Zone 20
In Zone 20, normal operation, dangerous, potentially explosive atmosphere can form over longer periods at
regular intervals the form cloud combustible dust contained the air.
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Chapter The external lightning protection system
.3. These
zones are always three-dimensional areas three-
dimensional space.000x
≥ 1x/month,
< 3x/day
Longer than 0.
A further subdivision the potentially explosive areas
makes distinction between combustible gases and
combustible dusts.
Zone 21
In Zone 21, normal operation, dangerous, potentially explosive atmosphere can form occasionally the form
of cloud combustible dust contained the air.5 hrs
Definition zones
Ex zones Description
Zone 0
In Zone normal operation, dangerous, potentially explosive atmosphere can form over longer periods at
regular intervals mixture air combustible gases, vapours mist.
Zone 22
In Zone 22, normal operation, dangerous, potentially explosive atmosphere can normally not, only briefly,
form the form cloud combustible dust contained the air.
Zone 2
In Zone normal operation, potentially explosive atmosphere can normally not, only briefly, form mix-
ture air combustible gases, vapours mist.5 hrs,
shorter than hrs
Zone Zone 22: Normally short form-
ation potentially explosive atmospheres
≥ 1x,
< 10x
≥ 1x/year,
< 1x/month
Shorter than 0.
Intervals the occurrence potentially explosive atmospheres
Level risk
Interval occurrences
of mixtures (annual)
Interval occurrences of
mixtures (differentiated)
Dwell times the
mixtures
Zone Zone 20: Constant frequent form-
ation potentially explosive atmospheres
Greater than for Zone 1,
> 1.
Zone 1
In Zone normal operation, atmosphere can occasionally form mixture air combustible gases, va-
pours mist.TBS
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2.2 Assignment the zones
Potentially explosive areas are divided into zones
according the duration and frequency the occur-
rence potentially explosive atmospheres.000x
Greater than for Zone 1,
> 3x/day
Longer than for Zone 1
Zone Zone 21: Occasional formation of
potentially explosive atmospheres
≥ 10x,
< 1
