This document provides information on IEC protection techniques for hazardous areas and areas with combustible dust, including definitions of IEC zones and IP ratings. It also includes charts comparing IEC and NEC area classifications, zone definitions, and guidelines for using equipment certified for different standards.

1. IEC, NEC, CEC, ATEX Hazardous Location Guide
EGS Electrical Group
9377 W. Higgins Road
Rosemont, IL 60018
1.800.621.1506
www.egseg.com
Canada
888.765.2226
Mexico
52.55.5809.5070
Asia/Pacific
65.6891.7600
China
86.21.5426.0668
Middle East
971.4.8838.831
Europe
33.1.4817.8502
South America
Nutsteel Indústria Metalúrgica Ltda.
São Paulo/SP – Brazil
55.11.2122.5777
Macaé/RJ – Brazil
55.22.2770.4686
Camaçari/BA – Brazil
55.71.3623.2028
CHART 14 — IEC Protection Techniques for Hazardous Areas
FLAMEPROOF “d”
• ZONE 1
• Contain internal explosion
• Control external temperature of enclosure
• Similar to NEC®
explosionproof
• Usually cast enclosure
• Typical use in lighting and motor starters
REQUIREMENTS:
• Internal explosion cannot be transmitted outside enclosure
• External temperature of enclosure below ignition temperature of surrounding gases
• Cable fittings must have 5 threads engaged
• Internal and external ground screw
Increased safety “e”
• ZONE 1
• High impact resistant enclosures—FRP, GRP, sheet steel/aluminum, stainless steel
• Enclosure will not hold static charge
• Maintain minimum of IP 54 ingress protection
• Apparatus non arcing/sparking
• Typical use in terminal enclosures
REQUIREMENTS:
• Use IEC approved non-loosening screw type in IEC approved enclosures
• Control internal and external temperature
FLAMEPROOF PLUS INCREASED SAFETY “de”
“d”
“e”
• ZONE 1
• Location of arcing has “d” protection (flameproof)
• Connection terminals have “e” protection (increased safety)
• Typical use in switches, lighting, controls, plugs and receptacles/sockets
Items such as power outlets, switches, some lighting, etc., cannot be protected by “e” mode only. In this case “d” and “e” are combined.
REQUIREMENTS:
• Area where arc can be produced is “d” or flameproof in a restricted volume enclosure - often contact blocks and switches
• Area with connection terminals is “e” or increased safety
• Controls internal and external temperatures
INTRINSIC SAFETY “ia” - “ib” - “ic”
• ia ZONE 0
• ib ZONE 1
• ic ZONE 2
• Incapable of releasing enough energy to cause an explosion
• Typical use in communication equipment
REQUIREMENTS:
• Install in safe areas (non IS), or in an approved “d” enclosure
• Energy limiting barriers
• Transmits signal from hazardous area (IS)
• Prevents energy release
• Ensure isolation of circuits between IS and non IS areas
Encapsulation “m”
• ZONE 1
• Epoxy or other resin to totally seal arcing and sparking devices
• Typical use in lighting controls and sealed switches
REQUIREMENTS:
• Arcing and sparking devices totally immersed by epoxy or other resin
• IEC approved non-loosening connectors
• Controls internal and external temperatures
NON-SPARKING “n”
• ZONE 2
• Enclosure restricts ingress of hazardous gases
• nA=non sparking construction
• nR=restricted breathing
• nC=hermetically sealed, non incendive
• Typical use in lighting fixtures
REQUIREMENTS:
• Equipment has no normally arcing parts
• Thermal effects incapable of ignition
• nA=non sparking
• nR=restricted breathing
• nC=hermetically sealed non incendive
OIL IMMERSION “o”
• ZONE 1
• Oil totally seals arcing and sparking devices
• Typical use in hazardous rated transformers and switches
REQUIREMENTS:
• Arcing and sparking devices totally immersed by oil
• IEC approved non-loosening connectors
• Controls internal and external temperatures
PRESSURIZED APPARATUS “p”
• ZONE 1
• Expels ignitable vapor/gas
• Maintains positive enclosure pressure
REQUIREMENTS:
• Install in safe areas (non IS), or in an approved “d” enclosure
• Energy limiting barriers
• Transmits signal from hazardous area (IS)
• Prevents energy release
• Ensure isolation of circuits between IS and non IS areas
POWDER FILLING “q”
• ZONE 1
• Finely ground powder to totally seal arcing and sparking devices
• Typical use in lighting, controls and sealed switches
REQUIREMENTS:
• Arcing and sparking devices totally immersed by finely ground powder
• IEC approved non-loosening connectors
• Controls internal and external temperatures
CHART 15 — IEC Protection Techniques for Areas With Combustible Dust
INTRINSIC SAFETY “iD”
• iaD for use in ZONE 20, 21, 22
• iaD for use in ZONE 21, 22
• (Ex ibD) associated electrical apparatus - installation in the safe areas
• Incapable of releasing enough energy to cause an explosion
• Typical use in communication equipment
REQUIREMENTS:
• Install in safe areas (non IS), or in an approved “d” enclosure
• Energy limiting barriers
• Transmits signal from hazardous area (IS)
• Prevents energy release
• Ensure isolation of circuits between IS and non IS areas
ENCAPSULATION “mD”
• maD for use in ZONE 20, 21, 22
• mbD for use in ZONE 21, 22
• Epoxy or other resin to totally seal arcing and sparking devices
• Typical use in lighting, controls and sealed switches
REQUIREMENTS:
• Arcing and sparking devices totally immersed by epoxy or other resin
• IEC approved non-loosening connectors
• Controls internal and external temperatures
PRESSURIZATION “pD”
• ZONE 21, 22
• Expels ignitable vapor/gas
• Maintains positive enclosure pressure
REQUIREMENTS:
• Install in safe areas (non IS), or in an approved “d” enclosure
• Energy limiting barriers
• Transmits signal from hazardous area (IS)
• Prevents energy release
• Ensure isolation of circuits between IS and non IS areas
PROTECTION BY ENCLOSURES “tD”
• tD A21 Procedure A for ZONE 21
• tD B21 Procedure B for ZONE 21
• High impact resistant enclosures—FRP, GRP, sheet steel/aluminum, stainless steel
• Enclosure will not hold static charge
• Maintain minimum of IP 54 ingress protection
• Apparatus non arcing/sparking
• Typical use in terminal enclosures
REQUIREMENTS:
• Use IEC approved non-loosening type enclosures
• Control internal and external temperature
CHART 1 — What is aN IEC zone?
The IEC has defined 3 areas of hazardous gas or vapor release as follows:
ZONE 0 ZONE 1 ZONE 2
Explosive Atmosphere Is Continuously Present Explosive Atmosphere Is Often Present Explosive Atmosphere May Accidentally Be Present
1000 hours/year 10-1000 hours/year 0.1 - 10 hours/year
Zone in which an explosive mixture of gas, vapor or mist
is continuously present.
Zone in which an explosive mixture of gas, vapor or mist
is likely to occur during normal operation.
Zone in which an explosive mixture is not likely to occur
in normal operation, and if it occurs will only exist for a
short time (leaks or maintenance).
The IEC has defined 3 areas of hazardous/combustable dusts as follows:
ZONE 20 ZONE 21 ZONE 22
Explosive Atmosphere Is Continuously Present Explosive Atmosphere Is Often Present Explosive Atmosphere May Accidentally Be Present
1000 hours/year 10-1000 hours/year 0.1 - 10 hours/year
Zone in which an explosive mixture of dust is
continuously present.
Zone in which an explosive mixture of dust is likely to
occur during normal operation.
Zone in which an explosive mixture of dust is not likely
to occur in normal operation, and if it occurs will only
exist for a short time (leaks or maintenance).
CHART 12 — Understanding the Ingress Protection System
IP
The IEC IP classification system designates the degree of protection provided by an enclosure against impact and/or water or dust penetration
(ingress). It has two numbers; first—protection against solid objects, second protection against liquid.
EXAMPLE: IP 54
1st
Figure: protection against solid bodies 2nd
Figure: protection against liquids
IP TESTS IP TESTS
0 No protection 0 No protection
1
Protected against solid bodies larger than 50mm
(e.g. accidental contact with the hand)
1
Protected against vertically-falling drops of water
(condensation)
2 Protected against solid bodies larger than 12.5mm
(e.g. finger of the hand)
2
Protected against drops of water falling at up to 15˚
from the vertical
3 Protected against solid bodies larger than 2.5mm
(tools, wires)
3
Protected against drops of rainwater at up to 60˚ from
the vertical
4 Protection against solid bodies larger than 1mm
(fine tools, small wires)
4
Protected against projections of water from all
directions
5 Protected against dust (no harmful deposit) 5 Protected against jets of water from all directions
6 Completely protected against dust 6
Completely protected against jets of water of similar
force to heavy seas
7 Protected against the effects of temporary immersion
8 Protected against effects of prolonged immersion under
specified conditions
Glossary
AEx
Symbol designates equipment built to NEC®
standards for use in NEC®
Zone designated areas.
Such products are not suitable for use in ATEX or IEC Ex applications.
ATEX
ATmosphères EXplosibles – Organizations in the EU where ‘explosion risk’ exists, must use the guidelines for protecting the employees of the
companies. Manufacturers who apply its provisions and affix the CE marking are able to sell their equipment anywhere in EU without any further
requirements being applied with respect to the risks covered being applied.
CEC Canadian Electric Code.
CENELEC
European Committee for Electrical Standardization. CENELEC develops electrotechnical standards that are adopted as Euronorms by the EU for electrical
and electronic goods and services. It is comprised of a group of 31 European countries and 11 affiliated countries that have CENELEC standards based on
the parallel working IEC/CENELEC.
Class I
Term used in NEC®
to describe locations in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce
explosive or ignitable mixtures.
Class II Term used in NEC®
to describe locations that are hazardous because of the presence of combustible dust.
Class III
Term used in NEC®
to describe locations that are hazardous because of the presence of easily ignitable fibers or flyings but in which such fibers or
flyings are not likely to be in suspension in the air.
CSA
Canadian Standard Association - Provider of product testing certification services for US, Canada and countries worldwide,
for electrical, plumbing, gas mechanical products.
Division 1 Term used in NEC®
to describe the condition in which the hazard can be present during normal conditions.
Division 2 Term used in NEC®
to describe the condition in which the hazard is present only under abnormal conditions.
CHART 13 — Approximate Conversion of NEMA Enclosure Type Ratings to IEC 60529 Enclosure Classification Designations (IP)
(Cannot be Used to Convert IEC classification Designations to NEMA Type Ratings or vice versa)
IP First
Character
NEMA Enclosure Type
IP Second
Character
1 2 3, 3X, 3S, 3SX 3R. 3RX 4, 4X 5 6 6P 12, 12K, 13
IP0_ IP_0
IP1_ IP_1
IP2_ IP_2
IP3_ IP_3
IP4_ IP_4
IP5_ IP_5
IP6_ IP_6
IP_7
IP_8
A B A B A B A B A B A B A B A B A B
A = A shaded block in the “A” column indicates that the NEMA Enclosure Type exceeds the requirements for the respective IEC 60529 IP First Character Designation.
The IP First Character Designation is the protection against access to hazardous parts and solid foreign objects.
B = A shaded block in the “B” column indicates that the NEMA Enclosure Type exceeds the requirements for the respective IEC 60529 IP Second Character Designation.
The IP Second Character Designation is the protection against the ingress of water.
Example of Table Use: An IEC IP 45 Enclosure Rating is specified. What NEMA Type Enclosures meet and exceed the IP 45 rating?
Referencing the first character, 4, in the IP rating and the row designated “IP4_” in the left most column in the table; the blocks in Column “A” for NEMA Types 3, 3X, 3S, 3SX,
3R, 3RX 4, 4X, 5, 6, 6P, 12, 12K and 13 are shaded. These NEMA ratings meet and exceed the IEC protection requirements against access to hazardous parts and solid foreign
objects.
CHART 3 — AREA CLASSIFICATION—IEC vs NEC®
/CEC (CLASS/DIVISION/GROUP)
Inflammable Material IEC/CENELEC NEC®
/CEC
Gases and Vapors Protection Zone Group
Sub-
division
Class Division Group
Acetylene d and/or e 1 or 2 II C I 1 or 2 A
Hydrogen d and/or e 1 or 2 II B + H2
I 1 or 2 B
Propylene oxide, Ethyl oxide, Butadiene d and/or e 1 or 2 II B I 1 or 2 B
Cyclopropane, Ethyl ether, Ethylene d and/or e 1 or 2 II B I 1 or 2 C
Acetone, Benzene, Butane, Propane, Hexane,
Paint solvents, Natural gas
d and/or e 1 or 2 II A I 1 or 2 D
CHART 8 — Simplified…Where to Use
Equipment listed/marked for: Use—as Noted
NEC®
Class I, Div. 1 OK for use in NEC®
Class I, Zone 1 and 2
NEC®
Class I, Div. 2 OK for use in NEC®
Class I, Zone 2
NEC®
Class I, Zone 1 NOT OK for use in NEC®
Class I, Div. 1
NEC®
Class I, Zone 2 OK for use in NEC®
Class I, Div. 2
NEC®
AEx OK for NEC®
Zone 0, 1, 2 as marked
NEC®
AEx NOT suitable for NEC®
Class I, Div. 1
NEC®
AEx OK for use in NEC®
Class I, Div. 2
IEC Zone 1 NOT suitable for any NEC®
area
IEC Zone 2 NOT suitable for any NEC®
area
IEC Ex or CENELEC EEx NOT suitable for any NEC®
area
CHART 7 — Examples of NEC®
/CEC CLASS I, DIVISION 1 and 2 SITUATIONS
CLASS I, DIVISION 1 CLASS I, DIVISION 1 AND 2 NON CLASSIFIED
EXAMPLE 1
CONDITIONS:
 Class I, Division 1 hazard exists during normal operation
conditions
• Open air mixing tank
• Products stored in work area
 Area classified based on properties of vapors present
 Electrical equipment must use approved Div. 1 NEC®
protection techniques and wiring methods
EXAMPLE 2
CONDITIONS:
 Division 2 area can exist where vapors are normally in closed system or containers
 Division 1 and 2 areas separated by barrier or space
(transition zone)
• Hazardous areas properly documented
• Div. 2 must use approved NEC®
wiring methods and products
 Stored products outside Div. 1 work area
 Non hazardous area
EXAMPLE 3
CONDITIONS:
 Closed tank and piping confines Div. 1
 Yellow area qualifies as Div. 2
 Stored products not present
 Purged/pressurized control room qualifies as “non hazardous” is sealed off from
Div. 2 area
 Electrical equipment in Div. 2 must use approved Div. 2 protection techniques
and products
CHART 6 — Examples of IEC zone classification SITUATIONS
ZONE 0 ZONE 1 ZONE 2 NON HAZARDOUS ZONE
EXAMPLE 1
CONDITIONS:
 All manual ventilation
 Zone 0 area
 Zone 1 area
 Non hazardous area
• Open air mixing tank
• No mechanical ventilation
• Products stored in work area
EXAMPLE 2
CONDITIONS:
 Hood over tank
 Zone 0 area
 Zone 1 area
 Zone 2 area
 Non hazardous area
 Mechanical ventilation
 Stored products separated from work area
EXAMPLE 3
CONDITIONS:
 Tank closed
 Mechanical ventilation
 Zone 0
 Zone 2
 Non hazardous area
• Operations control outside zones
CHART 5 — Groups and subgroups classification — IEC
Groups Subgroups Typical Substance Application/Definition
Group I I Methane
Electrical Equipment for use in mines
susceptible to firedamp
(Not applicable to ATX Series Products)
Group II
IIA Propane
Electrical equipment for use in places
with an explosive gas atmosphere
IIB Ethylene
IIC Hydrogen
Group III (new)
IIIA Combustible flyings
Electrical equipment for use in places
with an explosive dust atmosphere
IIIB Non-conductive dust
IIIC Conductive dust
CHART 2 — COMPARING IEC ZONES AND NEC®
/CEC DIVISIONS
ZONE 0 / zONE 20 Zone 1 / zONE 21 ZONE 2 / zONE 22
Division 1 Division 2
CHART 4 — IEC vs NEC®
/CEC TEMPERATURE CLASSIFICATION COMPARISON
Max. Surface
Temp. (°C)
85 100 120 135 160 165 180 200 215 230 260 280 300 450
IEC Classification T6 T5 T4 T3 T2 T1
North American
Classification
T6 T5 T4A T4 T3C T3B T3A T3 T2D T2C T2B T2A T2 T1
CHART 9 — Equipment MARKINGS
UNDERSTANDING IEC MARKINGS †
Ex de II C T6 Gb ‡
Ga for zone 0
Gb for zone 1
Gc for zone 2
Temperature Class T6 =
Max 85˚°C Surface
TemperatureGas Subdivision
Group-C = Acetelyne
Group II = Surface Equipment
Group I = Mines
Type of Protection d = “flameproof”
Type of Protection e = “increased safety”
Explosion Protected Meets IEC Standards
AEx = Equipment conforms to NEC®
† Alternate marking: Ex deb IIC T6.
‡ This only applies to IEC Standards only. See “Chart 10 — Understanding IEC Equipment Protection Level Requirements” below.
UNDERSTANDING NEC®
/CEC MARKINGS
Class I Division 1 Group A
A = Acetylene
I = Gas and Vapors
1 = Hazard normally present B = Hydrogen
II = Dust
2 = Hazard abnormally present C = Ethylene
III = Fibers and Flyings
D = Gasoline
E = Electrically Conductive Dust
F = Fuel Dust
G = Grain Dust
UNDERSTANDING ATEX MARKINGS (Directive 94/9/EC) *
• • • II 1 G
CE Marking
Symbol
ID No. of Notified
Body of the QA
System
EU Explosive
Atmospheres
Symbol
Surface
(non-mining)
Equipment
Equipment
Category
Type of Flammable
Substance
Ex ia IIC T4 Ga
Ex: Conformity to IEC and ATEX Hazardous area
standards; Suitability for use in IEC and
ATEX hazardous locations
Protection Method
(intrinsic safety)
Gas Group
(acetylene
hydrogen)
Temperature
Class
Equipment Level
Protection:
Ga for zone 0
Gb for zone 1
Gc for zone 2
* See “Chart 11 — ATEX Equipment Category” below.
CHART 11 — ATEX Equipment Category
The ATEX directive adds “The Equipment Category” to the marking which indicates the level of protection which correlates back to the manufacturers quality assurance
requirements as shown on this chart.
Equipment Group
Equipment Category and
Level of Protection
Presence or Duration of
Explosive Atmosphere
Flammable Substances Correlation with
Hazardous Areas
I - Mines
M1 - Very high level of
protection
Continuos Presence Methane, Combustible Dust
M2 - High level of protection
II - Surface
1 - Very high level of protection Continuous Presence
G - Gas, Vapors
D - Dust
Zone 0 (Gas etc.)
Zone 20 (Dust)
2 - High level of protection Likely to Occur
Zone 1 (Gas etc.)
Zone 21 (Dust)
3 - Normal level of protection Unlikely to Occur
Zone 2 (Gas etc.)
Zone 22 (Dust)
Glossary
Ex Designation for hazardous location equipment complying to IEC and ATEX standards.
Flameproof An IEC or European term using “containment” protection. Similar to, but not exactly the same as US “explosionproof”.
Group
Class I: Term used in NEC®
to define a collection of gases with similar physical properties such as maximum explosion pressure.
Class II: Term used in NEC®
to define a collection of hazardous dusts with similar physical characteristics such as ignition temperature as well as
attributes such as blanketing effect on equipment.
Class III: There are no Group listings.
Hazardous Location
Exists when a manufacturing, storage or handling process provides a fuel, consisting of a flammable gas, combustible dust, combustible flying or
fiber, or some combination of these three elements; and these flammable components can be mixed with enough oxygen from the ambient air to form
an explosive atmosphere between the Lower Explosive or Flammable Limit (LEL/LFL) and the Upper Explosive or Flammable Limit (UEL/UFL).
IEC International Electrotechnical Commission - International Standards and conformity assessment for all electrical, electronic and related technologies.
IECEx
International Electrotechnical Commission Explosive Atmospheres - An IECEx Scheme provides a means for manufacturers of EX equipment to obtain
Ex certificates of conformity that will be accepted at national level in all participating countries.
NEC®
National Electric Code - Governs the installation of electrical conductors, equipment, and raceways.
Subdivision Zone system grouping of various gas/vapors roughly equal to NEC®
“Group”.
UL Underwriters Laboratories - A US testing and certification organization.
Zone
Defines conditions under which explosive gases are present in an area.
Zones are similar to divisions, but are generally based on length of time hazardous material may be present.
Chart 10 — UNDERSTANDING IEC Equipment Protection Level Requirements
Protection
Afforded
Equipment Protection
Level (EPL)
Group Performance of Protection Conditions of Operation
Very high
Ma Group I
Requires two independent means of protection or
remains safe when two different malfunctions occur
Equipment used in explosive atmosphere
Ga Group II Used in Zones 0,1 and 2
Da Group III Used in zones 20, 21, and 22
High
Mb Group I Good for use in normal and severe operating conditions Equipment de-energized in explosive atmosphere
Gb Group II Good for use in normal operation or where
equipment malfunctions are considered
Used in Zones 1 and 2
Db Group III Used in Zones 21, and 22
Enhanced
Gc Group II
Good for normal operation
Used in Zones 2
Dc Group III Used in zones 22