Before installing or inspecting any Ex equipment you must be able to read the certification marking, verify it against the area classification, and understand what the certificate conditions require. This unit covers the ATEX and IECEx frameworks, the full range of IEC 60079 standards, and how to interpret every element of an Ex nameplate.
Learning Objectives
State what ATEX 95 (Equipment Directive) and ATEX 137 (Workplace Directive) require
Distinguish between a Standard, a Code of Practice, and a Certification
Name the five key IEC 60079 codes of practice covering classification, installation, inspection, repair, and gas data
Identify the certification body code, year, and suffix in ATEX and IECEx certificate numbers
State what certificate suffix U and X mean and the action required for each
Read a complete ATEX equipment marking and identify every element
List the Equipment Protection Levels, their zones of use, and equivalent ATEX categories
Identify which types of protection are permitted in Zone 0, Zone 1, and Zone 2
EU Directives and ATEX
The two key ATEX directives are: ATEX 95 (Equipment Directive 94/9/EC) — sets requirements for Ex equipment manufactured and sold in the EU; and ATEX 137 (Workplace Directive 1999/92/EC) — sets requirements for employer safety management in potentially explosive atmospheres. In the UK, ATEX 137 is transposed by DSEAR (Dangerous Substances and Explosive Atmospheres Regulations).
Equipment certified to ATEX 95 carries the Ex hexagon symbol plus the CE mark. The Notified Body that performed certification has a unique number marked on the equipment (e.g. 1180 = Baseefa).
Standards and Codes of Practice
Construction standards define how equipment must be built. Codes of Practice define how it must be selected, installed, inspected, and maintained. Five IEC 60079 codes of practice replaced the old UK BS 5345:
ATEX certificate format: Baseefa 04 ATEX 0273 X — Notified Body, year, ATEX, serial number, suffix. IECEx format: IECEx BAS 06.0014X — scheme, body, year, serial, suffix.
Certificate Suffixes
U — Component certificate only. Not a finished product. Must be incorporated into a certified assembly before use. X — Special conditions of use apply. Read the certificate and verify compliance before installation.
Equipment Marking and EPLs
A complete ATEX marking: ⑇ II 2 G Ex d IIB T4 Gb
Element
Meaning
⑇
ATEX — EU Directive 2014/34/EU
II 2 G
Group II, Category 2, Gas — Zone 1 suitable
Ex d
Flameproof protection (IEC 60079-1)
IIB
Gas group — IIA and IIB atmospheres
T4
Max surface temperature 135°C
Gb
EPL — Zone 1 and 2 suitable
Zone Suitability by Protection Type
Zone
EPL
ATEX Cat
Permitted Protection Types
0
Ga
1
Ex ia, Ex ma only
1
Gb
2
All Zone 0 types + Ex d, Ex e, Ex ib, Ex mb, Ex o, Ex px, Ex py, Ex q
2
Gc
3
All Zone 1 types + Ex ic, Ex mc, Ex n (nA/nC/nR/nL), Ex pz
Quick Check — 5 Questions
Test key concepts from this unit before moving on.
Q1Summary
An ATEX certificate number ends in the suffix "U". What does this mean?
U means component certificate only. The item is not a complete product certified for use in a hazardous area — it must be incorporated into a further certified assembly. If installed alone, the installation is non-compliant.Ref: IEC 60079-0 / ATEX — Certificate Suffixes
Q2Summary
Which ATEX Category is suitable for Zone 1?
Zone 1 requires a minimum of Category 2 (EPL Gb). Category 1 (EPL Ga) is also acceptable — higher EPL equipment can always be used in less hazardous zones. Category 3 (EPL Gc) is Zone 2 only and must NOT be used in Zone 1.Ref: ATEX Directive 94/9/EC — Category System
Q3Summary
Which IEC 60079 standard covers the inspection and maintenance of electrical installations in hazardous areas?
IEC 60079-17 covers inspection and maintenance. IEC 60079-14 covers design, selection and erection. IEC 60079-19 covers repair and overhaul. IEC 60079-20 provides gas data.Ref: IEC 60079 Series — Codes of Practice
Q4Summary
An equipment nameplate reads: ⑇ II 2 G Ex e IIB T4 Gb. In which zones can it be installed?
EPL Gb (Category 2) is suitable for Zone 1 and Zone 2. Not Zone 0 — that requires EPL Ga (Category 1). The marking also shows Ex e (increased safety), IIB gas group, T4 temperature class.Ref: IEC 60079-0 — EPL and Zone Suitability
Q5Summary
An area classification drawing shows Zone 2, IIC, T4. Which is the MINIMUM acceptable EPL for equipment in this area?
Zone 2 requires minimum EPL Gc (Category 3). Higher EPL equipment (Gb or Ga) is also acceptable in Zone 2. The gas group (IIC) and T-class (T4) must also be verified — the EPL alone is not sufficient.Ref: IEC 60079-0 — EPL Table
EX Academy — independent CompEx-style preparation. Not official CompEx course materials.
Unit 2 · All Units · Full Manual
Standards, Certification & Equipment Marking
Before installing or inspecting any Ex equipment you must be able to read the certification marking, verify it against the area classification, and understand what the certificate conditions require. This unit covers the ATEX and IECEx frameworks, the full range of IEC 60079 standards, and how to interpret every element of an Ex nameplate.
Learning Objectives
State what ATEX 95 (Equipment Directive) and ATEX 137 (Workplace Directive) require
Distinguish between a Standard, a Code of Practice, and a Certification
Name the five key IEC 60079 codes of practice covering classification, installation, inspection, repair, and gas data
Identify the certification body code, year, and suffix in ATEX and IECEx certificate numbers
State what certificate suffix U and X mean and the action required for each
Read a complete ATEX equipment marking and identify every element
List the Equipment Protection Levels, their zones of use, and equivalent ATEX categories
Identify which types of protection are permitted in Zone 0, Zone 1, and Zone 2
2.2 EU Directives and ATEX
EU Directives remove technical barriers to trade by setting essential safety requirements that products must meet. For potentially explosive atmospheres, the relevant directives are the ATEX Directives. ATEX is an abbreviation from the French ATmosphères EXplosibles.
Any product sold in the EU must carry the CE mark, demonstrating compliance with all relevant directives including the Low Voltage Directive, the EMC Directive, and where applicable, the ATEX Directive. Two ATEX Directives apply to hazardous area work:
Governs equipment and protective systems intended for use in potentially explosive atmospheres. Sets requirements for: certification, quality assurance, and ongoing surveillance of the manufacturing process. Equipment complying with ATEX 95 carries the Ex hexagon symbol. The Directive defines three types of product: Equipment — machines, apparatus, control components capable of causing ignition through their own potential ignition source. Protective systems — systems intended to halt incipient explosions or limit their effects. Components — items essential to safe functioning but with no autonomous function.
ATEX 137 — Workplace Directive 1999/92/EC
Governs the health and safety of workers in places where explosive atmospheres may occur. Sets obligations on employers for: explosion risk assessment, explosion protection documents, zone classification, safe working procedures. Requires areas with potentially explosive atmospheres to be marked with a warning sign at all entry points. In the UK, transposed into law as DSEAR (Dangerous Substances and Explosive Atmospheres Regulations).
Although ATEX Directives are European, they are widely recognised worldwide. Many manufacturers outside the EU obtain ATEX certification to maximise market access. Equipment imported into the EU must meet ATEX 95 requirements regardless of origin.
2.3 Standards and Codes of Practice
Construction Standards
Define how equipment must be designed, built, and tested to provide the claimed protection concept. Published by IEC (international), CENELEC/EN (European), and BSI (UK). For explosion protection, IEC and European EN standards are now identical — published in the UK as BS EN 60079 series.
Codes of Practice
Define how equipment must be selected, installed, inspected, maintained, and repaired. In the UK, BS 5345 was the historic code of practice. It has been superseded by five international IEC 60079 documents.
The five key IEC 60079 Codes of Practice that replaced BS 5345:
Standard
Subject
Replaced
IEC 60079-10-1
Classification of hazardous areas — gases
BS 5345 Part 2
IEC 60079-14
Electrical installations design, selection and erection
BS 5345 Parts 1 & 4
IEC 60079-17
Inspection and maintenance of electrical installations
BS 5345 Part 1
IEC 60079-19
Repair and overhaul of Ex equipment
Various
IEC 60079-20-1
Data for flammable gases and vapours
BS 5345 Appendix
Standards evolve as a result of research and accident investigation. Major accidents have driven significant improvements to Ex standards and working practices:
Piper Alpha (1988) — North Sea, 167 fatalities. Led to major revisions of offshore safety management and inspection requirements.
Deepwater Horizon (2010) — Gulf of Mexico. Drilling rig explosion and sinking, massive oil spill. Reinforced requirements for well control and hazardous area management.
2.4 Equipment Certification
Ex equipment is certified by independent Certification Bodies (Notified Bodies under ATEX, ExCBs under IECEx) who verify that the manufacturer's design meets the relevant standards. Certification provides assurance of quality, safety, and suitability for the intended application.
The reasons for certification are:
Demonstrates product quality and safe function in a hazardous environment
Enhances market acceptability — inspires confidence in those who select, install, and maintain the equipment
Improves quality and safety control across the supply chain
ATEX Notified Bodies
A Notified Body is assessed and accredited by a national body (UKAS in the UK), then notified to the European Commission. Each has a unique NB number marked on certified equipment.
Notified Body
NB Number
Country
Baseefa Ltd (Bureau of Certified Safety)
1180
UK
SIRA Certification Service
0518
UK
ITS Testing and Certification
0359
UK
LCIE (Laboratoire Central)
0081
France
PTB (Physikalisch-Technische Bundesanstalt)
0102
Germany
CESI
0722
Italy
Certificate Number Formats
ATEX EC-Type Examination Certificate format:
Baseefa 04 ATEX 0273 X ↑ Notified Body ↑Year ↑Identifier ↑Serial ↑Suffix
IECEx Certificate of Conformity format:
IECEx BAS 06.0014 X ↑ Scheme ↑Body ↑Year.Serial ↑Suffix
⚠ Certificate Suffixes — Action Required
Suffix U — Component Certificate
The item is certified as a component only — not as complete equipment. It must be incorporated into a further certified assembly before installation in a hazardous area. Using a U-certified component as standalone equipment is non-compliant.
Suffix X — Special Conditions of Use
Special conditions of use apply to the equipment. These conditions are stated on the certificate itself — they may restrict ambient temperature, cable type, mounting orientation, or other installation parameters. Read the certificate. Verify compliance. If conditions are not met, the certification is invalid.
2.5 Equipment Nameplate Marking
All Ex equipment must display its certification marking on the nameplate. Reading this marking correctly and verifying it against the area classification is a core competency required for every CompEx unit.
2.5.1 Traditional Ex Marking (pre-IECEx)
Components of the traditional marking:
The symbol Ex (or EEx for equipment to EN 50000 standards)
The type of explosion protection (d, e, i, m, n, o, p, q)
The gas/apparatus group (IIA, IIB, IIC)
The temperature class, T-rating (T1–T6)
Example with ambient temperature range: EEx d IIB T6 -40°C < Tamb < +50°C
2.5.2 ATEX Marking
ATEX equipment adds the hexagon Ex symbol, the CE mark with notified body number, and the group/category information:
⑇ CE 1180 II 2 G Ex d IIB T4 Gb
Element
Meaning
⑇
Ex hexagon — ATEX Directive compliance
CE 1180
CE mark with Notified Body number (1180 = Baseefa)
II
Equipment Group II — surface industries (not mining)
2 G
Category 2, Gas — suitable for Zone 1 as minimum
Ex d
Flameproof enclosure — IEC 60079-1
IIB
Gas group — IIA and IIB atmospheres only, NOT IIC
T4
Temperature class — maximum surface temperature 135°C
Gb
Equipment Protection Level — Zone 1 and Zone 2 suitable
2.5.3 IECEx Marking
IECEx equipment to the latest IEC standards includes the EPL in the marking and omits the ATEX category/group prefix:
IECEx Marking Example
Meaning
Ex e II T5 Gb
Increased safety, Group II all subdivisions, T5, EPL Gb
Ex d IIB T4 Gb
Flameproof, IIB only, T4, EPL Gb (Zone 1+2)
Ex ia IIC T6 Ga
Intrinsically safe ia, IIC, T6, EPL Ga (Zone 0+1+2)
Ex d [ia Ga] IIC Gb
Flameproof enclosure (Gb) containing IS associated apparatus (ia Ga)
2.6 Equipment Protection Levels (EPLs)
EPLs were introduced in the latest editions of IEC 60079 standards. They use suffixes a, b, c corresponding to ATEX Categories 1, 2, 3, providing a clear indicator of where equipment can be safely used.
The three protection levels are Very High (a), High (b), and Enhanced (c).
Ga
Very High Protection
Not an ignition source in normal operation, expected faults, or rare faults. Safe with 2 simultaneous faults.
Cat 1 · Zone 0, 1, 2
Gb
High Protection
Not an ignition source in normal operation or expected faults. Safe with 1 fault.
Cat 2 · Zone 1, 2
Gc
Enhanced Protection
Not an ignition source in normal operation. May have additional protection for regular occurrences.
Cat 3 · Zone 2 only
Types of Protection, Zones, and EPLs — Complete Reference Table
Protection Type
Ex Marking
Zones of Use
ATEX Cat
IEC EPL
Intrinsic Safety
Ex ia
0, 1, 2
1
Ga
Encapsulation
Ex ma
0, 1, 2
1
Ga
Two independent Gb protection types
—
0, 1, 2
1
Ga
Flameproof
Ex d
1, 2
2
Gb
Increased Safety
Ex e
1, 2
2
Gb
Intrinsic Safety
Ex ib
1, 2
2
Gb
Encapsulation
Ex mb
1, 2
2
Gb
Oil Immersion
Ex o
1, 2
2
Gb
Pressurisation
Ex px, Ex py
1, 2
2
Gb
Powder Filling
Ex q
1, 2
2
Gb
Intrinsic Safety
Ex ic
2
3
Gc
Encapsulation
Ex mc
2
3
Gc
Non-sparking
Ex nA
2
3
Gc
Protected sparking
Ex nC
2
3
Gc
Restricted breathing
Ex nR
2
3
Gc
Pressurisation
Ex pz
2
3
Gc
2.7 ATEX and IEC Equipment Groups
Group
Application
Subdivision
Group I
Underground mining — firedamp (methane) and combustible dust
The traditional approach selects equipment EPL to match the zone. The risk assessment approach allows the team classifying the area to also specify an EPL based on the consequences of an explosion — unusually severe consequences may require a higher EPL than the zone alone would indicate; unusually low consequences may permit a lower EPL. When risk assessment EPLs have been determined, they appear on the area classification drawing alongside the zone, gas group, and T-class.
Unit 2 Knowledge Check — 10 Questions
CompEx-style questions covering the full unit content.
Q1Unit {num}
Which ATEX directive governs the health and safety obligations of employers in potentially explosive atmospheres?
ATEX 137 (Workplace Directive 1999/92/EC) governs employer obligations including risk assessment, explosion protection documents, zone classification, and safe working procedures. ATEX 95 (Equipment Directive) governs the equipment itself. In the UK, ATEX 137 is implemented through DSEAR.Ref: ATEX Directive 1999/92/EC
Q2Unit {num}
An ATEX certificate number reads "Baseefa 04 ATEX 0273 X". What does the X mean?
The X suffix means special conditions of use apply. These conditions are stated on the certificate itself. They may restrict ambient temperature range, cable type, mounting position, or other installation parameters. The installer must read the certificate and verify that all special conditions are satisfied before the equipment is installed.Ref: IEC 60079-0 / ATEX — Certificate Suffix X
Q3Unit {num}
Which IEC 60079 standard covers the design, selection and erection of electrical installations in hazardous areas?
IEC 60079-14 covers electrical installation design, selection and erection — cable selection, gland requirements, earthing, IS system design, and installation practice. IEC 60079-10 covers area classification. IEC 60079-17 covers inspection and maintenance. IEC 60079-19 covers repair and overhaul.Ref: IEC 60079-14
Q4Unit {num}
Equipment marked "Ex ia IIC T6 Ga" can be installed in which zones?
EPL Ga (very high protection — safe with two independent faults) is the highest EPL for gas atmospheres. Equipment with EPL Ga is suitable for Zone 0, Zone 1, and Zone 2. Higher EPL equipment can always be used in less hazardous zones.Ref: IEC 60079-0 — EPL Ga Definition
Q5Unit {num}
What does "Category 3 G" mean in an ATEX marking?
Category 3 G means Category 3, Gas application. Category 3 corresponds to EPL Gc — suitable for Zone 2 only. The G suffix indicates it is for gas atmospheres (as opposed to D for dust). Category 1 = Zone 0 (EPL Ga). Category 2 = Zone 1 (EPL Gb).Ref: ATEX Directive 94/9/EC — Category System
Q6Unit {num}
A piece of equipment is certified "Ex d [ia Ga] IIC Gb". What does the square bracket notation mean?
The square bracket notation [ia Ga] indicates that the enclosure contains IS associated apparatus. The flameproof enclosure body is EPL Gb (Zone 1 suitable). The IS output from the apparatus within provides EPL Ga protection to the field device. The IIC refers to the gas group of both the enclosure and the IS circuit.Ref: IEC 60079 — Hybrid Protection Marking
Q7Unit {num}
Which Notified Body number is associated with Baseefa Ltd in the UK?
Baseefa Ltd (Bureau of Certified Safety) has Notified Body number 1180. SIRA is 0518, ITS is 0359, PTB (Germany) is 0102. The NB number appears on the CE mark portion of ATEX equipment markings (e.g. CE 1180).Ref: ATEX Directive — Notified Bodies
Q8Unit {num}
Equipment has an "IECEx" certificate but no ATEX certificate. Can it be installed in the EU/UK?
IECEx is an international scheme accepted in 50+ countries, but for the EU, ATEX certification is still required. Equipment sold in the EU must comply with the ATEX Equipment Directive. IECEx and ATEX can coexist on the same piece of equipment. Post-Brexit UK uses UKEX (the UK implementation of ATEX requirements).Ref: ATEX vs IECEx Certification
Q9Unit {num}
Temperature class T5 is marked on equipment. What is the maximum surface temperature this equipment will reach?
T5 allows a maximum surface temperature of 100°C. T4 = 135°C, T6 = 85°C. T5 (100°C) is required where the gas ignition temperature falls between 100°C and 135°C — for example, carbon disulphide (95°C) requires T6, but some materials with ignition temperatures around 105-120°C would need T5 minimum.Ref: IEC 60079-0 — Temperature Classification
Q10Unit {num}
An area is classified Zone 1, IIB, T4. Equipment marked "Ex e IIC T3 Gb" is available. Why is T3 NOT acceptable?
T4 requires that equipment surface temperature stays below 135°C. T3 allows the surface to reach 200°C. Installing T3-rated equipment in a T4 area means the surface could reach 200°C — which exceeds the 135°C T4 limit and could ignite gases with ignition temperatures between 135°C and 200°C. The T-class of the equipment must be equal to or more stringent (higher number) than the area requirement.Ref: IEC 60079-0 — T-Rating Selection