TC 31 - Equipment for explosive atmospheres

IEC 60079:2024 contains the specific requirements for the design of electrical systems, selection, installation and the required initial inspection of electrical installations of Ex Equipment in, or associated with, explosive atmospheres including requirements for documentation and personnel competency.
These requirements are in addition to the requirements for installations in non-hazardous areas.
This document applies to all electrical Ex Equipment including fixed, transportable, portable and personal, and installations, permanent or temporary.
This document does not apply to:
• electrical installations in mines susceptible to firedamp;
• inherently explosive situations and dust from explosives or pyrophoric substances (for example explosives manufacturing and processing);
• rooms used for medical purposes;
• electrical installations in areas where the hazard is due to flammable mist; and
• installation of non-electrical Ex Equipment (unless being part of an equipment assembly according IEC TS 60079-46).
No account is taken in this document of the toxic hazards that are associated with flammable gases, liquids and dusts in concentrations that are usually very much less than the lower flammable limit. In locations where personnel could be exposed to potentially toxic concentrations of flammable material, appropriate precautions are necessary. Such precautions are outside the scope of this document.
This sixth edition cancels and replaces the fifth edition published in 2013. This edition constitutes a technical revision. Edition 6 is a major restructure and introduces a number of technical changes from the previous edition (2013), see Table 1 of the foreword for detailed information.

ISO/IEC 80079-49:2024 specifies the requirements for flame arresters that prevent flame transmission when explosive gas-air or vapour-air mixtures are present. It establishes uniform principles for the classification, basic construction and information for use, including the marking of flame arresters, and specifies test methods to verify the safety requirements and determine safe limits of use.
This document is applicable to pressures ranging from 80 kPa to 160 kPa and temperatures ranging from -20 °C to +200 °C.
This document does not apply to the following:
- external safety-related measurement and control equipment that might be required to keep the operational conditions within the established safe limits;
- flame arresters used for explosive mixtures of vapours and gases, which tend to self-decompose (for example, acetylene) or which are chemically unstable;
- flame arresters used for carbon disulfide, due to its special properties;
- flame arresters whose intended use is for mixtures other than gas-air or vapour-air mixtures (for example, higher oxygen-nitrogen ratio, chlorine as oxidant);
- flame arrester test procedures for reciprocating internal combustion engines;
- fast acting valves, extinguishing systems and other explosion isolating systems;
- Flame arresters used in gas detectors (those being covered for example, by IEC 60079‑29‑1 and IEC 62990‑1).
This edition cancels and replaces ISO 16852:2016, which has been technically revised. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to ISO 16852:2016:
a) adaptation of the relevant IEC TC 31 requirements on standards;
b) modification of the upper limit of the temperature range from 150 °C to 200 °C under the condition that T0 shall be not larger than 80 % of the auto ignition temperature of the gas-air-mixture;
c) change of the term "explosion group" to "equipment group" due to editorial requirements in IEC/TC 31;
d) clarification of the conditions and requirements for flame arresters whose intended operating conditions are outside the atmospheric conditions in 7.3.4 and 7.3.5;
e) clarification of the requirements on the information for use in Clause 12 f) concerning the burn time;
f) addition of a permission to the construction requirements both in 7.1 and 14.1 to substitute visual inspection by performing a flow test;
g) addition of a flow chart for the evaluation of test results as Annex D

IEC 60079-17:2023 applies to users and covers only those factors directly related to the inspection and maintenance of electrical installations specifically designed for hazardous areas, where the hazard is caused by explosive atmospheres.
It does not include:
- other fundamental installation and inspection requirements for electrical installations;
- the verification of electrical equipment;
- protection or ventilation of rooms;
- gas detection systems;
- the repair, overhaul and reclamation of explosion protected equipment (see IEC 60079-19).
While this document does not include inspection of safety devices such as used in ventilated rooms (see IEC 60079-13), it does include the requirements for inspection and maintenance of individual items of equipment that will be part of such systems, for example motors or sensors. This document supplements the requirements for inspection and testing in non-hazardous areas in IEC 60364-6. This document is intended to be applied where there is a risk due to the potential presence of explosive gas or dust mixtures with air or combustible dust layers under normal atmospheric conditions. It does not apply to:
- underground mining areas,
- dusts of explosives,
- pyrophoric substances.
This sixth edition cancels and replaces the fifth edition published in 2013. This edition constitutes a technical revision.

IEC TS 60079-44:2023, which is a Technical Specification, is to provide guidance to establish recommended minimum criteria to determine roles, establish expectations of the necessary skills and evidence of competence to assess and manage the competence of personnel conducting work in or associated with hazardous areas. The purpose of this document is to provide guidance to establish:
• recommended minimum criteria to determine roles,
• expectations of the necessary skills, and
• evidence of competence
in order to assess and manage the competence of personnel who are conducting work in or associated with hazardous areas.
This document provides examples and recommendations of minimum levels of competence for typical roles associated with hazardous areas by addressing the knowledge, skills, or abilities that is expected of personnel. Additionally, examples of the evidence of competence expected for each role are provided.
The aim of tThis document is to assist in defining, assessing, and managing unique requirements for the competence of individuals working in or associated with installations where an explosive atmosphere could be present. Such a programme could be specific to a facility or used in conjunction with other regulatory requirements where they exist. The competencies for conducting work in a hazardous area are in addition to any competencies which may apply for the general type of work being undertaken (for example, professional credentials, electrical, non-electrical, operations, design).
This document applies to both electrical and non-electrical applications.
This document identifies the minimum level of knowledge and skills required to work in hazardous areas and the specific competence required for work associated with equipment for explosive atmospheres (commonly termed ‘Ex Equipment’) and the standards to which competence is to be assessed and attributed.
The purpose of this document is to provide guidance to establish:
• recommended minimum criteria to determine roles,
• expectations of the necessary skills, and
• evidence of competence
The principal application of this specification document is for personnel dealing with explosion-protected and associated equipment for use in explosive atmospheres, including the following work functions:
• Classification of areas;
• Producing, processing or servicing functions in a hazardous area and not directly involved in installing, maintaining or repairing explosion-protected equipment and systems;
• Designing, commissioning and maintaining explosion-protection strategies and equipment;
• Selecting, installing, testing and maintaining explosion-protected equipment and systems in hazardous areas;
• Inspecting hazardous area equipment, systems and installations;
• Overhauling, repairing and modifying explosion-protected equipment;
• Management of the Ex aspects of the facility.

IEC 60079-48:2023, which is a Technical Specification, provides guidance for an owner or operator for the use of portable or personal electronic equipment to be used in hazardous areas requiring Equipment Protection Level (EPL) Gb, Gc, Db, or Dc that are not otherwise commercially available with a certificate.
This document does not apply to:
• equipment that is electrically connected to fixed equipment or fixed wiring during use in the hazardous area, for example a lead light connected to the premises wiring system by a plug and socket,
• portable or personal equipment with a certificate for use in a hazardous area,
• transportable equipment,
• portable or personal equipment used in Group I applications,
• battery powered tools, such as drills and saws,
• portable or personal equipment used in areas requiring EPL Ga or Da equipment, or,
• medical devices.
This document does not address other considerations involving the use of portable or personal electronic equipment for other aspects of safety, for example, creation of a distraction from important work tasks, radio frequency interference with measurement and control equipment, or medical issues.
This document supplements the guidance in IEC 60079-14 regarding the use of personal or portable equipment without a certificate for use in hazardous areas.

IEC 60079-11:2023 specifies the construction and testing of intrinsically safe apparatus intended for use in explosive atmospheres, and for associated apparatus which is intended for connection to intrinsically safe circuits which enter such atmospheres.
This Type of Protection is applicable to electrical equipment in which the electrical circuits themselves are incapable of causing ignition of a surrounding explosive atmosphere. This includes electrical equipment which contains circuits that are intrinsically safe only under certain conditions, for example under battery supply with mains supply removed.
This document is also applicable to electrical equipment or parts of electrical equipment located outside the explosive atmosphere or protected by another Type of Protection listed in IEC 60079 0, where the intrinsic safety of the electrical circuits in the explosive atmosphere may depend upon the design and construction of such electrical equipment or parts of such electrical equipment. The electrical circuits exposed to the explosive atmosphere are assessed for use in such atmospheres by applying this document.
This document applies to sensors connected to intrinsically safe circuits but does not apply to the protection of catalytic elements for Group IIC or Group IIB + H2.
This document does not apply to Ex Equipment cable glands.
The requirements for intrinsically safe systems are provided in IEC 60079-25.
This document supplements and modifies the general requirements of IEC 60079-0, except as indicated in Table 1. Where a requirement of this document conflicts with a requirement of IEC 60079-0, the requirement of this document takes precedence.
Unless otherwise stated, the requirements in this document are applicable to both intrinsically safe apparatus and associated apparatus, and the generic term "apparatus" is used throughout the standard.
As this document applies only to electrical equipment, the term "equipment" used in the standard always means "electrical equipment".
This document applies to apparatus for use under the atmospheric conditions of IEC 60079 0 with additional requirements for use at extended atmospheric pressures in the range from 60 kPa (0,6 bar), up to 110 kPa (1,1 bar).
This seventh edition cancels and replaces the sixth edition published in 2011. This edition constitutes a technical revision.
The identification and significance of the changes between IEC 60079-11, Edition 7 (2022) and IEC 60079-11, Edition 6 (2011 + Corrigendum 1 (2012)) can be found in the table of changes in the foreword of the publication.
The contents of the corrigendum 1 (2023-06), the Interpretation sheets 1 (2024-05), 2 (2024-05) and 3 (2024-08) have been included in this copy.

IEC 60079-5:2015 contains specific requirements for the construction, testing and marking of electrical equipment, parts of electrical equipment and Ex components in the type of protection powder filling "q", intended for use in explosive gas atmospheres. This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard takes precedence. This standard applies to electrical equipment, parts of electrical equipment and Ex components with:
- a rated supply current less than or equal to 16 A;
- a rated supply voltage less than or equal to 1 000 V;
- a rated power consumption less than or equal to 1 000 W. This fourth edition cancels and replaces the third edition, published in 2007, and constitutes a technical revision. Refer to the Foreword of the document for a complete listing of the technical changes between edition 4.0 and previous edition of the document. Keywords: electrical equipment and Ex components in the type of protection powder filling "q"

IEC 60079-31:2022 is applicable to equipment protected by enclosure and surface temperature limitation for use in explosive dust atmospheres. It specifies requirements for design, construction and testing of Ex Equipment and Ex Components. This document supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this document conflicts with a requirement of IEC 60079-0, the requirement of this document takes precedence. This document does not apply to dusts of explosives, which do not require atmospheric oxygen for combustion, or to pyrophoric substances. This document does not apply to Ex Equipment or Ex Components intended for use in underground parts of mines as well as those parts of surface installations of such mines endangered by firedamp and/or combustible dust. This document does not take account of any risk due to an emission of flammable or toxic gas from the dust. This third edition cancels and replaces the second edition published in 2013. This edition constitutes a technical revision. Main significant changes from the previous edition are:
1) Document has been restructured from edition 2
2) Fault current rating of interrupting contacts in clauses 4.3.1 and 4.4.1, major change type C1
3) Cells and batteries in clauses 4.3.5.1 and 4.4.5.1, major change type C2
4) Overload or malfunction condition for the determination of temperature class for "tb" converter fed rotating electric machines, major change type C3
5) Additional requirements for entry devices with dust ignition protection by enclosure "t", major change type C4
Information about the background of ‘Major Technical Changes’
C1 – Ex Equipment having Level of Protection "ta" shall be rated for connection to a circuit with a prospective short circuit current of not greater than 1.5 kA. For Ex Equipment having Level of Protection "tb" or "tc" which is intended for mains connection and intended to interrupt fault current above 10kA, the equipment shall have a rated maximum short circuit withstand current, be tested according to 6.1.1.1, and be marked according to Clause 7.
C2 – For Ex Equipment having Level of Protection "ta" which contains a cell or battery, only a sealed cell or battery shall be used. For Ex Equipment having Level of Protection "tb" and "tc" where there are sparking contacts or hot surfaces, and which contains a cell or battery, only a sealed cell or battery shall be used.
C3 – Table 2 now includes malfunction conditions for temperature class determination of Level of Protection "tb" converter-fed electric machines.
C4 – Annex A added for entry devices with Type of Protection "t" including cable transit devices.
The contents of the corrigendum of October 2023 have been included in this copy.

IEC 62990-2:2021 gives guidance on the selection, installation, use and maintenance of electrical equipment used for the measurement of toxic gases and vapours in workplace atmospheres. The primary purpose of such equipment is to ensure safety of personnel and property by providing an indication of the concentration of a toxic gas or vapour and warning of its presence.
This document is applicable to equipment whose purpose is to provide an indication, alarm or other output function to give a warning of the presence of a toxic gas or vapour in the atmosphere and in some cases to initiate automatic or manual protective actions. It is applicable to equipment in which the sensor automatically generates an electrical signal when gas is present.
For the purposes of this document, equipment includes:
a) fixed equipment;
b) transportable equipment, and
c) portable equipment.
This document is intended to cover equipment defined within IEC 62990-1, but can provide useful information for equipment not covered by that document.

IEC 60079-10-1:2020 is concerned with the classification of areas where flammable gas or vapour hazards may arise and may then be used as a basis to support the proper design, construction, operation and maintenance of equipment for use in hazardous areas.
It is intended to be applied where there may be an ignition hazard due to the presence of flammable gas or vapour, mixed with air, but it does not apply to:
a) mines susceptible to firedamp;
b) the processing and manufacture of explosives;
c) catastrophic failures or rare malfunctions which are beyond the concept of normality dealt with in this standard;
d) rooms used for medical purposes;
e) domestic premises;
f) where a hazard may arise due to the presence of combustible dusts or combustible flyings but the principles may be used in assessment of a hybrid mixture.
Flammable mists may form or be present at the same time as flammable vapour. In such case the strict application of the details in this document may not be appropriate. Flammable mists may also form when liquids not considered to be a hazard due to the high flash point are released under pressure. In these cases the classifications and details given in this document do not apply.
For the purpose of this document, an area is a three-dimensional region or space.
Atmospheric conditions include variations above and below reference levels of 101,3 kPa (1 013 mbar) and 20 °C (293 K), provided that the variations have a negligible effect on the explosion properties of the flammable substances.
In any site, irrespective of size, there may be numerous sources of ignition apart from those associated with equipment. Appropriate precautions will be necessary to ensure safety in this context. This standard is applicable with judgement for other ignition sources but in some applications other safeguards may also need to be considered. E.g. larger distances may apply for naked flames when considering hot work permits.
This document does not take into account the consequences of ignition of an explosive atmosphere except where a zone is so small that if ignition did occur it would have negligible consequences.
This third edition of IEC 60079-10-1 cancels and replaces the second edition, published in 2015, and constitutes a technical revision, see foreword for further details.

IEC 60079-26:2021 specifies requirements for construction, testing and marking for Ex Equipment that contains parts of the equipment with different Equipment Protection Levels (EPLs) and a separation element. This equipment is mounted across a boundary where different EPLs are required, for example between different gas hazardous areas, dust hazardous areas or gas hazardous areas adjacent to dust hazardous areas.
Separation elements are considered for both electrical and non-electrical equipment. If mechanical energy can be transformed into a potential ignition source, additionally an ignition hazard assessment in accordance with ISO 80079-36 is performed and appropriate measures are undertaken.
This document also specifies requirements for the combination of two Types of Protection, each with EPL Gb, to achieve EPL Ga.
This document supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this document conflicts with a requirement of IEC 60079-0, the requirement of this document takes precedence. This fourth edition cancels and replaces the third edition and constitutes a technical revision.
Please see the IEC 60079-26:2020 foreword for a description of the main changes with respect to the previous edition.

IEC 60079-47:2021(E), which is a technical specification, specifies requirements for the construction, marking and documenting of apparatus, systems and installations for use with the 2-Wire Intrinsically Safe Ethernet concept (2-WISE), such as the physical layer specification for 2-Wire Ethernet 10BASE-T1L as defined in IEEE 802.3cg.
2-WISE is a concept for an advanced physical layer (APL), designed to simplify the examination process for intrinsic safety parameters of components and cabling within APL segments. This is achieved by defining universal intrinsic safety parameter limits for APL ports, according to the specific hazardous area requirements and listing a concise set of rules for the segment setup.
The requirements for construction and installation of 2-WISE devices and systems are included in IEC 60079-11, IEC 60079-14, and IEC 60079-25, except as modified by this document. Parts of a 2-WISE device can be protected by any Type of Protection listed in IEC 60079-0 appropriate to the EPL for the intended hazardous area. In these circumstances, the requirements of this technical specification apply only to intrinsically safe circuits of the apparatus.
Where a requirement of this document conflicts with a requirement of IEC 60079-0, IEC 60079 11, IEC 60079-14 or IEC 60079-25, the requirements of this document take precedence.

IEC 60079-25:2020 contains the specific requirements for design, construction and assessment of intrinsically safe systems, Type of Protection “i”, intended for use, as a whole or in part, in locations in which the use of Group I, II or III Ex Equipment is required.
This document supplements and modifies the general requirements of IEC 60079-0 and the intrinsic safety standard IEC 60079-11. Where a requirement of this standard conflicts with a requirement of IEC 60079-0 or IEC 60079-11, the requirement of this standard takes precedence.
The installation requirements of Group II or Group III systems designed in accordance with this standard are specified in IEC 60079-14.
This third edition cancels and replaces the second edition published in 2010 and constitutes a technical revision.
The contents of the corrigendum 1 of October 2020 and corrigendum 2 of November 2022 have been included in this copy.

IEC 60079-29-1:2016 specifies general requirements for construction, testing and performance, and describes the test methods that apply to portable, transportable and fixed equipment for the detection and measurement of flammable gas or vapour concentrations with air. The equipment, or parts thereof, is intended for use in explosive atmospheres and in mines susceptible to firedamp. This second edition of IEC 60079-29-1 cancels and replaces the first edition of IEC 60079-29-1:2007 series and constitutes a technical revision. Refer to the Forward of the document for a listing of the extensive changes between this edition and the previous edition. Keywords: detection and measurement of flammable gas or vapour concentrations with air, explosive atmospheres, mines susceptible to firedamp, explosion hazard
The contents of the interpretation sheets 1 and 2 (2019-04) have been included in this copy.

IEC 60050-426:2020 gives terms specifically relevant to explosive atmospheres. This new edition reviews and complements the previous one. This terminology is consistent with the terminology developed in the other specialized parts of the IEV.
It has the status of a horizontal standard in accordance with IEC Guide 108.

IEC 60079-6:2015 specifies the requirements for the design, construction, testing and marking of Ex Equipment and Ex Components with type of protection liquid immersion "o" intended for use in explosive gas atmospheres. Ex Equipment and Ex Components of type of protection liquid immersion "o" are either:
- Level of Protection "ob" (EPL "Mb" or "Gb") or
- Level of Protection "oc" (EPL "Gc"). For Level of Protection "ob", this standard applies where the rated voltage does not exceed 11 kV r.m.s. a.c. or d.c. For Level of Protection "oc", this standard applies where the rated voltage does not exceed 15 kV r.m.s. a.c. or d.c. This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard takes precedence. This fourth edition cancels and replaces the third edition, published in 2007. This edition constitutes a technical revision. The significant changes with respect to the previous edition are:
- Edition 4 represents a major technical revision of the requirements for oil immersion "o" and should be considered as introducing all new requirements. The normal "Table of Significant Changes" has not been included for this reason. In particular:
- The requirements for oil immersion "o" have been redefined into liquid immersion, levels of protection "ob" and "oc" as recommended by the responses to 31/715/DC;
- The ability to protect sparking contacts has been added to both "ob" and "oc". Additional requirements have been introduced for the protective liquid. Keywords: Ex Equipment and Ex Components with type of protection liquid immersion "o"

IEC 60079-19:2019 gives instructions, principally of a technical nature, on the repair, overhaul, reclamation and modification of equipment designed for use in explosive atmospheres; it is not applicable to maintenance, other than when repair and overhaul cannot be disassociated from maintenance, neither does it give advice on cable entry systems which may require a renewal when the equipment is re-installed.
This fourth edition cancels and replaces the third edition published in 2010 together with Amendment 1:2015. This edition constitutes a technical revision.
The significance of the changes between IEC 60079-19, Edition 3 (2010), including Amendment 1 (2015), and IEC 60079-19, Edition 4 (2019) are defined in the foreword and cover minor and editorial changes, extension, and major technical changes.

IEC 62990-1:2019 specifies general requirements for design, function and performance, and describes the test methods that apply to portable, transportable, and fixed equipment for the detection and concentration measurement of toxic gases and vapours in workplace atmospheres and other industrial and commercial applications.
This document is applicable to continuously sensing equipment whose primary purpose is to provide an indication, alarm and/or other output function the purpose of which is to indicate the presence of a toxic gas or vapour in the atmosphere and in some cases to initiate automatic or manual protective action(s). It is applicable to equipment in which the sensor generates an electrical signal when gas is present.
This document applies to two types of equipment:
• Type HM (Health Monitoring) ‘occupational exposure’ equipment:
For occupational exposure measurement, the performance requirements are focused on uncertainty of measurement of gas concentrations in the region of Occupational Exposure Limit Values (OELV). The upper limit of measurement will be defined by the manufacturer in accordance with 4.2.1.
• Type SM (Safety Monitoring) ‘general gas detection’ equipment:
For general gas detection applications (e.g. safety warning, leak detection), the performance requirements are focused on alarm signalling. The upper limit of measurement will be defined by the manufacturer according to the intended use of the equipment.
In general, the requirements for accuracy will be higher for Type HM equipment than for Type SM equipment. The same equipment may meet the requirements of both Type HM and Type SM.
For equipment used for sensing the presence of multiple gases this document applies only to the detection of toxic gas or vapour.
This document is not applicable to equipment:
- with samplers and concentrators such as sorbents or paper tape having an irreversible indication;
- used for the measurement of gases and vapours related to the risk of explosion;
- used for the measurement of oxygen;
- used only in laboratories for analysis or measurement;
- used only for process measurement purposes;
- used in the domestic environment;
- used in environmental air pollution monitoring;
- used for open-path (line of sight) area gas measurement;
- used for ventilation control in car parks or tunnels.
The contents of the corrigendum of December 2019 have been included in this copy.

IEC TS 60079-42:2019 provides guidance for equipment manufacturers where electrical safety devices are used to reduce the likelihood of potential ignition sources becoming effective in Ex Equipment located in Explosive Atmospheres. Electrical safety devices perform a safety function to control potential ignition sources from both, electrical or non-electrical Ex Equipment in explosive atmospheres.
This Technical Specification may also be applied to a combination of elements performing a safety function. For example: Sensor, Logic system, Final element. This Technical Specification can also be used for assessing the safety device independently, without being designed for a specific Ex Equipment. A safety device can be a measure to achieve a required EPL of the Ex Equipment with respect to a potential ignition source. The combination of the safety device and the Ex Equipment could then comply with the relevant standards of the IEC 60079 series and the ISO 80079 series with respect to the Equipment Protection Level. However, increasing the EPL of Ex Equipment by the simple addition of a safety device is not within the scope of this Technical Specification.
This Technical Specification does not apply to:
• mechanical control equipment such as pressure relief valves, mechanical governors and other mechanical safety devices
• the use of gas detection
• control equipment to prevent the occurrence of explosive atmospheres, e.g. inerting systems and ventilation systems
• mitigation of an explosion