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Hazardous areas are locations in which an explosive atmosphere may develop under
certain conditions. The explosive atmosphere is a mixture of air and
flammable substances in the form of gas, vapour, mist or dust in which,
after the ignition, the combustion spreads rapidly to the whole mixture
(explosion). In compliance with the 1999/92/EC directive, the user is
bound to subdivide the hazardous areas in classes according to the frequency
and the period of time in which an explosive atmosphere can occur. In
the presence of substances that emit gasses and flammable vapours, the
classification is carried out in compliance with the 60079-10 EN standard
and generates three zones with different risk levels:
- Zone
0: area in which an explosive gas atmosphere is present continuously
or for long periods.
- Zone
1: area in which an explosive gas atmosphere is likely to occur in
normal operation.
- Zone
2: area in which an explosive gas atmosphere it is not likely to occur
in normal operation and, if it does occur, is likely to do so only
infrequently and will exist for a short period only.
In the
areas with combustible dusts the classification generates three dangerous
zones (20, 21 and 22) with risk levels defined similarly to zone 0,
1 and 2 respectively.
The 94/9/EC
(ATEX) directive classified the equipment in three categories with different
protection levels to be used in the different areas, in order to guarantee
always the same safety level.
| COMBUSTIBLE
SUBSTANCES |
:-- |
GAS AND VAPOUR
|
DUST
|
|
|
| AREAS |
|
0
|
1
|
2
|
20
|
21
|
22
|
|
| EQUIPMENT
CATEGORIES |
|
1G
|
2G
|
3G
|
1D
|
2D
|
3D
|
|
|
