CAN/CSA-C22.2 No. 61508-1:17
Functional safety of electrical/electronic/programmable electronic safetyrelated systems — Part 1: General requirements
1.1 This International Standard covers those aspects to be considered when
electrical/electronic/programmable electronic (E/E/PE) systems are used to carry out safety
functions. A major objective of this standard is to facilitate the development of product and
application sector international standards by the technical committees responsible for the
product or application sector. This will allow all the relevant factors, associated with the product
or application, to be fully taken into account and thereby meet the specific needs of users of
the product and the application sector. A second objective of this standard is to enable the
development of E/E/PE safety-related systems where product or application sector international
standards do not exist.
1.2 In particular, this standard
a) applies to safety-related systems when one or more of such systems incorporates
electrical/electronic/programmable electronic elements;
NOTE 1 In the context of low complexity E/E/PE safety-related systems, certain requirements specified in this
standard may be unnecessary, and exemption from compliance with such requirements is possible (see 4.2, and
the definition of a low complexity E/E/PE safety-related system in 3.4.3 of IEC 61508-4).
NOTE 2 Although a person can form part of a safety-related system (see 3.4.1 of IEC 61508-4), human factor
requirements related to the design of E/E/PE safety-related systems are not considered in detail in this standard.
b) is generically-based and applicable to all E/E/PE safety-related systems irrespective of the
c) covers the achievement of a tolerable risk through the application of E/E/PE safety-related
systems, but does not cover hazards arising from the E/E/PE equipment itself (for example
d) applies to all types of E/E/PE safety-related systems, including protection systems and
e) does not cover E/E/PE systems where
– a single E/E/PE system is capable on its own of meeting the tolerable risk, and
– the required safety integrity of the safety functions of the single E/E/PE system is less
than that specified for safety integrity level 1 (the lowest safety integrity level in this
f) is mainly concerned with the E/E/PE safety-related systems whose failure could have an
impact on the safety of persons and/or the environment; however, it is recognized that the
consequences of failure could also have serious economic implications and in such cases
this standard could be used to specify any E/E/PE system used for the protection of
equipment or product;
NOTE 3 See 3.1.1 of IEC 61508-4.
g) considers E/E/PE safety-related systems and other risk reduction measures, in order that
the safety requirements specification for the E/E/PE safety-related systems can be
determined in a systematic, risk-based manner;
h) uses an overall safety lifecycle model as the technical framework for dealing systematically
with the activities necessary for ensuring the functional safety of the E/E/PE safety-related
NOTE 4 Although the overall safety lifecycle is primarily concerned with E/E/PE safety-related systems, it could
also provide a technical framework for considering any safety-related system irrespective of the technology of that
system (for example mechanical, hydraulic or pneumatic).
i) does not specify the safety integrity levels required for sector applications (which must be
based on detailed information and knowledge of the sector application). The technical
committees responsible for the specific application sectors shall specify, where appropriate,
the safety integrity levels in the application sector standards;
j) provides general requirements for E/E/PE safety-related systems where no product or
application sector international standards exist;
k) requires malevolent and unauthorised actions to be considered during hazard and risk
analysis. The scope of the analysis includes all relevant safety lifecycle phases;
NOTE 5 Other IEC/ISO standards address this subject in depth; see ISO/IEC/TR 19791 and IEC 62443 series.
l) does not cover the precautions that may be necessary to prevent unauthorized persons
damaging, and/or otherwise adversely affecting, the functional safety of E/E/PE safetyrelated
systems (see k) above);
m) does not specify the requirements for the development, implementation, maintenance
and/or operation of security policies or security services needed to meet a security policy
that may be required by the E/E/PE safety-related system;
n) does not apply for medical equipment in compliance with the IEC 60601 series.
1.3 This part of the IEC 61508 series of standards includes general requirements that are
applicable to all parts. Other parts of the IEC 61508 series concentrate on more specific topics:
– parts 2 and 3 provide additional and specific requirements for E/E/PE safety-related
systems (for hardware and software);
– part 4 gives definitions and abbreviations that are used throughout this standard;
– part 5 provides guidelines on the application of part 1 in determining safety integrity levels,
by showing example methods;
– part 6 provides guidelines on the application of parts 2 and 3;
– part 7 contains an overview of techniques and measures.
1.4 IEC 61508-1, IEC 61508-2, IEC 61508-3 and IEC 61508-4 are basic safety publications,
although this status does not apply in the context of low complexity E/E/PE safety-related
systems (see 3.4.3 of IEC 61508-4). As basic safety publications, they are intended for use
by technical committees in the preparation of standards in accordance with the principles
contained in IEC Guide 104 and ISO/IEC Guide 51. IEC 61508-1, IEC 61508-2, IEC 61508-3
and IEC 61508-4 are also intended for use as stand-alone publications. The horizontal safety
function of this international standard does not apply to medical equipment in compliance with
the IEC 60601 series.
NOTE One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety
publications in the preparation of its publications. In this context, the requirements, test methods or test conditions
of this basic safety publication will not apply unless specifically referred to or included in the publications prepared
by those technical committees.
1.5 Figure 1 shows the overall framework of the IEC 61508 series and indicates the role that
IEC 61508-1 plays in the achievement of functional safety for E/E/PE safety-related systems.
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