Intro4u2u

Hazardous Location
Classification
Hazardous locations outside North
America are classified by gas group
and zone.
Group
Electrical equipment is divided into
two groups. Group I covers electrical
equipment used in mines, and Group
II covers all other electrical equipment.
Group II is further subdivided
into three subgroups: A, B, and C.
The specific hazardous materials within
each group can be found in CENEChapter
9. Standards and Approvals
187
LEC EN 50014, and the automatic
ignition temperatures for some of
these materials can be found in IEC
60079-4.

Group I (Mining): Atmospheres
containing methane, or gases or vapors
of equivalent hazard.

Group IIA: Atmospheres containing
propane, or gases or vapors of
equivalent hazard.

Group IIB: Atmospheres containing
ethylene, or gases or vapors of
equivalent hazard.

Group IIC: Atmospheres containing
acetylene or hydrogen, or
gases or vapors of equivalent hazard.
Note
An apparatus approved
for one subgroup in
Group II may be used in
the subgroup below it;
for example, Group IIC
may be used in Group
IIB locations.
Zone
The zone defines the probability of
hazardous material being present in
an ignitable concentration in the surrounding
atmosphere:

Zone 0: Location where an explosive
concentration of a flammable
gas or vapor mixture is continuously
present or is present for long periods.
The area classified as Zone 0, although
not specifically defined, is contained
within the United States and
Canada classifications of a Division 1
location and constitutes an area with
the highest probability that an ignitable
mixture is present.

Zone 1: Location where an explosive
concentration of a flammable
or explosive gas or vapor mixture is
likely to occur in normal operation.
The area classified as Zone 1 is contained
within the United States and
Canada classifications of a Division 1
location.

Zone 2: Location in which an
explosive concentration of a flammable
or explosive gas or vapor mixture
is unlikely to occur in normal operation
and, if it does occur, will exist
only for a short time. Zone 2 is basically
equivalent to the United States
and Canadian classifications of a Division
2 location.
Temperature Code
A mixture of hazardous gases and air
may be ignited by coming into contact
with a hot surface. The conditions under
which a hot surface will ignite a
gas depends on surface area, temperature,
and the concentration of the
gas.
The approval agencies test and establish
maximum temperature ratings for
the different equipment submitted for
approval. Group II equipment that has
been tested receives a temperature
code that indicates the maximum surface
temperature attained by the
equipment. It is based on a 40 C
(104 F) ambient temperature unless
a