The explosion properties of our fuel like gasses, vapors, combustible dusts have been studied and organized by their flammability limits and ignition temp etc in order to suitably assess the potential of an explosion and to take appropriate preventative measures to avoid an explosion.

1. Hazardous area – The fundamentals
of Hazardous Area Classification
Based on IEC Ex
Zones, Material Characteristics, Method of Determination of Hazardous Radius
Module-3 of 18

2. Hazardous Material – Characteristics
A flammable material is defined in IEC 60079-0 as follows:
A gas, vapor, liquid or solid that can react continuously with atmospheric oxygen and may therefore sustain fire or explosion
when such reaction is initiated by a suitable spark, flame or hot surface.
Flammable or combustible or Hazardous materials will ignite and continue to burn if exposed to a flame or source of
ignition.
Flammable Material can be divided into three subgroups:
• Flammable gases
• Flammable liquids/vapors
• Flammable solids
2

3. An explosion is defined as a sudden reaction involving rapid physical or chemical decay accompanied by an increase in
temperature or pressure or both.
What is Explosion
These three items are commonly referred to as ‘the fire or explosion triangle’.
FUEL
IGNITION
SOURCEOXYGEN
Explosion
For an explosion to occur, the following three
elements must be present:
Fuel (Combustible gas, vapor, mist or dust)
Oxygen
Ignition source
3

4. The Fuel
The explosion properties of our fuel (gasses, vapors, combustible dusts) have been studied and organized by their
flammability limits and ignition temp etc. in order to suitably assess the potential of an explosion and to take
appropriate preventative measures to avoid an explosion.
All flammable gasses, vapors and mists require to be mixed with oxygen to make them burn. There is about 20-21%
of oxygen in the air we breath. Mixtures of a flammable gas and certain percentages of air will burn if ignited.
The Fire Triangle shows the three necessary components required to support fire: Fuel, Oxygen and Ignition source.
All three elements must be present. What the triangle does not show is that both fuel and oxygen have to be mixed in
the relevant proportion in order to burn. The upper and lower concentrations of gas in atmospheric air, by volume,
are known as their flammability or explosive limit.
4

5. Flammable (Explosive) Range
This is the range between the lower explosive limit (LEL) and the upper explosive limit (UEL). Combustion will only occur if the
flammable mixture comprising fuel, in the form of a gas or vapor and air, is within certain limits.
No Combustion (Lack of
Oxygen
Between this limits is known as the Flammable
Range
No Combustion (Lack
of Fuel
5

6. Hazardous Material LEL (% Vol.) UEL (% Vol.)
Butane 1.6 8.4
Ethane 3.0 12.5
Ethyl Alcohol (Ethanol) 3.3 19.0
Gasoline (100 Octane) 1.4 7.6
Hydrogen 4.0 75.0
Methane 5.0 15.0
Methyl Alcohol (Methanol) 6.0 16.0
Acetylene 2.5 100 *
Propane 2.1 9.5
Toluene 1.1 7.1
Vinyl Chloride 3.6 33.0
Xylene 0.9 6.7
Flammable (Explosive) Ranges of various Hazardous Material
Hazardous Material – Characteristics
* Under special conditions
6

7. Hazardous Material Characteristics – Definitions
The Flash Point of a liquid is the lowest temperature of the liquid at which it gives off enough vapor to form an
ignitable mixture of vapor and air immediately above the liquid surface. FLASH POINT of a material gives an
indication of how readily that material will ignite in normal ambient temperature. The lower the flash point, the
greater the potential fire hazard. At this temperature the vapor may cease to burn when the source of ignition is
removed
The boiling point of a liquid is the temperature at which the vapor pressure of the
liquid equals the environmental pressure surrounding the liquid. A liquid in a vacuum
environment has a lower boiling point than when the liquid is at atmospheric
pressure. A liquid in a high pressure environment has a higher boiling point than
when the liquid is at atmospheric pressure. In other words, the boiling point of liquids
varies with and depends upon the surrounding environmental pressure.
The boiling point of a substance is the temperature at which it can change state from a
liquid to a gas throughout the bulk of the liquid
The Fire point is the minimum temperature at which a substance will continue to burn
without additional application of external heat.
7

8. Hazardous Material – Characteristics
Flammable liquid Flash Point
Ethanol (70%) 16.6 °C (61.9 °F)
Gasoline (petrol) −43 °C (−45 °F)
Diesel (2-D) >52 °C (126 °F)
Jet fuel (A/A-1) >38 °C (100 °F)
Kerosene >38–72 °C (100–162 °F)
Vegetable oil (canola) 327 °C (621 °F)
Biodiesel >130 °C (266 °F)
Flash Point of selected Flammable liquids
8

9. Hazardous Material – Characteristics
Boiling Points of selected Hazardous Material
Examples Boiling Points ( 0C)
Acetone 56.10
Ethanol (Ethyl Alcohol) 78.30
Gasoline 35 .00 to 200.00
Kerosene 154.40
Methanol (Methyl Alcohol) 64.80
Isopropyl Alcohol 82.80
Diesel 151.00 to 301.00
Xylene 138.90
9

10. Auto Ignition Temperature
The minimum temperature that will
initiate a self-sustained combustion
of liquid, gas or solid in the absence
of a spark or flame; the lower the
auto-ignition temperature, the
greater the fire hazard.
Dust and fibers are also defined in
terms of their ignition properties
including dust cloud ignition
properties. Both the cloud and layer
temperatures are to be taken into
consideration.
Hazardous Material Auto Ignition Temperature 0C
Gases
Hydrogen 585
Methane 538
Ethane 514
Liquids
Gasoline 245
Naphtha 288
Toluene 536
Dust
Cloud Temperature Layer Temperature
Coal Dust 380 225
Sugar 490 460
Flour 490 340
Hazardous Material – Characteristics
10

11. Hazardous Material – Characteristics
The vapor density is the ratio of the density of the gas
or vapor to the density of air (vapor density of air = 1).
Generally, vapors from flammable liquids are denser
than air and thus tend to sink to ground level where
they can spread over a large area.
Vapor Density
Hazardous Material Vapour Density
Ammonia 0.59
Ethylene 0.97
Hydrogen Sulfide 1.19
Trichloroethylene 4.50
Methylene Chloride 2.90
Benzene 2.70
Gasoline 4.40
11

12. Hazardous Material – Characteristics
Behavior of Hazardous Material when ignited
• At normal room temperatures, flammable liquids can give off enough vapor to form burnable mixtures with air. As a
result, they can be a serious fire hazard. Flammable liquid fires burn very fast.
• They also give off a lot of heat and often clouds of thick, black, toxic smoke.
• Combustible liquids at temperatures above their flashpoint also release enough vapor to form burnable mixtures with air.
Note: flammable liquids have a flashpoint below 37.8°C (100°F). Combustible liquids have a flashpoint at or above 37.8°C (100°F) and below 93.3°C (200°F)
• Hot combustible liquids can be as serious a fire hazard as flammable liquids.
• Spray mists of flammable and combustible liquids in air may burn at any temperature if an ignition source is present.
• The vapors of flammable and combustible liquids are usually invisible. They can be hard to detect unless special
instruments are used.
• Most flammable and combustible liquids flow easily.
• A small spill can cover a large area of workbench or floor. Burning liquids can flow under doors, down stairs and even into
neighboring buildings, spreading fire widely.
• Materials like wood, cardboard and cloth can easily absorb flammable and combustible liquids.
• Even after a spill has been cleaned up, a dangerous amount of liquid could still remain in surrounding materials or
clothing, giving off hazardous vapors.
12

13. Hazardous Area
Classification?
13

14. Hazardous Area Classification?
To prevent any risk of explosion or fire and improve safety of the process and employees, all potential hazardous areas
must be classified according to the processes conducted in these areas. It is in responsibility of the end user to define the
Hazardous Areas within the operations.
Hazardous Area classification is the method of analyzing and classifying the environment where explosive gas
atmospheres may occur and also to facilitate the proper selection of the electrical equipment. The concept of assessing
the potentially explosive areas is crucial to limiting the risk associated with the installation of electrical equipment in
potentially explosive environment.
Appropriate areas classification allows preparation of safety procedures for plant operation and maintenance.
Classification varies across the world.
14

15. Hazardous Area Classification?
In countries that have adopted the IEC (International Electrotechnical Commission) philosophy this is referred to as Zoning
whilst in North American installations are classified by Classes, Divisions and Groups to ascertain the level of safety
required.
Hazardous Area classification as per IEC 60079
Zone Classification The boundary of a particular zone of hazardous area is mainly determined by both chemical and
physical parameters, such as the release rate of gas or vapor and duration of release in normal condition [2]. There
are three types of zones namely zone 0, zone 1 and zone 2 can be present in any explosive atmosphere as per
IS 5572:2009 and IEC 60079-10
15

16. Hazardous Area Classification?
Areas where there is the likelihood of the presence of gases and vapors and dusts and fibers are referred to as zones.
The higher the number in this ‘zonal classification’ the smaller is the risk of an explosion.
Zones are classified as per IEC 60079 and ATEX are shown below :
Gases and Vapors Dusts and Fibers
Zone 0 Zone 1 Zone 2 Zone 20 Zone 21 Zone 22
Hazardous Area classification as per IEC 60079 and ATEX
Zones classified as per IEC 60079 and ATEX
16

17. What type of Hazardous Area Classifications
and Protections does your Company use?
What type of Hazardous Substances
may be present?
What type of Hazardous Substances
may be present?
Class I
Gas & Vapors
Class II
Dust
Class III
Fibers & Flying
Zones 0,1,2
Gases & Vapors
Zones 20, 21, 22
Dust
How often Hazardous Substances
may be present?
How Often Hazardous Substances
May be Present?
Are likely to exist under
normal operating
conditions
Are not likely to exist
under normal operating
conditions
Are likely to exist
under normal
operating conditions
Continuously present
for long periods of
time under normal
operating conditions
Are not likely to
exist under normal
operating conditions
Division 1 Division 2 Zone 2: Gases &
Vapors -Zone 22: Dust
Zone 1: Gases & Vapors
Zone 21:Dust
Zone 0: Gases & Vapors
Zone 20:Dust
NEC / CEC Standards ATEX / IECEx Standards
Comparing Classes/Division System with Zone System
17

18. Hazardous Area Classification-Zones and Divisions
Duration and presence of hazards compared
to risk (Division)
￮ Zone 0 classified locations: An area where ignitable
concentrations of flammable gases, vapors or liquids are
present continuously or for long periods of time under normal
operating conditions. An example of this would be the vapor
space above the liquid in the top of a tank or drum. The
ANSI/NEC classification method consider this environment a
Class I, Division 1 area. As a guide for Zone 0, this can be
defined as over 1000 hours/year or >10% of the time.
￮ Zone 1 classified location -An area where ignitable
concentrations of flammable gases, vapors or liquids are likely
to exist under normal operating conditions. As a guide for
Zone 1, this can be defined as 10–1000 hours/year or 0.1–
10% of the time.
￮ Zone 2 classified locations: An area where ignitable
concentrations of flammable gases, vapors or liquids are not
likely to exist under normal operating conditions. In this area
the gas, vapor or liquids would only be present under
abnormal conditions (most often leaks under abnormal
conditions). As a general guide for Zone 2, unwanted
substances should only be present under 10 hours/year or 0–
0.1% of the time. 18

19. Video: Hazardous Locations Training
This Video Covers:
1. Combustion Fundamentals
2. Fire & Explosion Requirements
3. Explosive Limits
4. Auto ignition & Flash Point
5. Explosive group
6. IEC Classification
7. Temperature Classification
19

20. Hazard radii may be determined by either:
 Direct examples limited to common facilities given or
 A point source method, or
 A risk based method for secondary grade release equipment or when the
release rate (hole size and pressure) is unknown (IP Code, Part 15).
Hazard radii depend on the following parameters:
 The grade of release
 The fluid category
 The release pressure
 The hole release size
Determination of the Hazard Radii
20

21. Determination of the Hazard Radius
Hazard radii (R1) are given using dispersion calculation methodology applied to particular fluid compositions; however, a
more accurate value of hazard radius may be determined using dispersion models which take into consideration all the actual
physical properties of the gas, characteristics of the environment and conditions of release.
Gas dispersion calculations/models, if necessary, shall be carried out, using software such as PHAST.
An atmospheric dispersion model is a:
• Mathematical simulation of the physics and chemistry governing the transport, dispersion and transformation
of pollutants in the atmosphere.
• Means of estimating downwind air pollution concentrations given information about the pollutant emissions
and nature of the atmosphere.
21

22. Dispersion Modelling to determine Hazardous Area Radius
Dispersion models can take many forms. The simplest are
provided in the form of graphs, tables or formulae on paper.
Today dispersion models more commonly take the form of
computer programs, with user-friendly interfaces and online
help facilities for example PHAST.
PHAST Predicted Gas Dispersion Results Showing Gas Cloud Side
View (Top) and Footprint (Bottom) for three (3) pre-determined
concentrations.
PHAST has the ability to simulate the progress of a potential
incident from the initial release to far-field dispersion including
modeling of pool spreading and evaporation, and flammable
and toxic effects including explosions and fires.
PHAST examines the progress of a potential incident from the
initial release to far-field dispersion analysis including modeling
of pool spreading and evaporation, and flammable and toxic
effects. 22

23. Thanks! We also have a 5-Day
comprehensive program.
Any questions?
You can find me at
￮ aniruddha@siteselfies.com
￮ aniruddha_k20@hotmail.com
￮ statsengineering@gmail.com
￮ Call:+91-9820281156
Zones, Material Characteristics, Method of Determination of Hazardous Radius
23