Protection Concepts

ZONE

HAZARD

PROTECTION CONCEPTS

0

In which an explosive gas/air mixture is continuously present for long periods

Exia or Exs

1

In which an explosive gas/air mixture is likely to occur in normal operation.

Exd. Exe, Exib, Exp, Exia, Exs

2

In which an explosive gas/air mixture is not likely to occur in normal operation.

All concepts suitable for
Zone 0 & 1, ExN, ExO and Exq

Standards For Methods Of Protection

METHOD OF PROTECTION

PERMITTED ZONE
OF USE IN UK

CODE LETTER
IEC, EX.., CENELEC, EEX

General requirement

-

-

Oil immersion

2

o

Pressurisation

1 or 2

p

Powder filling

2

q

Flameproof

1 or 2

d

Increased safety

1 or 2

e

Intrinsic safety

* 0, 1 or 2

ia or ib

Non-incendive

2

n #

Encapsulation

1 or 2

m

Special

1 or 2

s

* ia: Zone 0,1,2. ib: Zone 1,2. not Zone 0. # n: used locally in UK.

Gas Grouping

Temperature Classification

GAS # GROUP
CENELEC
EN 50 014, IEC

REPRESENTATIVE GAS

T Class / IEC 79-7

Max. surface temp ° C

I * (mining)

Methane

T1

450 ° C

IIA

Propane

T2

300 ° C

IIB

Ethylene

T3

200 ° C

IIC

Hydrogen

T4

135 ° C

T5

100 ° C

T6

85 ° C

Certification Code
(CENELEC marking information - example [EEx ia] IIC T4)

[

E

Ex

ia

]

IIC

T4

Associated apparatus*

Certified to the CENELEC standard

Explosion protected

Protection
concept (IS)

Associated
apparatus*

Apparatus
group
(gas group)

Temperature
classification
(not Gp I)

* (located in safe area and may be connected to hazardous area)

DEVICE GROUP

DEVICE CATEGORY

ZONE

I

M = mining

–

Mining

M 1

–

Pit gas &/or flammable dusts

M 2

–

II

G = gas

Other areas

1 G

0, 1, 2

Explosive atmosphere

2 G

1, 2

3 G

2

D is added after G in the certification class number

D = dust

(i.e. GD) if device is dust category approved also

1 D

20, 21, 22

2 D

21, 22

3 D

22

Explanation of the categories:

1 - Very high safety = device safety must be guaranteed even in case of rare device failures, e.g. simultaneous failure of two components.

2 - High safety = device safety must be guaranteed if frequent failures can be expected, e.g. failure of one component.

3 – Safe in normal operation = device safety must be guaranteed in normal operation.

Note: A number in brackets before device category designation signifies that the device meets the requirements of an additional category to the main one that is specified.

Example: II (1) 2G signifies that the device meets requirements for both
1 G and 2 G categories