A GUIDE TO HAZARDOUS
LOCATIONS
Markings and Device Protection
Martin Denly BPE Design and Support Ltd
© Copyright BPE Design and Support Ltd 2014
A GUIDE TO HAZARDOUS LOCATIONS
1 Index
1
Index ....................................................................................................................1
2
Abbreviations .........................................................................................................1
3
Introduction ..........................................................................................................2
4
Equipment Choice ..................................................................................................2
5
Area Classification ..................................................................................................3
6
Equipment Protection Level (EPL) ............................................................................3
7
Markings ...............................................................................................................4
7.1
EU Markings ....................................................................................................4
7.2
IEC and Canada (CEC Sect.18) ..........................................................................5
7.3
US (under NEC 500) and Canada (under CEC Annex J) ........................................6
7.4
US (Under NEC 505) ........................................................................................6
8
Principals of Protection ...........................................................................................6
8.1
NO SPARKS OR HOT SURFACES ..............................................................................6
8.2
CONTAIN THE EXPLOSION AND LIMIT THE FLAME ........................................................7
8.3
LIMIT THE ENERGY AND SURFACE TEMPERATURE .........................................................7
8.4
EXCLUDE THE FLAMMABLE GAS ...............................................................................8
9
Temperature Classes ..............................................................................................9
10
Apparatus Grouping .......................................................................................... 10
11
Ingress Protection ............................................................................................. 10
2 Abbreviations
ATEX
CAN
CEC
CENELEC
EU
IEC
I.S.
NFPA
NEC
US
Atmosphère Explosible
Canada
Canadian Electrical Code (CSA C22.1)
European Committee for Electrotechnical Standardization
European Union
International Electrotechnical Commission
Intrinsic Safety
National Fire Protection Association (US)
National Electrical Code (US)
United States of America
Page 1
3 Introduction
This document is intended as a quick guide as to the markings and choices of device
protection within a Hazardous Area. It should not be used to define or understand the
nature of a Hazardous Area. Obviously standards referred to may be updated from time to
time.
4 Equipment Choice
The choice of equipment is dependent upon the location of the site. For example US sites
may use either NEC500 or NEC 505 or a combination of both. European suppliers to the US
market generally comply with NEC505 and often using the equivalent EU/IEC (ATEX)
standard request acceptance of this by the sites safety representative or fire officer.
For Zone 0 applications (EU and IEC definition) only Intrinsically Safe (Ex i[a]) and
Encapsulated (Ex n) devices are suitable; it is critical the temperature class must also
conform. The reader should note that for the US the often used NEC 500 standard does not
distinguish between Zone 0 and Zone 1.
For Zone 1 the use of flameproof (Ex d) enclosures for complex equipment is generally
discouraged due to their size weight and cost. For complex bespoke electronics purged
enclosures (Ex p) are often used. For mass produced electronics such as monitors and PC’s
the quartz sand filled (Ex q) concept is often applied, and large switchgear often uses oil
immersion (Ex o).
For Zone 2 there are an increasing number of choices of protection types.
Both Ex i(a or b) and Ex p require additional protective devices to ensure the sensor or
equipment operates safely. Intrinsic safety requires the device in the hazardous area to be
suitably certified and that a suitably certified isolator or barrier protect the cabling to that
device from the safe area. Ex p enclosure have a suitably certified purging device attached
to ensure the enclosure is purged of flammable gas before the power is applied and that a
positive pressure is maintained within the enclosure during its operation.
Many hazardous sites choose a to use a blanket Zone 1 policy where instrumentation is
intrinsically safe (Ex i(a or b)) and motors are increased safety (Ex e). However if the Zoned
Areas can be reduced by analysis then the cost to install and maintain devices can be
considerably reduced.
Page 2
5 Area Classification
It is the area classification that defines the type of Zone or Division
Material
Flammable Material
Continuously Present
(> 10% of the time)
Flammable Material
Often Present
(0.1 – 10% of the time)
Flammable Material
Rarely Present
(0 to 0.1% of the time )
EU and
US
IEC under under NEC
EN/IEC
505
60079-10
Zone 0 for Zone 0
gasses or
Zone20 for
dusts
Zone 1 for Zone 1
gasses or
Zone 21
for dusts
Zone 2 for Zone 2
gasses or
Zone 22
for dusts
US
under NEC
500
CAN
under CEC
Sect 18
CAN–under
CEC Annex
J
Division 1
Zone 0
Division 1
Division 1
Zone 1
Division 1
Division 2
Zone 2
Division 2
6 Equipment Protection Level (EPL)
The EPL as defined in EN 60079-0 is often used to specify the minimum standard for
equipment in a particular zone – It differs from the ATEX directive (Directive 94/9/EC) in
that it distinguishes between Gas and Dust within the Equipment Groups.
II fors,
EN 60079
Directive 94/9/EC
EPL
Group
Zone Equipment Equipment
Explosion Risk
Examples
Group
Category
of
suitable
types of
protection
Ma
I
I
M1
Energized
(mines)
Mb
I
(mines)
Ga
II
(gases)
Gb
II
(gases)
I
M2
De-energized in presence of
an explosive atmosphere
0
II
1G
1
II
2G
Explosive atmosphere
present > 1000 hours/year
(> 10% of the time)
Explosive atmosphere
present between 10 and
1000 hours/year (0.1 –
10% of the time)
ia, ma
ib, mb,
px, py, e,
o, q, s
Page 3
EPL
EN 60079
Directive 94/9/EC
Group
Zone Equipment Equipment
Group
Category
Gc
II
(gases)
2
II
3G
Da
III
(dusts)
20
II
1D
Db
III
(dusts)
21
II
2D
Dc
III
(dusts)
22
II
3D
Explosion Risk
Explosive atmosphere
between 1 and 10
hours/year (0 to 0.1% of
the time )
Explosive surface > 1000
hours/year (> 10% of the
time)
Explosive surface between
10 and 1000 hours/year
(0.1 – 10% of the time)
Explosive surface between 1
and 10 hours/year (0 to
0.1% of the time )
Examples
of
suitable
types of
protection
n, ic, pz
ia
ib
ic
7 Markings
All equipment designed for use within a Hazardous area shall be suitably marked
7.1 EU Markings
Within the EU this shall include a Directive marking (94/9/EC) in front of the standard (EN
60079) marking. If the device is certified for use in both Gas and Dust then there shall be
two lines of markings.
7.1.1
European
Conformity
Marking
European Directive 94/9/EC (ATEX) Part
ID of Notified
Body
involved in
production
control stage
1275
Type of
Equipment
Protection Group
II
I for
mines,
II for
other
areas
Category
2
1 for Zone 0 or
20.
2 for Zone 1 or
21.
3 for Zone 2 or
22.
Type of
Explosive
Atmosphere
G
G for gas,
vapour or mist.
D for dust.
Page 4
7.1.2
Standard EN 60079 Part
For Gases
European
Standard
Explosion
Protected
Type of
Protection
Group
Gas
Group
Temperature
Class
EPL
E
x
ia
II
B
T4
Gb
T1 to T6
Ga, Gb
or Gc
I for
mines,
II for
other
areas
A, B,
B+H2, C
For Dusts
European
Standard
Explosion
Protecte
d
Type of
Protection
Group
Dust Group
Maximum
Surface
Temperature
EPL
E
x
ia
III
C
120oC
Da
I for
mines,
II for
other
areas
A, B, C
Actual
value
Da, Db
or Dc
Notes
(1) If the temperature range is outside the range -20 to +40degC it must be marked
also.
(2) Where certified for use in both Gas and Dust environments both gas and dust
markings must be shown as separate lines and the EPL suffixes are not required.
7.2 IEC and Canada (CEC Sect.18)
European
Standard
Explosion
Protected
Type of
Protection
Group
Gas
Group
Temperature
Class
EPL
E
x
ia
II
B
T4
Gb
I for
mines,
II for
other
areas
A, B,
B+H2, C
T1 to T6
Ga, Gb
or Gc
Page 5
7.3 US (under NEC 500) and Canada (under CEC Annex J)
Type of Protection
Explosion-proof with I.S. Outputs
Division 1
Groups A,B,C,D,
Permitted Division
Permitted Gas Groups
Permitted Class
Class I
T5
Temperature Class
Notes
(1) If the temperature range is outside the range -25 to +40degC it must be marked
also.
7.4 US (Under NEC 505)
Permitted
Class
Class I,
Permitted
Zone
Zone1,
American Explosion
National
Protected
Standard
A Ex
Type of
Protection
I.S
Output
d
[ia]
Group Gas
Group
II C
Temp
.
Class
T5
Notes
(1) If the temperature range is outside the range -20 to +40degC it must be marked
also.
8 Principals of Protection
There are various methods employed to prevent an explosion occurring either by design of
the device itself or in combination with a form of external protection or monitoring. Different
methods are suitable for the intended Zone. The standards for EU, US and Canada do differ
and so all three are shown.
8.1 NO SPARKS OR HOT SURFACES
8.1.1
Code
Ex e
Ex e
AEx e
Ex e
Increased Safety
Region
EU
IEC
US
CAN
Use
Zone 1
Zone 1
Class I, Zone 1
Class I, Zone 1
Standard
EN 60079-7
IEC 60079-7
ISA 60079-7
CSA E60079-7
8.1.2
Code
Ex nA
Ex nA
AEx nA
Ex nA
Non-Sparking
Region
EU
IEC
US
CAN
Use
Zone 2
Zone 2
Class I, Zone 2
Class I, Zone 2
Standard
EN 60079-15
IEC 60079-15
ISA 60079-15
CSA E60079-15
Page 6
Notes
(1) For particular non-incendive Fieldbus applications in hazardous areas, FNICO devices
are covered by the IEC/EU standard IEC/EN 60079-27
8.1.3
Code
(NI)
(NI)
8.2
Non-Incendive (US & CAN Only)
Region
Use
US
Class I, Div. 2
CAN
Class I, Div. 2
Standard
FM 3611
C22.2 No. 213
CONTAIN THE EXPLOSION AND LIMIT THE FLAME
8.2.1
Code
Ex d
Ex d
AEx d
Ex d
Flame proof
Region
EU
IEC
US
CAN
Use
Zone 1
Zone 1
Class I, Zone 1
Class I, Zone 1
Standard
EN 60079-1
IEC 60079-1
ISA 60079-1
CSA E60079-1
8.2.2
Code
Ex q
Ex q
AEx q
Ex q
Powder filled
Region
EU
IEC
US
CAN
Use
Zone 1
Zone 1
Class I, Zone 1
Class I, Zone 1
Standard
EN 60079-5
IEC 60079-5
ISA 60079-5
CSA E79-5
8.2.3
Code
Ex nC
Ex nC
AEx nC
Ex nC
Enclosed Break
Region
EU
IEC
US
CAN
Use
Zone 2
Zone 2
Class I, Zone 2
Class I, Zone 2
Standard
EN 60079-15
IEC 60079-15
ISA 60079-15
CSA E60079-15
8.2.4
Code
(XP)
(XP)
8.3
Explosion-proof (US & CAN Only)
Region
Use
US
Class I, Div.1
CAN
Class I, Div.1
Standard
FM 3615
C22.2 No. 30
LIMIT THE ENERGY AND SURFACE TEMPERATURE
8.3.1
Code
Ex ia
Ex ib
Ex ic
Ex ia
Intrinsic Safety
Region
EU
EU
EU
IEC
Use
Zone 0
Zone 1
Zone 2
Zone 0
Standard
EN 60079-11
EN 60079-11
EN 60079-11
IEC 60079-11
Page 7
Code
Ex ib
Ex ic
AEx ia
AEx ib
(IS)
Ex ia
Ex ib
(IS)
Region
IEC
IEC
US
US
US
CAN
CAN
CAN
Use
Zone 1
Zone 2
Class I, Zone 0
Class I, Zone 1
Class I, Div. 1
Class I, Zone 0
Class I, Zone 1
Class I, Div. 1
Standard
IEC 60079-11
IEC 60079-11
FM 3610
FM 3610
FM 3610
CSA E60079-11
CSA E60079-11
C22.2 No. 157
Notes on Intrinsic Safety
1- For associated intrinsically safe apparatus suitable for installation in a hazardous
location, the symbols for the type of protection “ia” or “ib” are enclosed within square
brackets, e.g. Ex e [ia] IIC T4.
2- For associated intrinsically safe apparatus not suitable for installation in a hazardous
location, both the symbol “Ex” and the symbol for the type of protection “ia” or “ib” are
enclosed within the same square brackets, e.g. [Ex ia] IIC ; in this case, a temperature class
is not included.
3- For particular Intrinsically Safe Fieldbus applications in hazardous areas, FISCO devices
are covered by the IEC/EU standard IEC/EN 60079-27.
8.3.2
Code
Ex nL
Ex nL
AEx nC
Ex nL
8.4
Limited Energy
Region
EU
IEC
US
CAN
Use
Zone 2
Zone 2
Class I, Zone 2
Class I, Zone 2
Standard
EN 60079-15
IEC 60079-15
ISA 60079-15
CSA E60079-15
Use
Zone 1
Zone 1
Zone 1
Zone 1
Zone 2
Zone 2
Class I, Div.1
Class I, Div.1
Class I, Div.1
Class I, Div.1
Class I, Div.2
Class I, Div.2
Standard
EN 60079-2
IEC 60079-2
EN 60079-2
IEC 60079-2
EN 60079-2
IEC 60079-2
NFPA 496
NFPA 496
NFPA 496
NFPA 496
NFPA 496
NFPA 496
EXCLUDE THE FLAMMABLE GAS
8.4.1
Code
Ex px
Ex px
Ex py
Ex py
Ex pz
Ex pz
Type X
Type X
Type Y
Type Y
Type Z
Type Z
Pressurised
Region
EU
IEC
EU
IEC
EU
IEC
US
CAN
US
CAN
US
CAN
Page 8
Code
AEx px
Ex px
AEx py
Ex py
AEx pz
Ex pz
Region
US
CAN
US
CAN
US
CAN
Use
Class I, Zone
Class I, Zone
Class I, Zone
Class I, Zone
Class I, Zone
Class I, Zone
1
1
1
1
2
2
Standard
ISA 60079-2
CSA E60079-2
ISA 60079-2
CSA E60079-2
ISA 60079-2
CSA E60079-2
8.4.2
Code
Ex nR
Ex nR
AEx nR
Ex nR
Restricted Breathing
Region
EU
IEC
US
CAN
Use
Zone 2
Zone 2
Class I, Zone 2
Class I, Zone 2
Standard
EN 60079-15
IEC 60079-15
ISA 60079-15
CSA E60079-15
8.4.3
Code
Ex ma
Ex ma
Ex mb
Ex mb
AEx m
Ex m
Encapsulation
Region
EU
IEC
EU
IEC
US
CAN
Use
Zone 0
Zone 0
Zone 1
Zone 1
Class I, Zone 1
Class I, Zone 1
Standard
EN 60079-18
IEC 60079-18
EN 60079-18
IEC 60079-18
ISA 60079-18
CSA E60079-18
8.4.4
Code
Ex o
Ex o
AEx o
Ex o
Oil Immersion
Region
EU
IEC
US
CAN
Use
Zone 1
Zone 1
Class I, Zone 1
Class I, Zone 1
Standard
EN 60079-6
IEC 60079-6
ISA 60079-6
CSA E79-6
9 Temperature Classes
Equally important are the permissible temperatures within the Zone. A device will have a
Temperature Class marking; this relates to the maximum theoretical surface temperature it
may achieve in operation. The Area Classification will define the maximum acceptable T
class for the Zone.
Maximum Surface
Temperature oC
450
300
280
260
230
EU and IEC Class
US & CAN Class
T1
T2
T1
T2
T2A
T2B
T2C
Page 9
Maximum Surface
Temperature oC
215
200
180
165
160
135
120
100
85
EU and IEC Class
US & CAN Class
T2D
T3
T3A
T3B
T3C
T4
T4A
T5
T6
T3
T4
T5
T6
10 Apparatus Grouping
It is important especially if acetylene or hydrogen may be present in the Zone that the
intended device is suitable for that Group, many do not have IIC for example.
Typical Gas
Methane
Acetylene
Hydrogen
Ethylene
Propane
Metal dust
Carbon Dust
Flour
Sawdust
EU and IEC Group
Group I
Group IIC
Group IIB + H2
Group IIB
Group IIA
Group IIIC
Group IIIC
Group IIIB
Group IIIA
US & CAN Group
Mining
Class I/Group A
Class I/Group B
Class I/Group C
Class I/Group D
Class II/Group E
Class II/Group F
Class II/Group G
Class III/No Group
11 Ingress Protection
The ingress protection of a device or enclosure may assist in the choice of enclosures
suitable for the Group and hence the Zone. IP54 is the minimum acceptable for Groups I
and II. For Groups IIIA and IIIB: IP5X is the minimum, whilst for III and IIIC: IP6X is the
minimum. Note that any penetration into the enclosure will compromise that IP rating unless
the insert is suitably IP rated itself!
Protection against
Solid Bodies
Protection against
Liquids
6
5
IP
0
1
2
3
4
5
6
for
for
for
for
for
for
for
No Protection
objects > 50mm
objects > 12mm
objects >2.5mm
objects > 1mm
Dust Protected
Dust Tight
0
1
2
3
4
5
6
7
8
for
for
for
for
for
for
for
for
for
No Protection
vertically (90o) dripping water
75 to 90 dripping water
Sprayed Water
Splashed Water
Water Jets
Heavy Seas
Effects of Immersion
Indefinite Immersion
Page 10