This document is the introduction chapter of "The Practical Guide to Hazardous Area Classification" by Abhisam Software. It defines hazardous areas as industrial workplaces that produce, process, handle or store potentially explosive materials. It notes that hazardous areas are not limited to chemical plants, but can include places like grain silos, flour mills, coal mines, oil tankers, refineries, gas power plants and gas stations. The introduction stresses that proper area classification and safety engineering practices are needed to reduce the risk of fires and explosions in these hazardous locations.

1. The Practical Guide to Hazardous Area Classification
By Abhisam Software
© Copyright 2009-2010 Abhisam Software. All rights reserved.
1

2. The Practical Guide to Hazardous Area Classification
STOP! DID YOU PAY FOR THIS EBOOK?
YOU COULD HAVE GOT IT FREE IF YOU HAD
PURCHASED THE HAZARDOUS AREA
INSTRUMENTATION COURSE.
IT IS STILL NOT TOO LATE NOW !
IF YOU WOULD LIKE TO OWN THIS EBOOK FREE,
PLEASE DOWNLOAD THE
HAZARDOUS AREA INSTRUMENTATION COURSE
Please send an email along with your proof of purchase of this book, to
sales@bin95.com to get the coupon code to get a credit of $17 that you have paid for
this book, when you order the HAZARDOUS AREA INSTRUMENTATION e-learning
course from http://www.bin95.com/ebooks/hazardous_area_instrumentation.htm
2

3. The Practical Guide to Hazardous Area Classification
Copyright Information
© 2009-2010 Abhisam Software. All Rights reserved. No part of this publication
may be reproduced or transmitted in any form or by any means, mechanical or
electronic, including photocopying or recording, or by any information storage
and retrieval system, or transmitted by email without permission in writing from
the author and publisher.
Published By
Abhisam Software,
First Edition -2009
Second Edition -2010
www.abhisam.com
3

4. The Practical Guide to Hazardous Area Classification
Disclaimer: Nothing that is stated or construed by reading the contents of this book can be
claimed to be safety advice in the legal sense. You are urged to refer to your own local
regulations, national and international standards for the exact regulations that may apply to
you. This guide book is to make the task of understanding the various codes and standards,
much easier and to give you broad guidelines and a roadmap to help your plant or facility
become a better and safer place. While all attempts have been made to verify the information
provided in this publication, neither the author nor the publisher assumes any responsibility
for errors, omissions, or contrary interpretations of the subject matter herein. The publisher
wants to stress that the information contained herein may be subject to varying international,
federal, state, and/or local laws or regulations. The purchaser or reader of this publication
assumes responsibility for the use of these materials and information. Adherence to all
applicable laws and regulations, including international, federal, state and local governing
professional licensing, business practices, advertising, and all other aspects of doing
business in the EU, US, Canada or any other jurisdiction is the sole responsibility of the
purchaser or reader. Neither the author nor the publisher assume any responsibility or liability
whatsoever on the behalf of the purchaser or reader of these materials. While due care has
been taken to review and verify the accuracy, reliability and correctness of the contents of this
ebook, the publishers are not liable for any direct or indirect or consequential or any other
kind of damage, which may result from using this ebook and the contents therein.
4

5. The Practical Guide to Hazardous Area Classification
TABLE OF CONTENTS
Chapter 1 Introduction
Introduction to Hazardous Areas
Why do we classify Hazardous Areas?
Chapter 2 Basic Concepts
What is a Hazard?
What is Risk?
Can we avoid risk altogether?
Area Classification - A measure of risk
Area Classification Benefits
How does Area Classification work?
How can Area Classification reduce costs?
Chapter 3 Fire & Explosion Fundamentals
Fire
Flammable or Hazardous Material
Fire Triangle
What is an Explosion?
Properties of Hazardous Materials
LEL & UEL
Flash Point
Fire Point
Auto-ignition
Combustible dusts
Dust Explosions - Five necessary Factors
Chapter 4 Fundamental Ideas about Area Classification
Chapter 5 Standards for Area Classification
5

6. The Practical Guide to Hazardous Area Classification
European System / IEC System
Zones
Groups
American System (NEC)
Classes
Divisions
Chapter 6 Standards for Classification of Explosive Dusts
IEC System
North American System
Chapter 7 Material Classification
IEC System
North American System
Chapter 8 Temperature Classification
IEC System
Example of Temperature Classification
North American System
Chapter 9 Some other important Standard Guidelines
ATEX Guidelines
ATEX Marking System
Equipment Group
Equipment Category
Substance Group
Chapter 10 IEC Ex-Unification of the two Systems
Chapter 11 How to carry out Area Classification
Area Classification Myths
Myth 1
Myth 2
6

7. The Practical Guide to Hazardous Area Classification
Myth 3
Myth 4
Sources of release
Relations of Grade with Zones
Ventilation Considerations
Step by step guide to Area Classification
Chapter 12 Practical Study of an Area Classification Exercise
Chapter 13 Consequences of poor Area Classification
Over Classification - A white elephant
Under Classification - Playing with Fire
So now, what do we do?
Example 1
Example 2
Example 3
Example 4
Example 5
7

8. The Practical Guide to Hazardous Area Classification
Introduction to hazardous areas
Many industrial work places produce, process, handle and store materials which
are potentially explosive and thus hazardous in nature. The risk of fire or
explosion while handling these materials is high. But it is not just the chemical or
petrochemical industries that we are talking about here.
Surprised? You should not be really. Grain storage silos, processing plants that
handle large amounts of powders (including flour milling units), coal mining and
handling plants, large oil supertankers, all handle materials, that could possibly
lead to fires and explosions. Other typical examples, include offshore and
onshore oil & gas production platforms, oil refineries, ships carrying chemical
containers, storage terminals at ports, large tank farms, pulp & paper industries,
industrial warehouses, gas based power plants and even gasoline filling stations.
Potentially explosive atmospheres, need not be generated in only these
obviously hazardous areas. A location which looks innocuous enough, like a
grain silo can also be classified as a hazardous area, because grain dust can
also be explosive. In fact, dust explosions can sometimes be more severe than
even gas or vapor explosions. Therefore grain elevators & associated equipment
like bucket elevators and conveyors carrying grain, which have a large amount of
grain dust are also classified as hazardous areas. Similar powder processing
plants like those handling coal dust, flour or cotton fibers can also be classified
as hazardous (dust) locations.
These areas are prone to risk of fires and explosions due to the nature of the
materials handled and hence need a different approach than other “normal”
areas. If proper area classification and safety engineering practices are followed
while working in these areas, we can greatly reduce the risk of fire and explosion
hazards in these places. This “practical” guide book is meant to be used as the
name suggests-to get a working idea of how hazardous area classification works,
8

9. The Practical Guide to Hazardous Area Classification
how you can use it to your advantage, by reducing the costs of compliance-but
without compromising in any way, on the actual safety of your plant.
It is intended for all those people who are involved in working in hazardous areas,
whether as a plant engineer, or instrument technician or a safety supervisor. It
should be noted that this book does not contain complicated math or partial
differential equations (that may induce sleep in the best of practising engineers).
Why do we classify hazardous areas?
This is the first fundamental question that begs an answer. Why do we classify
areas and the materials present in these areas and call them “hazardous”? The
reason is, that general purpose electrical equipment, like motors or lamps,
cannot be used in these areas without having some kind of protection against
accidental ignition. Nor can we use general purpose electrical or electronic
instruments like transmitters or local indicators. This is because all electrical
equipment can produce energy in the form of sparks, which can ignite these
hazardous materials and /or cause explosions, thereby causing catastrophic
damage.
Hence, in hazardous areas we use special purpose, “explosion protected”
electrical equipment and instruments.
Note that the mere presence of flammable materials or explosive dusts in an
area, does not immediately mean that the risk of fire or explosion is high. The
flammable vapor or gas, has to be a part of a mixture with air, which can then
easily ignite or explode, if some more conditions are met. Since these conditions
are not uniformly present throughout a place that handles these materials, we
have the concept of classification.
It is to be noted that “hazardous area classification” is to be done for areas of the
plant that would have instances of flammable mixtures of vapors, gases or dusts
9

10. The Practical Guide to Hazardous Area Classification
in the day to day operations. Under unusual conditions like a catastrophic
accidental release of a large quantity of inflammable vapors for example, this is
not applicable, as such situations are not easily predictable. Under the usual day
to day operational conditions in a plant or facility, there are some areas, which
would have the presence of flammable mixtures of vapors, gases or dusts. Thus,
the vapor space in a storage tank, the area around a mechanical seal of a pump
or agitator, the area surrounding a breather valve on a storage tank (that
contains flammable liquids), are all hazardous areas, which need to be classified.
We classify some areas as “more prone” to the risk of fire and or explosion and
others as “less prone”. We may find some areas, that are not at all prone to any
kind of fire or explosion, except in the rarest of circumstances. For example, if an
industrial facility has large open spaces and the office building is located several
hundred meters away from the plant that actually processes the hazardous
materials, then the chance of an explosion occurring in the office block, is very
less (assuming some other conditions that will be explained later).
How we do this segregation and classification in a structured manner, will be the
main subject of this book, area classification.
Before we jump headlong into area classification, let us understand some basic
concepts first.
10

11. The Practical Guide to Hazardous Area Classification
Basic Concepts
What is a hazard?
A hazard is an inherent attribute or feature of a material, that can cause harm to
equipment, people or the environment. An example of a hazard is a large
quantity of flammable gas stored at a high pressure in a tank. Thus a plant
having a large quantity of a flammable gas stored in a tank, as shown in the
picture below, is an example of a hazard.
Fig 1: A Hazard
What is Risk?
Risk is the measure of the likelihood, that the undesired event or accident will
actually occur. Thus if a plant stores a large quantity of flammable gas as
described above, but has a lot of safety systems in place to ensure that the gas
does not leak, ignite or explode, or cause an accident in other ways, then the
likelihood of an accident happening, is very less, therefore, one can say that the
risk is low. Risk is also dependent on the severity of the consequences. The
severity of the consequence means in simple words “how bad”. For example how
bad will it be if a large storage tank of Acetone, a highly volatile and inflammable
11

12. The Practical Guide to Hazardous Area Classification
liquid explodes? The extent of the damage is what we mean by the words
“severity of the consequence”
Thus Risk= (Probability of Occurrence) X (Severity of Consequence).
Consequence)
The severity of consequences, for fires and explosions in hazardous areas is
very high, as all of us know. Therefore in the above equation, if we want to
reduce the risk, we can only reduce the probability of occurrence, since we have
almost no control over the severity of the occurrence. By classifying hazardous
areas, we intend to reduce the probability of occurrence and thus reduce the risk.
Can we avoid risk altogether?
It is not possible to exist in a world without some amount of risk. Many people
know that driving a car is riskier than flying in an airplane, however, do you know
that staying at home also entails a risk? It is certainly not zero.
Since we cannot avoid risk, we then manage it in a logical way. We do this
unconsciously in our day-to-day activities, without realizing it. For example, to
reduce the risk of getting knocked down by a car, while crossing a busy street,
we reduce the risk by crossing it only at a pedestrian crossing, when the traffic
signal turns green (for pedestrians) and also by watching out for speeding cars.
Notice that here also, we cannot reduce the severity of the consequence. The
severity of the consequence of getting knocked down by a speeding car could
entail death, or disability or at least a severe injury. Since we have no control
over the severity of the consequence, we reduce the other factor in the risk
equation, which is the probability of the occurrence.
In the same way, we manage the risk of handling and storing large amounts of
flammable and explosive materials by area classification, which reduces the
probability of the materials catching fire or exploding.
12

13. The Practical Guide to Hazardous Area Classification
Hazardous Area Classification- A measure of risk
Hazardous Area classification tries to give a profile of the risk of explosion in
these areas. It cannot predict definitively, that an explosion will or will not take
place in that area. It only segregates areas into areas where the likelihood of an
explosion is more and areas where the likelihood is low or improbable. The
classification provides us a tool to mitigate the risk of explosion in such areas.
Area Classification-What are the benefits?
If properly carried out, an area classification can
a) Give us a risk profile of the plant or facility, to enable us to operate it safer.
This enables top management to really understand the real risk of the
facility and then come up with appropriate strategies to mitigate this risk.
b) Enable us to design and install electrical, instrumentation and control
system equipment that will not cause fires or explosions, at an optimum
cost.
c) Reduce the costs of compliance to regulations and standards without
compromising on the safety.
d) Make the overall operations safer and more profitable.
How does Area Classification work?
By properly and judiciously designating certain areas of the plant or facility, as
hazardous (with its subdivisions of Zone 0,1 and 2 or Division 1 and Division 2)
we can know which areas of the plant are more hazardous (and need special
attention or equipment) and which are less hazardous. We can also know which
areas are safe (well, almost). This gives a proper risk profile to the top
management
13

14. The Practical Guide to Hazardous Area Classification
------------------------------------------END OF PREVIEW---------------------------------------
To get the full ebook, please visit the following link
http://www.bin95.com/ebooks/hazardous_area_classification.htm
14