This document provides definitions and classifications for hazardous area equipment certification. It includes: 1) Definitions for gas and dust zone classifications, IP and IK protection codes, ATEX equipment categories, types of explosion protection, conformity assessment modules, and temperature classes. 2) Charts listing gas and dust groups, typical zone suitability, radio frequency power thresholds, and cable gland selection guidance. 3) Abbreviated descriptions of common NEMA, UL, and CSA enclosure types and their approximate IEC/IP classifications.

1. II 2 G Ex d IIC T4
Zoning Definitions
Zones
Gas Dust
A place in which an explosive
atmosphere is continually present
A place in which an explosive
atmosphere is likely to occur in normal
operation occasionally
A place in which an explosive atmosphere
is not likely to occur in normal operation,
but if it does only occurs for short periods
Definitions
IP Code
1st Numerical 2nd Numerical
Protection against Solid Bodies Protection against Liquid
0 No protection 0 No protection
1 Objects > 50mm 1 Vertically dripping water
2 Objects > 12mm 2 Drops of liquid (75° to 90°)
3 Objects > 2.5mm 3 Sprayed water
4 Objects > 1mm 4 Splashed water
5 Dust-protected 5 Water jets
6 Dust-tight 6 Heavy seas
7 Effects of immersion
8 Indefinite immersion
Categories
ATEX
Cat.
1G Equip. suitable for zone 0
1D Equip. suitable for zone 20
2G Equip. suitable for zone 1
2D Equip. suitable for zone 21
3G Equip. suitable for zone 2
3D Equip. suitable for zone 22
Typical Zone
Suitability
Dusts
Zone
20 Requires 1D equipment IP6X
21 Requires 1D or 2D equipment IP6X
22 Requires 3D, 2D or 1D equipment IP5X*
* Must be IP6X if dust is electrically conductive
ATEX Category
IP
Rating
Types of Protection
Temperature
GAS
Type of Protection
General Requirements – EN 60079-0
Intrinsic Safety Ex ia & ib EN 60079-11
Increased Safety Ex e EN 60079-7
Flameproof Ex d EN 60079-1
Pressurisation Ex p EN 60079-2
Powder Filling Ex q EN 60079-5
Encapsulation Ex ma &mb EN 60079-18
Oil Immersion Ex o EN 60079-6
Type n Ex n EN 60079-15
Standard
Non-electrical Equipment (concepts)
EN 13463-1 Basic methods & requirements
EN 13463-2 Flow restricting enclosure fr
EN 13463-3 Flame-proof enclosure d
EN 13463-5 Constructional safety c
EN 13463-6 Control of ignition sources b
EN 13463-7 Pressurisation p
EN 13463-8 Liquid immersion k
Complies with
European
Directive
EC Mark
XXXX
Notified Body
Number
Equipment
Group
Equipment
Category
Gas
Explosion
Protection
Type of
Protection Gas Group*
A, B or C
*If omitted suitable
for all gas groups
Temperature
Class
(T1-T6)
Conformity Assessment ‘Quality Modules’
Design Phase
EC-Type Examination
Internal Control of Production
Unit Verification
Production Phase
Production Quality Assurance
Product Quality Assurance
Product Verification
Conformity to Type
Internal Control of Production
Unit Verification
Module Annex
*1 *2
Protective
System
B III ✔ ✔ ✔ ✔ ✔
A VIII ✔*4 ✔*4 ✔
G IX O O O O O O O O
D IV Y Y Y
E VII Y Y
F V Y Y Y
C VI Y Y
A VIII ✔ ✔ ✔
G IX O O O O O O O O
Marking for
Gas Hazards
T-Class
T1 450
T2 300
T3 200
T4 135
T5 100
T6 85
Max surface
temp in °C
Groups
Gas Groups
I Electrical equipment intended for use in mines susceptible
to firedamp
II Electrical equipment intended for use in places with an
explosive gas atmosphere other than mines susceptible to
firedamp
III Electrical equipment intended for use in places with an
explosive dust atmosphere other than mines susceptible to
firedamp*
IIA Propane
IIB Ethylene
IIC Hydrogen/Acetylene
Dust Groups*
IIIA Combustible Flyings
IIIB Non-conductive Dust
IIIC Conductive DustType n EN60079-15
Enclosed break device nC
Non-incendive component nC
Hermetically sealed device nC
Sealed device nC
Encapsulated device nC
Energy limited apparatus & circuits nL
Restricted breathing enclosure nR
Non sparking nA
III 2 D Ex tD A21 IP66 T80°C
Complies with
European
Directive
EC Mark
XXXX
Notified Body
Number
Equipment
Group
Equipment
Category
Dust
Explosion
Protection
Type of
Protection
Marking for
Dust or Flyings
and Fibres
Hazards
Conformity Assessment ‘Quality Modules’ Table
* Notes:
1 “Global Approach” OJEC No.L220, 1993
2 ATEX Directive 94/9/EC
3 Suffix (E) refers to electrical equipment and
internal combustion engines
Suffix (N) refers to non-electrical equipment
4 Technical Files to be deposited with a notified
body
KEY
✔ = mandatory unless Unit Verification is used
O = optional as an alternative to other modules
Y = one of two production phase modules for
the equipment category to be chosen by the
manufacturer
Equipment Category *3
M1 M2 M2 1 2 2 3
(E) (N) (E) (N)
EN 60079-10 EN 61241-10
0 20
1 21
2 22
Equipment Threshold power Thermal Initiation Time
for (W) (averaging period)
(µs)
START
Is area zoned?
Zone 1?
Is equipment
Ex d concept?
Is equipment
Ex i concept?
Use non-certified
cable glands
*refer to note 1
Refer to Ex d
cable selector
chart
Gland type
Ex e concept
Ex n* or N
concept
Zone 2
Use non-certified
cable glands
*refer to note 2
Use certified
cable glands
Brass
Yes
Yes No
Yes
Yes No
Yes No
No
Yes No
Yes
No No No
Plastic
Use a suitable
flameproof cable
gland with a
sealing ring.
(Gland with
elastomeric
seals)
Is the area of
installation of
Zone 1?
Is the
volume of
enclosure
greater than
2 dm3?
Use a barrier
gland
Does the
hazardous
gas require IIC
apparatus?
Yes
Ex e concept
*refer to note 3
Does this
enclosure
contain an
internal source
of ignition?
Cable Gland Selection
Note 1: Non certified cable glands
may be used provided that they
maintain the minimum IP rating on
the certified equipment of IP54 for
outdoors and IP20 for indoor
equipment.
Note 2: Non certified cable glands
may be used provided they meet
the requirements of EN60079-0 and
EN60079-7 or EN60079-15.
Note 3: Internal sources of ignition
include sparks or equipment
temperatures occurring in normal
operation which can cause ignition.
An enclosure containing terminals
only or an indirect entry enclosure is
considered not to constitute an
internal source of ignition.
Radio Frequency Sources
The threshold power of radio frequency (10 kHz to 300 GHz) for continuous transmissions and for pulsed
transmissions whose pulse durations exceed the thermal initiation time shall not exceed the values shown in Table 4.
Programmable or software control intended for setting by the user shall not be permitted.
For pulsed radar and other transmissions where the pulses are short compared with the thermal initiation time, the
threshold energy values Zth shall not exceed those given in Table 5.
ATEX Certification Definitions
Table 4 from IEC 60079-0
Radio Frequency Power Thresholds
Group I 6.0 200
Group IIA 6.0 100
Group IIB 3.5 80
Group IIC 2.0 20
Group III 6.0 200
Equipment Threshold Energy Zth
for (µJ)
Table 5 from IEC 60079-0
Radio-frequency Energy Thresholds
Group I 1500
Group IIA 950
Group IIB 250
Group IIC 50
Group III 1500
Note: The information in this wall chart is for guidance only. For detailed information see relevant Directives and Regulations.
DUST
Type of Protection
General Requirements – EN 61241-0:2006
Protection by Enclosures tD EN 61241-1:2004
Protection pD EN 61241-4:2006
Intrinsic Safety iD EN 61241-11:2006
Encapsulation mD EN 61241-18:2004
Standard
ATEX
Code
ATEX
Code
Ingress protection
and max. surface
temperature
*Taken from the new IEC60079-0 2007
Other Useful Standards
US Enclosure Ratings NEMA 7 to 10 Hazardous Area Enclosures
Simple Apparatus
Assessment of inadvertent ignition of flammable atmospheres
by radio frequency radiation (guide)
Explosive atmospheres - Explosion prevention and protection.
Part 1, Basic concepts & methodology for surface industry
Explosive atmospheres - Explosion prevention and protection.
Part 2, Basic concepts & methodology for mining
Classification of hazardous areas
Electrical installations in hazardous areas (other than mines)
Electrical installations inspection and maintenance
Equipment repair, overhaul and reclamation
Protection of equipment and transmission systems using
optical radiation
BS6656
EN1127-1
EN1127-2
EN60079-10
EN60079-14
EN60079-17
EN60079-19
EN60079-28
NEMA, UL
& CSA
type rating
Approximate
IEC/IP
classification
Abbreviated Protection Description
1 IP20
2 IP22
3 IP55
3R IP24
4 IP66
4X IP66
6 IP67
Indoor, from contact with contents
Indoor, limited, falling dirt and water
Outdoor, from rain, sleet, windblown dust & ice damage
Outdoor, from rain, sleet & ice damage
Indoor & outdoor, from windblown dust, rain, splashing
& hose directed water & ice damage
Indoor & outdoor, from corrosion, windblown dust, rain,
splashing & hose directed water & ice damage
Indoor & outdoor, from hose directed water, water entry
during submersion & ice damage
Mechanical Impacts (UK) Code EN50102
IK Code IK00 IK01 IK02 IK03 IK04 IK05 IK06 IK07 IK08 IK09 IK10
Impact
Energy * 0.14 0.2 0.35 0.5 0.7 1 2 5 10 20
(Joules)
5V in
Passive components
Well defined sources of
stored energy considered
in safety analysis
Sources of generated energy not
more than *1.5V, 100mA & 25mW
NOT
piezoelectric crystal
protected components
voltage or current enhancement
* Note: North America still
uses 1.2V and 20 microjoules