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ATEX & IECEx Zones & Equipment

What is a potentially explosive atmosphere?

An atmosphere can become potentially explosive when it contains dangerous levels of flammable gases, mists or dusts.
If a source of ignition is then introduced, combustion can occur.

The risk of explosion can be reduced by preventing the release or build-up of flammable substances and by eliminating sources of ignition.

However first we need to understand if or how long an explosive atmosphere could be present.

This is where zones are introduced and in general this is based on historical information as per;

Zone (Gas)
Zone (Dust)
Definition
0
20
>1000 hours per year
1
21
Between 10 & 1000 hours per year
2
22
<10 hours per year

What ATEX Category Equipment should I use

The following table shows Zones in relation to ATEX safety categories that equipment is required to meet to ensure the correct level of protection is applied within a potentially explosive atmosphere;

Zone (Gas)
Zone (Dust)
Danger / Protection Level
ATEX Safety Category Required*
Zone 0
Zone 20
Constant danger/Very high.
Explosive hazard always present.
Category 1 equipment.
Zone 1
Zone 21
Potential danger/high.
Explosive hazard occasionally present during normal working practices.
Minimum of Category 2 equipment.
Zone 2
Zone 22
Minor danger/normal.
Explosive hazard not likely or only for short periods
Minimum of Category 3 equipment.
*unless risk assessment states a higher or lower category is required

What IECEx Equipment Protection levels should I use

The following table shows Zones in relation to Equipment Protection Levels that equipment is required to meet to ensure the correct level of protection is within a potentially explosive atmosphere;
Zone (Gas)
Zone (Dust)
Definition
Equipment Protection Level (EPL) Required*
Zone 0
Zone 20
Constant danger/Very high.
Explosive hazard always present.
Ga / Da
Zone 1
Zone 21
Potential danger/high.
Explosive hazard occasionally present during normal working practices.
Gb / Db
Zone 2
Zone 22
Minor danger/normal.
Explosive hazard not likely or only for short periods
Gc / Dc
*unless risk assessment states a higher or lower EPL is required

What Temperature Class should I use

The following table shows Temperature Class, Max Surface Temperature (in normal & fault specific conditions)  in relation to which Areas they are suitable for use.
Equipment Temperature Class
Maximum surface temperature °C
Suitable in Area with “T Class”
T1
450
T1 only
T2
300
T1 – T2
T3
200
T1 – T3
T4
135
T1 – T4
T5
100
T1 – T5
T6
85
T1 – T6

What Gas Group should I use

The following table shows Gas Sub Groups for surface industries, their example/typical substance in relation to which “gas areas” they are suitable for use;

Equipment Gas Group
Typical Substances
Suitable in Area with “Gas Group”
IIC
Acetylene & Hydrogen
IIC, IIB & IIA
IIB
Ethylene
IIB & IIA
IIA
Propane
IIA ONLY
poster

Explosion Protection at a glance

Markings, Comparisons and Applications
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