chart showing the intent of the glass requirements . 24
Figure 8 – Conventional time/current zones of effects of AC currents (15 Hz to 100 Hz)
on persons for a current path corresponding to left hand to feet (see IEC 60479-
1:2018, Figure 20) . 29
Figure 9 – Conventional time/current zones of effects of DC currents on persons for a
longitudinal upward current path (see IEC 60479-1:2018, Figure 22) . 30
Figure 10 – Illustration that limits depend on both voltage and current . 31
Figure 11 – Typical example . 38
Figure 12 – Example 1 . 39
Figure 13 – Example 2 . 39
Figure 14 – Flow chart for determining clearances . 45
Figure 15 – Illustration of working voltage . 46
Figure 16 – Illustration of transient voltages on paired conductor external circuits . 48
Figure 17 – Illustration of transient voltages on coaxial-cable external circuits . 49
Figure 18 – Examples of transmission mode and applied conductors . 50
Figure 19 – Basic and reinforced insulation in Table 14; ratio reinforced to basic . 51
Figure 20 – Reinforced clearances according to Rule 1, Rule 2, and Table 14 . 53
Figure 21 – Example illustrating accessible internal wiring . 61
Figure 22 – Waveform on insulation without surge suppressors and no breakdown . 63
Figure 23 – Waveforms on insulation during breakdown without surge suppressors . 64
Figure 24 – Waveforms on insulation with surge suppressors in operation . 64
Figure 25 – Waveform on short-circuited surge suppressor and insulation . 64
Figure 26 – Normal operating condition. 66
Figure 27 – Single fault condition . 66
Figure 28 – Single fault condition; hazardous situation if 5.4.11 is not fulfilled . 67
Figure 29 – Parts earthed in one piece of equipment . 67
Figure 30 – Equipment 2 with connection to a network . 68
Figure 31 – Example for an ES2 source . 68
Figure 32 – Example for an ES3 source . 69
Figure 33 – Overview of protective conductors . 71
Figure 34 – Example of a typical touch current measuring network . 74
Figure 35 – Touch current from a floating circuit . 76
Figure 36 – Touch current from an earthed circuit . 76
Figure 37 – Summation of touch currents in a PABX . 77
Figure 38 – Possible safeguards against electrically-caused fire . 84
Figure 39 – Fire clause flow chart . 87
Figure 40 – Prevent ignition flow chart . 93
Figure 41 – Control fire spread summary . 94
Figure 42 – Control fire spread PS2 . 95
Figure 43 – Control fire spread PS3 . 96
Figure 44 – Fire cone application to a large component . 105
Figure 45 – Calculation of side opening size . 112
Figure 46 – Flowchart demonstrating the hierarchy of hazard management . 118
Figure 47 – Model for chemical injury. 119
Figure 48 – Direction of forces to be applied . 123
Figure 49 – Model for a burn injury . 127
Figure 50 – Model for safeguards against thermal burn injury . 129
Figure 51 – Model for absence of a thermal hazard. 129
Figure 52 – Model for presence of a thermal hazard with a physical safeguard in place . 129
Figure 53 – Model for presence of a thermal hazard with behavioural safeguard in
place . 130
Figure 54 – Direct plug in . 132
Figure 55 – External power supply . 132
Figure 56 – Examples of symmetrical single coils . 137
Figure 57 – LED parameters . 137
Figure 58 – Flowchart for evaluation of Image projectors (beamers) . 139
Figure 59 – Graphical representation of L ,T . 141
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Figure 60 – Overview of operating modes . 148
Figure 61 – Typical examples of class I equipment . 151
Figure 62 – Typical examples of class I equipment with class II construction . 152
Figure 63 – Typical examples of class II equipment . 153
Figure 64 – Typical examples of class II equipment with functional earth . 154
Figure 65 – Typical examples of class II equipment with functional earth, making use of
a class I mains connector . 155
Figure 66 – Typical examples of class II equipment with functional earth, making use of
a class I mains connector and a separate functional earthing connection . 156
Figure 67 – Voltage-current characteristics (Typical data) . 158
Figure 68 – Example of IC current limiter circuit . 163
Figure 69 – Example of application of Rule 3, first dash . 165
Figure 70 – Example of application of Rule 3, second dash . 166
Figure 71 – Example on how to use Table G.12 . 166
Figure 72 – Decision flowchart . 168
Figure 73 – Illustration of a self-contained LFC system . 170
Figure 74 – Illustration of a modular LFC system . 171
Figure 75 – Example illustration of a rack modular LFC subsystems with internal and
external connections. . 172
Figure 76 – CDU liquid cooling system within a data centre . 173
Figure 77 – Non-CDU liquid cooling system within data centre . 173
Figure 78 – Current limit curves . 175
Figure 79 – Example of a dummy battery circuit . 187
Figure 80 – Calculating side openings . 191
Figure 81 – Example of a circuit with two power sources . 193
Figure A.1 – Installation has poor earthing and bonding; equipment damaged
(from ITU-T Recommendation K.66) . 201
Figure A.2 – Installation has poor earthing and bonding; using main earth bar for
protection against lightning strike (from ITU-T Recommendation K.66) . 201
Figure A.3 – Installation with poor earthing and bonding, using a varistor . 202
Figure A.4 – Typical example of a surge suppressor and a voltage fall . 202
Figure A.5 – An example of surge voltage drop by an MOV and two GDTs (measured
in laboratory) . 204
Figure A.6 – An example of ports of telecommunication equipment . 208
Figure A.7 – V-I properties of gas discharge tubes . 210
Figure A.8 – Holdover . 211
Figure A.9 – Relation of the V-I characteristic of a gas discharge tube and the output
characteristic of the power supply . 212
Figure A.10 – V-I and V-t characteristics . 213
Figure A.11 – Follow-on current pictures . 214
Figure B.1 – Typical EMC filter schematic . 215
Figure B.2 – 100 MΩ oscilloscope probes . 217
Figure B.3 – Combinations of EUT resistance and capacitance for 1 s time constant . 219
Figure B.4 – 240 V mains followed by capacitor discharge . 221
Figure B.5 – Time constant measurement schematic . 222
Figure B.6 – Worst-case measured time constant values for 100 MΩ and 10 MΩ probes . 226
Figure D.1 – Example of circuit configuration of a surge suppresser . 228

Table 1 – General summary of required safeguards . 22
Table 2 – Time/current zones for AC 15 Hz to 100 Hz for hand to feet pathway (see
IEC 60479-1:2018, Table 11) . 30
Table 3 – Time/current zones for DC for hand to feet pathway (see IEC 60479-1:2018,
Table 13) . 31
Table 4 – Limit values of accessible capacitance (threshold of pain) . 34
Table 5 – Total body resistances R for a current path hand to hand, DC, for large
T
surface areas of contact in dry condition . 36
Table 6 – Insulation requirements for external circuits . 49
Table 7 – Voltage drop across clearance and solid insulation in series . 55
Table 8 – Examples of application of various safeguards . 86
Table 9 – Basic safeguards against fire under normal operating conditions and
abnormal operating conditions . 89
Table 10 – Supplementary safeguards against fire under single fault conditions . 90
Table 11 – Method 1: Reduce the likelihood of ignition . 92
Table 12 – Method 2: Control fire spread . 100
Table 13 – Fire barrier and fire enclosure flammability requirements . 107
Table 14 – Summary – Fire enclosure and fire barrier material requirements . 111
Table 15 – Control of chemical hazards . 117
Table 16 – Overview of requirements for dose-based systems . 143
Table 17 – Overview of supply voltage . 147
Table 18 – Safety of batteries and their cells – requirements (expanded information on
documents and scope) . 180
Table A.1 – Permissible power-frequency stress voltage (except for US and Japan) . 204
Table A.2 – TOV parameters for US systems quoted from IEC 61643-12:2020 . 205
Table A.3 – TOV test parameters for Japanese systems quoted from IEC 61643-
12:2020 . 205
Table A.4 – Peak voltage of TOV in countries conforming to IEC 60364-4-44 . 206
Table A.5 – Peak voltage of TOV in USA . 206
Table A.6 – Peak voltage of TOV in Japan . 206
Table A.7 – The value of U for major mains voltages . 207
peak2
Table B.1 – 100 MΩ oscilloscope probes . 217
Table B.2 – Capacitor discharge . 218
Table B.3 – Maximum T values for combinations of R and C for
measured EUT EUT
T of 1 s . 225
EUT
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Audio/video, information and communication technology equipment -
Part 2: Explanatory information related to IEC 62368-1:2023

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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shall not be held responsible for identifying any or all such patent rights.
IEC TR 62368-2 has been prepared by IEC technical committee TC 108: Safety of electronic
equipment within the field of audio/video, information technology and communication
technology. It is a Technical Report.
This fourth edition cancels and replaces the third edition published in 2018. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) It takes into account changes made in the fourth edition of IEC 62368-1 (IEC 62368-1:2023)
as identified in the Foreword of IEC 62368-1:2023.
The text of this Technical Report is based on the following documents:
Draft Report on voting
108/794/DTR 108/825/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
In this document, the following print types are used:
– notes/explanatory matter: in smaller roman type;
– tables and figures that are included in the rationale have linked fields (shaded in grey if
“field shading” is active);
– terms that are defined in IEC 62368-1: in bold type.
Where coloured shading is used:
– green colour stands for level 1 energy sources
– yellow/orange colour stands for level 2 energy sources
– red colour stands for level 3 energy sources.
In this document, where the term (HBSDT) is used, it stands for Hazard Based Standard
Development Team, which is the Working Group of IEC TC 108 responsible for the development
and maintenance of IEC 62368-1.
A list of all parts of the IEC 62368 series can be found, under the general title Audio/video,
information and communication technology equipment, on the IEC website.
In this document, only those subclauses from IEC 62368-1 considered to need further
background reference information or explanation to benefit the user in applying the relevant
requirements are included. Therefore, not all numbered subclauses are cited. Unless otherwise
noted, all references are to clauses, subclauses, annexes, figures or tables located in
IEC 62368-1:2023.
The entries in this document can have one or two of the following subheadings in addition to
the Rationale statement:
Source – where the source is known and is a document that is accessible to the general public,
a reference is provided.
Purpose – where there is a need and when it can prove helpful to the understanding of the
Rationale, a Purpose statement has been added.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
INTRODUCTION
IEC 62368-1 is based on the principles of hazard-based safety engineering, which is a different
way of developing and specifying safety considerations than that of the current practice. While
IEC 62368-1 is different from traditional IEC safety documents in its approach and while it is
believed that IEC 62368-1 provides a number of advantages, its introduction and evolution are
not intended to result in significant changes to the existing safety philosophy that led to the
development of the safety requirements contained in IEC 60065 and IEC 60950-1. The
predominant reason behind the creation of IEC 62368-1 is to simplify the problems created by
the merging of the technologies of ITE and CE. The techniques used are novel, so a learning
process and experience in its application are needed.

0 Principles of this product safety standard
Clause 0 is informative and provides a rationale for the normative clauses of
IEC 62368-1:2023.
0.5.1 General
ISO/IEC Guide 51:2014, 6.3.5 states:
“When reducing risks, the order of priority shall be as follows:
a) inherently safe design;
b) guards and protective devices;
c) information for end users.
Inherently safe design measures are the first and most important step in the risk
reduction process. This is because protective measures inherent to the
characteristics of the product or system are likely to remain effective, whereas
experience has shown that even well-designed guards and protective devices
can fail or be violated and information for use might not be follo
...