This document provides an overview of hazardous area classification. It begins with a brief history of classification systems developed after accidents in coal and oil/gas industries. It then defines hazardous areas and explains the need for classification to control explosion hazards. The key classification systems of Class/Division and Zone are described, including their definitions of degree of hazard. Gas groups and temperature classes are also covered. The document provides a summary of the classification of Classes I, II, and III and explains common protection techniques used for electrical equipment in hazardous areas.

1. • History of Hazardous area classification
• Hazardous area classification
• Class, Division and Zone classification system
• Gas group and temperature class
• Understanding of type Ex:- i, d, e, p, n, o, q, s etc.
• IP protection
Hazardous Area Classification
Content:

2. • Area Classification
• Why ? Where ? How ? Who ? When ?
• Severe accidents in coal mines occurred through the world in the
19th and 20th century (thousands of casualties).
• Causes : Result of ignition of Fire damp by sparks (often
generated by electrical apparatus) leading to those catastrophic
accidents
Hazardous Area Classification
• Oil & gas and chemical industries also generated many accidents
(fire ,explosion).

3. • The first hazardous areas recognized in coal mines.
• Methane gas, which is absorbed by coal, later escapes from the
coal once it is mined.
• The methane gas, which is lighter than air, would occasionally
be ignited by the miner’s candles
• In 1815 Sir Humphry Davy, who developed an oil lamp that
prevented the propagation of the flame by means of a close-
meshed screen.
• Specially protected (totally enclosed) electrical motors and
apparatus in coal mines developed for explosion- protection
• Year 1900 - the International Electro technical Commission (IEC)
was founded in Switzerland
• The journey of hazardous area classification started
Hazardous Area Classification - History

4. Petroleum Rules, 1976
An area shall be deemed to be a hazardous area, where:
• Petroleum having FP below 65 0 C or any inflammable gas or
vapor in concentration capable of ignition is likely to be present.
• Petroleum or any inflammable liquid having FP above is likely to
be refined, blended or stored at or above its FP
Hazardous Area - Definition
IS 5572
Hazardous area is an area in which an explosive gas atmosphere
is present, or likely to be present, in quantities such as to
require special precautions for the construction, installation and
use of electrical apparatus.

5. Hazardous Area Classification
Why Classification area is required
• It is clear from ignition triangle that fire/
explosion / combustion can be eliminated or
avoided if any one component of the triangle is
eliminated.
• After identifying these area it is possible to
control the fire, explosion or combustion hazard
by taking proper precautions at design level itself

6. Hazardous Area Classification
1 Hazardous Non Hazardous
2 Classified Un Classified
3 Class I- Division 1 Class I- Division 2
4 Class II - Division 1 Class II - Division 2 Less
known
5 Class III - Division 1 Class III - Division 2 Less
known
6 Class I - Zone 0 Class I - Zone 1
Class I - Zone 2
Less
known
• The Class/Division system is used predominately in the
United States and Canada,
• Rest of the world generally uses the Zone system.

7. Hazardous Area Classification – What?
What is Hazardous Area Classification?
Area classification is:
• Is a method of analysing and classifying the explosive
environment,
• Takes into account gas groups (based on ignition energy) and
temperature classes.
• Is to facilitate proper selection and installation of apparatus
to be used safely in that environment,
• The basic underlying philosophy is SAFETY of life and property
by quantifying the location.

8. Hazardous Area Classification
Flammable Gases or Vapors, Dust and Fibers are or may be
present in the air in quantities sufficient to produce explosive or
ignitable mixtures
Class I
Gas &
Vapor
Division
1
Class II
Dust
Class III
Fibers &
Flying
Division
2
Division
1
Division 2 Division 1
Division
2

9. Hazardous Area Classification
Area is classified based on the
properties of the flammable vapors,
liquids, gases, or combustible dust or
fiber that may be present and the
chance that a flammable or combustible
concentration would be present.
Class I
Gas &
Vapor
Division
1
Class II
Dust
Class III
Fibers &
Flying
Division
2
Division
1
Division 2 Division 1
Division
2
The Class designations tell you what type of flammable or combustible material
is present. Class designations use Roman numerals.
The Division designation tells you to what degree the hazard is present.
Division designations and Zone designations use Arabic numbers
Thus Area classifications is based on Classes, Divisions, and Groups which are
factors combined to define the hazardous conditions of a specific area

10. Hazardous Area Classification
Flammable Gases or Vapors are or may be present in the air in quantities
sufficient to produce explosive or ignitable mixtures
Class I
Gas &
Vapor
Division
1
Division 2
• Where gases or vapors exist
under normal conditions
• May exist frequently because
of repair or maintenance
• Might exist due to faulty
equipment or processes
• Gases or liquids in closed containers or
systems and would escape only with
accidental rupture or equipment breakdown
• Ignitable gases or vapors are prevented by
positive mechanical ventilation and would
become hazardous through failure or
abnormal operations of the ventilating
equipment
• Area adjacent to Class I Division I and to
which ignitable concentrations of gases or
vapors might occasionally be communicated

11. Areas that are hazardous because of the presence of
combustible dust.
Class II
Dust
Division
1
Division 2
• Combustible dust in air under
normal conditions in quantities
sufficient to produce explosive or
ignitable mixtures; or
• Mechanical failure or abnormal
operation of equipment releases
dust and might provide a source of
ignition; or
• Combustible dust of a electrically
conductive nature (i.e. magnesium
and aluminum dust)
• Combustible dust not normally in high
enough quantities to produce explosive
or ignitable mixtures
• Dust accumulations will normally be
insufficient to interfere with the normal
operation of electric equipment or
other apparatus
• Accumulation on, in, or near electrical
equipment may cause heat build-up
and be ignitable by equipment failure
Hazardous Area Classification

12. Areas that are hazardous because of the
presence of easily ignitable fibers or flying.
Class III
Fibers &
Flying
Division
1
Division 2
• Location in which easily
ignitable fibers or materials
producing combustible flyings
are handled, manufactured,
or used.
•Location in which easily ignitable
fibers are stored or handled,
other than in the process of
manufacture.
Hazardous Area Classification

13. A: Acetylene
B: Hydrogen, etc.
C: Ester, etc.
D: Hydrocarbons. fuels
Class I
Gas &
Vapor
Division
1
Class III
Fibers&
Flyings
Class II
Dust
Division
2
Division
1
Division 2 Division 1
Division
2
GROUP
E: Metal dusts (conductive
& explosive)
F: Carbon dusts (some are
conductive, all are
explosive)
G: Flour, starch, grain,
combustible plastic or
chemical dust (explosive)
No specific group
Based on Ignition and
explosion characteristic
Hazardous Area Classification
GROUP
GROUP

14. Class I Class II Class III
Flammable gas, vapor or
mists
Combustible Dusts Fibers and
Ignitable Flyings
Division 1
Division 2
Division 1
Division 2
Division 1
Division 2
Group A
Acetylene
Group E
Metal dust
Not Grouped
Rayon Cotton etc.
Group B
Hydrogen etc.
Group F
Carbon black, coal, coke
dust etc.
Group C
Ethylene, Ethyl Easter
Group G
Flour, starch grain, dust etc.
Group D
Acetone, Benzene, butane ,
Propane
NEC - National Electric Code

15. The alternative Zone Classification System only covers
Class I installations.
Class I
Gas &
Vapor
Zone 0 Zone 2
“Zone Classification System" (Alternative Method)
Zone 1
Hazardous Area Classification
Europe and India as per IEC – Zone system

16. Class I
Gas &
Vapor
Zone 0 Zone 2
Zone 0 location is:
• Ignitable flammable gases
or vapors are present
continuously;
• Ignitable flammable gases
or vapors are present for
long periods of time.
Zone 2 location is:
• Ignitable flammable gas or vapor
not likely or for short period only;
or
• Confined in closed systems or
containers but could escape due to
accident; or
• Ignitable accumulation prevented
by positive ventilation; or
• Area adjacent to Class I Zone I from
which ignitable concentrations
could be communicated
“Zone Classification System" (Alternative Method)
Zone 1
Zone 1 location is:
• Ignitable flammable gases or vapors are likely
under normal conditions; or
• Ignitable conditions may exist because of repair,
maintenance or leakage; or
• Equipment breakdown may cause electric
equipment to be a source of ignition;
• A location adjacent to a Class I, Zone 0 location
where ignitable concentrations of vapors could
be communicated

17. Class I
Gas &
Vapor
Zone 0 Zone 2
Zone 0 location is:
Explosive Mixtures
continuously present /
Present for long (>1000
Hrs/Yr). e.g. Inside
Tanks, Vessels etc.
Zone 1 location is:
Explosive Mixtures likely to occur in normal operation / (Between
10 to 1000 Hrs/ Yr). i.g. Production Area, area surrounding zone 0.
“Zone Classification System" (Alternative Method)
Zone 1
Zone 2 location is: Explosive
Mixtures not likely to occur /occur
short duration in normal
operation (<10 Hrs/ Yr).
NEC: 2 Divisions (Div: 1 & 2)
Division I: Comprising of Area Same as Zone 0 & 1.
Division II: Comprising of Area Same as Zone 2.

18. Hazardous Area Classification- Degree of Hazard
Zones and Divisions
Zone Definitions- Europe and India as per
IEC
Division Definitions-North
America – NEC 505
Zone
0
Explosive Mixtures continuously
present / Present for long (>1000
Hrs/Yr or >10% of the time.) e.g.
Inside Tanks, Vessels, drum etc.
Div
1
Usually or Frequently
hazardous vapors present
during normal operation
Comprising of Area Same
as Zone 0 & 1.
Zone
1
Explosive Mixtures likely to occur
in normal operation / (Between 10
to 1000 Hrs/ Yr or 0.1– 10% of the
time. ). e. g Production Area, area
surrounding zone 0.
Zone
2
Explosive Mixtures not likely to
occur /occur short duration in
normal operation (<10 Hrs/ Yr or )
0 - 0.1% of the time.
Div
2
NOT hazardous during
normal operations
Comprising of Area Same
as Zone 2.
Zone 0 and 1 = Div. 1

19. Class I
Gas &
Vapor
Zone 0 Zone 2
Group
Zone 1
• The zone system (0, 1, 2) has three “groups”, designated IIA,
IIB, and IIC, with group IIC containing the most volatile gases,
and groups IIA and II B containing gases or vapors that are
progressively less volatile.
• Substances classified under groups A and B in the division
system generally fall under group IIC of the zone system.
• Gas group system
• IIA - Acetylene + Hydrogen – (Less Dangerous)
• IIB – Ethylene
• IIC – Propane – (Most Dangerous)
Zone Classification System- Gas Group

20. Summary of Class I, II, III Hazardous Locations
Classes Groups Divisions
1 2
Class I
Gases, Vapors
& Liquids
A: Acetylene
B: Hydrogen, etc.
C: Ester, etc.
D: Hydrocarbons. fuels
Normally explosive
and hazardous
Not normally
present in an
explosive
concentration but
may accidentally exist
Class II
Dusts
E: Metal dusts
(conductive and explosive)
F: Carbon dusts
(some are conductive, all
are explosive)
G: Flour, starch, grain,
combustible plastic or
chemical dust (explosive)
Ignitable quantities
of dust are or
may be in
suspension, or
conductive dust
may be present
Dust not normally
suspended in an
ignitable
concentration
(but may accidentally
exist). Dust layers
are present.
Class III
Fibers & Flying
Textiles, woodworking etc.
(easily ignitable but not
usually explosive)
Handled or used in
manufacturing
Stored or handled
in storage
(exclusive of
manufacturing)
Hazardous Location Summary

21. North American Atmosphere Classification
Zone System Gas (Class 1) Division System Gas (Class 1)
IIC Acetylene + Hydrogen
Type A Acetylene
Type B Hydrogen, Propylene oxide
IIB Ethylene Type C Ethylene, Ethel ether
IIA Propane Type D Propane, acetone, benzene
Division System Dust (Class 2)
Type E Metal Dust
Type F Carbon Dust
Type G Grain Dust
Division System Fibers (Class 3)
Textiles and woodworking flying
Gas group

22. Flammable Liquid (as per IS:5572)
Classified on basis of Flash Point.
Class A: Flash Pt < 23oC.
They produce large volumes of vapour
Class B: 23oC<Flash Pt<65oC
Class C: 65oC<Flash Pt<93oC

23. • Explosion proof equipment, installed within the Ex area, is
divided into 6 temperature classes (T1 to T6).
• Temperature class is not – as it is often wrongly believed – the
operating temperature range of the equipment, but the
maximum permissible surface temperature of the equipment,
in relation to + 40°C ambient temperature on any surface area,
and should not be exceeded at any time.
• The maximum surface temperature must remain below the
ignition temperature of the all flammable substances at all times.
• The equipment requirements rise from T1 to T6.
Temperature Class – Stage 3 in classification

24. • The max surface temp. of exposed surface of equipment
must always be lower than Auto-Ignition Temp of the
Prevailing Gas.
Class
T1
T2
T3
T4
T5
T6
Temperature (oC)
450
300
200
135
100
85
Temp. oF
842
572
392
275
212
185
Temperature Class - oC And oF
Maximum surface temperature

25. • Example:
• Class I, Zone 1, AEx, ia, IIC, T6
• Class I: Class
• Zone 1: Zone
• AEx: American Standard (European standard are EEx)
• Ex: Explosion protection
• ia: Type of protection
• IIC: Type of Gas or Gas Group
• T6: Temperature Class or code
Equipment Marking

26. Procedure for selecting electrical equipment (IS 5571)
1. Collect the following information
a) Classification of Area as per Zone 0, 1, 2
b) The gases most likely to be present
c) The lowest ignition temperature of the gas /vapour involved
d) The temperature classification
e) The characteristic of gas vapor involved in relation to
minimum ignition energy or safe gap data for flame proof
enclosures
2. Select the type of protection based on area classification
3. Ensure that maximum surface temperature of electrical
equipment should not exceed ignition temp classified in IS
8239 and IS 2148)

27. Division Zone Ex Type of protection
1
0
Ex ia intrinsically safe
Ex s special (specially certified)
1
Any design suitable for zone 0 plus:
Ex d flameproof
Ex ib intrinsically safe
Ex p pressurized / continuous dilution
Ex e increased safety
Ex s special
Ex m encapsulation
2 2
Any design suitable for zone 1 plus:
Ex n or N non-sparking (non-incendive)
Ex o oil
Ex q powder / sand filled
Protection Techniques

28. Protection Techniques
‘i’ Intrinsically
Safe,
Intended to limit the ignition energy of the
equipment
ia = Zone 0
ib = Zone 1
“d” Flameproof
/ explosion
proof.
Apparatus to withstand and not pass to
outside; an internal explosion of flammable
mixture, which may originate inside
enclosure.
Class I,
Zone 1 or 2
“P” Purged and
Pressurized
Apparatus in which, the entry of flammable
mixture is prevented by maintaining air
pressure within the enclosure above
atmospheric pressure
Class I,
Zone 1 or 2
‘q’ Powder
filled
Apparatus that has alive parts embedded in
powdery material
Class I, Zone
1 or 2
‘o’ Oil
Immersion,
Apparatus that has alive parts embedded in
oil to a sufficient depth to prevent ignition
Class I, Zone
1 or 2

29. Protection Techniques
‘n’ Non sparking locations which under normal operation
are not capable of igniting a surrounding
explosive gas atmosphere and not likely to
create a fault that is capable of causing
ignition
for Class I,
Zone 2
‘e’ Increased
Safety
Increased security against excessive
temperatures and occurrence of arcs/
sparks.
for Class I,
Zone 2
‘s’ Hermetically
Sealed/Special
Enclosure is so designed that gases can’t
enter in it
‘m’ Encapsulation Arcing parts are completely surrounded in
a compound in such a way that an
explosive gas or vapor cannot be ignited
Class I, Zone 1
Zone 2

30. Explosion-protection methods / equipment -
Popular type
• Flameproof (Ex d)
• Increased Safety (Ex e )
• Non-Sparking (Ex n )
• Pressurization (Ex p )
• Intrinsically Safe (Ex i )
Ex
Few non popular type
• Powder filled Ex ‘q’ type
• Oil immersed Ex ‘o’ type
• Special Ex ‘s’ type

31. INGRESS PROTECTION (IP)
The IEC IP classification system designates the degree of protection
provided by an enclosure against impact and/or water or dust
penetration (ingress). It has two numbers; first—protection against
solid objects, second protection against water.
IP ratings do not indicate any degree of corrosion resistance.

32. INGRESS PROTECTION (IP)
FIRST NUMERAL
0 No protection
1 Objects greater than 50 mm
2 Objects greater than 12 mm
3 Objects greater than 2.5 mm
4 Objects greater than 1.0 mm
5 Dust - protected
6 Dust tight
SECOND NUMERAL
0 No protection
1 Vertically dripping
2 Angular dripping
3 Sprayed water
4 Splashed water
5 Water jets
6 Heavy seas
7 Effects of immersion
8 Indefinite immersion
IP X Y
Degree of Protection of persons against
contact with or moving parts inside
the enclosure & Protection of
Equipment against Solid ingress
Ingress of Liquid