FAQs

The purpose of the Hazardous Area Classification study is to determine the extent of the 
hazardous areas around equipment handling or storing flammable fluids, combustible fluids and 
combustible dusts, both liquid and vapors in terms of Zone 0/20, Zone 1/21, Zone 2/22 
The aim of hazardous area classification is to avoid ignition of those releases that may occur from 
time to time in the operation of facilities handling flammable liquids and vapors.  The approach is 
to reduce to an acceptable minimum level the probability of coincidence of a flammable 
atmosphere and an electrical or other source of ignition occurring. In Hazardous Area 
Classification the extent of the hazardous areas around equipment handling or storing flammable 
fluids, both liquid and vapors is determined in terms of Zone 0, Zone 1, and Zone 2. The hazardous 
area classification around the equipment handling flammable/explosive dust is determined in 
terms of Zone 20, Zone 21, and Zone 22. 

The Scope of HAC is as follows: – 
The Hazardous area classification is carried out as per:  
∙Classification of the Hazardous area for explosive dust is carried out as per IEC 60079-10-2  
∙Classification of the Hazardous area for flammable liquids/ gases/ vapors is carried out as per 
IEC 60079-10-1 

 The reference used for HAC study is as follows: 
∙Draft Version of EI15 Edition 4– Model Code of Safe Practice – Area Classification Code for 
Installations Handling Flammable Fluids. Energy Institute 2015. 3. 
∙ EI15 Edition 3– Model Code of Safe Practice – Area Classification Code for Installations 
Handling Flammable Fluids. Energy Institute 2005. 
∙IEC 60079-10-1 Explosive atmospheres Part 10-1: Classification of areas – Explosive gas 
atmospheres 
∙IEC 60079-10-2 Explosive atmospheres Part 10-2: Classification of areas – Explosive dust 
atmospheres 
∙Any other National and International Guideline Recommended by Client. 

The order of precedence for HAC study is as follows: 
∙IEC 60079-10-1 Explosive atmospheres Part 10-1: Classification of areas – Explosive gas 
atmospheres 
∙IEC 60079-10-2 Explosive atmospheres Part 10-2: Classification of areas – Explosive dust 
atmospheres 
∙Draft Version of EI15 Edition 4– Model Code of Safe Practice – Area Classification Code for 
Installations Handling Flammable Fluids. Energy Institute 2015. 3. 
∙ EI15 Edition 3– Model Code of Safe Practice – Area Classification Code for Installations 
Handling Flammable Fluids. Energy Institute 2005. 
UAE regulation 
∙National & International reference books. 

 The methodology for HAC Study is as follows: 
∙Data collection 
∙MSDS Sheet Preparation 
∙Process step and Representative Chemical sheet preparation  
∙Client Approval for HAC Schedule preparation  
∙HAC Schedule 
∙Draft Report 
∙Client Approval for HAC marking  
∙HAC marking  
∙Comments incorporation along with CRS (Comment Resolution Sheet)  
∙Final Report 

Three types of grades of release are as follows 
∙Continuous Grade release (C): A release that is continuous or nearly so, or that occurs 
frequently and for short periods. 
∙Primary Grade release (P): A release that is likely to occur periodically or occasionally in 
normal operation, that is, a release which, in operative procedures, is anticipated to occur. 
∙Secondary grade release (S): A release that is unlikely to occur in normal operation and, in any 
event, will do so only infrequently and for short periods, that is, a release which, in operating 
procedures, is not anticipated to occur. 

Three types of class of fluid are as follows:  
Flammable Liquids vary in volatility and have a flash point below 93 °C and a Vapor Pressure not 
exceeding 2.81 kg/cm2 at 37.8 °C. These are divided into three classes, as follows, 
∙Class A :  Flammable liquids having flash point below 23 °C 
∙Class B :  Flammable liquids having flash point 23 °C and above but below 65 °C  
∙Class C :  Flammable liquids having flash point 65 °C and above but below 93 °C 

 The steps for HAC Study are as follows: 
∙Identification of the Point Source or Source of Release 
∙Determine the Grade of Release 
∙Determine the Class of the Fluid 
∙Determine the Ventilation Requirements 
∙Establish Zone Classification 
∙Determine Hazard Radii 
∙Determine Hazardous Area 
To enable selection of electrical equipment’s appropriate to the zone classification, the 
apparatus sub group and temperature class is then determined based on the flammable 
substances that can be released. 

Following degree of dilution is recognized in HAC Study as per IEC Guidelines.  
The following three degrees of dilution are recognized: 
∙High dilution (H): The concentration near the source of release reduces quickly and there will 
be virtually no persistence after the release has stopped. 
∙Medium dilution (M): The concentration is controlled resulting in a stable zone boundary, whilst 
the release is in progress and the explosive gas atmosphere does not persist unduly after the 
release has stopped. 
∙Low dilution (L): There is significant concentration whilst release is in progress and/or significant 
persistence of a flammable atmosphere after the release has stopped. 

Different Zones defined by IEC for hazardous areas are follows:  
IEC defines zones based on the frequency and duration of the presence of hazardous 
substances. Zones include Zone 0 (continuous presence), Zone 1 (intermittent presence), and 
Zone 2 (occasional presence) for gases and vapors, and Zone 20 (continuous presence), Zone 21 
(intermittent presence), and Zone 22 (occasional presence) for combustible dusts. 
∙Zone 0 Areas: An area in which an explosive gas atmosphere is present continuously or is 
present for long periods. Examples are vapor space above closed process vessels, storage 
tanks or closed containers, areas containing open tanks of volatile, flammable liquid. 
∙Zone 1 Areas: An area in which an explosive gas atmosphere is likely to occur in normal 
operation 
∙Zone 2 Areas: An area in which an explosive gas atmosphere is not likely to occur in normal 
operation and if it does occur it will exist for a short period only 
∙Zone 20: A place in which an explosive atmosphere, in the form of a cloud of combustible dust 
in air, is present continuously, or for long periods or frequently for short periods 
∙Zone 21: A place in which an explosive atmosphere, in the form of a cloud of combustible dust 
in air, is likely to occur occasionally in normal operation. 
∙Zone 22: A place in which an explosive atmosphere, in the form of a cloud of combustible dust 
in air, is not likely to occur in normal operation but, if it does occur, will persist for a short period 
only. 

 The documents required for the HAC Study include the following: 
∙Scope of work 
∙Approved P&IDs 
∙List of Chemicals 
∙Process design basis 
∙Hazardous inventories and their SDS 
∙Process description 
∙MSDS or Chemical properties of RM & FG 
∙Equipment Design and Operating Condition /MOC  
∙Equipments & Details 
∙Layout & plot plan 
 

The availability of ventilation plays a crucial role in the presence or formation of an explosive 
gas atmosphere, thus affecting the classification of hazardous zones. Three levels of ventilation 
availability are considered: 
∙Good (G): Ventilation is continuously present. 
∙Fair (F): Ventilation is expected during normal operation, with occasional short discontinuities. 
∙Poor (P): Ventilation does not meet the standards of fair or good, but long periods of 
discontinuities are not expected. 

The documents deliverables for HAC Study are as follows: 
∙Executive Summary 
∙Document Review 
∙Submission of terms of reference 
∙HAC Methodology 
∙HAC Schedule 
∙HAC Marked Layout  
∙Comments Resolution sheets 
∙Reference 
∙List of tables 
∙List of appendix 

Following industrial sectors require HAC 
Common sectors include oil and gas, chemical processing, pharmaceuticals, food and 
beverage, mining, and manufacturing where the presence of flammable or combustible 
substances poses a risk of ignition and explosion. 

 Following software will be used for HAC marking: 
∙AutoCAD 

Different guidelines used for HAC study are as follows:  
∙NFPA-497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) 
Locations for Electrical Installations in Chemical Process Areas. 
∙NFPA–499 (Classification of Combustible Dusts and of Hazardous (Classified) Locations for 
Electrical Installations in Chemical Process Areas) 
∙Classification of the Hazardous area for explosive dust is carried out as per IS 61241 
∙Classification of the Hazardous area for flammable liquids/ gases/ vapors is carried out by IS 
5572   

Inadequate HAC Study can lead to following consequences 
Inadequate classification may lead to increased risk of ignition and explosion, equipment failure, 
injury to personnel, damage to property, environmental pollution, and legal liabilities, 
underscoring the importance of following IEC guidelines for hazardous area classification. 
 

The objective of HAZOP is as follows: –
The purpose of HAZOP Study is to identify the hazard and operability problems and to reduce the probability and consequences of an incident in the process facilities that would have a detrimental impact to the personnel, plant, properties, environment and company reputation.
 

The Scope of HAZOP is as follows:-
HAZOP studies shall be applied to all new, continuous process designs, including package units & utility systems. However, the applicability of HAZOP during the various life cycle phases of the system is described below as per IEC 61882 STD:-
Conceptual Design phase – In this phase, the design concept and major system components are decided, but the design and documentation to conduct the HAZOP do not exist.
Front End Engineering Design (FEED) phase – During this phase, the design is developed, methods of operation are decided and documentation is prepared.
Detail Design / Engineering Phase – HAZOP Study during this phase shall be conducted after finalizing the detailed design, before the issue of important engineering drawings and documentation including P & IDs, C&E etc.,
Installation and Commissioning Phase – In case where the proper operation sequences and instructions are critical and the commissioning and operation of the system can be hazardous
Operational Phase- HAZOP Study shall be considered during Operational Phase before implementing any changes to the existing system

The commonly used reference for HAZOP studies is as follows:
IEC 61882: 2016 Hazard and Operability Studies (HAZOP Studies) Application Guide

The commonly used order of precedence for HAZOP studies is as follows:
IEC 61882: 2016 Hazard and Operability Studies (HAZOP Studies) Application Guide,
As per Client Guidelines and
National & International reference books.

The methodology for HAZOP Study is as follows:-
Data collection
Pre-HAZOP Workshop Preparation
HAZOP Workshop / Site visit
Draft Report
Comments incorporation along with CRS (Comment Resolution Sheet)
Final Report

The steps for the Pre-HAZOP Workshop Preparation are as follows:-
Gather Information
MSDS Sheet Preparation
Node Marking on P&ID
Client Approval for Node Marking
Discussion with Client
Worksheet Preparation

The documents required for the HAZOP Study include the following:
Scope of work
Approved P&IDs
Process design basis
Approved PFDs
Approved Cause & Effect Diagram
Operating & Control Philosophy Document
Hazardous inventories and their SDS
Process description
MSDS or Chemical properties of RM &FG
Safety Test Report
Previous HAZOP Report
Equipment Design and Operating Condition /MOC

The steps for conducting a HAZOP Study are outlined below:
Select a Node, which contains an elementary unit of the plant.
Define the Node design intent and process conditions.
Apply the first parameter to the node such as Flow, Pressure, Temperature, Level, Composition, etc.
Apply suitable Guide Word such as more, less, etc. to obtain a Deviation of the Parameter.
Identify the potential and credible Causes associated with the Deviation by brainstorming.
Assess the Consequences of each cause.
Identify Safeguards included in the design to prevent and/or mitigate the hazard.
Agree a Recommendation for action if the existing safeguards are found to be inadequate. If an immediate solution is available and acceptable to the team, the modification is recorded in the HAZOP worksheet and HAZOP master P&ID will be marked up accordingly. Where solutions are unlikely to be derived without a technical evaluation, the Chairman will refer the problem for separate assessment.
Repeat the above procedures to the next guideword (move to step 4) until these guidewords have been completed.
Repeat the above procedures to the next parameter (move to step 3) until these parameters have been completed.
Move to the next node (go step 1) of the process system. All process systems will be examined

The document deliverables for the HAZOP Study are as follows:
Executive Summary
Document Review
Submission of terms of reference
HAZOP Methodology
Risk Ranking Matrix
Participant Attendance sheet
Node List
Executive Summary
HAZOP Worksheet
Comments Resolving sheets
Mark Up P&ID’s
Reference
List of tables
List of appendix

The Fundamental Assumption for the HAZOP Study are as follows:
The potential for hazard and operability problems does not exist when the process is operating within its design envelope.
Cause shall be in the same node; consequences can be anywhere in the process.
Everything is running well and then “SOMETHING” happens

The software to be used for the HAZOP study is as follows:
PHA Pro version 8.19 software.
 

The Exclusion for the HAZOP study is as follows:
Simultaneous occurrence of two unrelated incidents
Operator’s negligence(Except common human error)
Simultaneous failure of more than one independent protective device
Natural calamity( Flood, Earthquake) except where it is design case
External fire/escalation

The Consideration Of Safeguards for the HAZOP study is as follows:
Following is deemed as protection/safeguard
Interlock/ Shutdown system/ Trip
Alarm system for operator action
Sample monitoring system
Mechanical monitoring device
Operating instructions and operating manual
Indicator and status signal gauges when the associated system in operator

The definition of study node is as follows:
The Node is the portion of the plant subject to the study, where single or limited process
functions are assigned.

The definition of parameters in HAZOP Study is as follows:
The usual parameters applied to all nodes are Pressure, Temperature and Composition. Additional parameters are Flow, Level, etc. These additional parameters may be required by the nature of each node.

The definition of guidewords in HAZOP Study is as follows:
The Guidewords, such as More, Less, Reverse and Other Than, are combined with Parameters, Flow, Temperature and Pressure to derive meaningful deviations.

The meaning of deviation in HAZOP Study is as follows:
Deviations consist of a GUIDEWORD + PARAMETER

The information which are typically included in Executive summary is as follows:
The executive summary of a HAZOP (Hazard and Operability Study) Report provides a overview of the study’s objectives, methodology, key findings, and recommendations.
It typically includes:
Introduction: Briefly outlines the purpose of the HAZOP study and the systems/processes analyzed.
Methodology: Describes the approach used in the study, including the team composition, brainstorming sessions, and node identification.
Key Findings: Summarizes the significant deviations or hazards identified during the study, along with their potential consequences.
Recommendations: Provides high-level recommendations for mitigating the identified hazards and improving the safety and operability of the system.
Conclusion: Concludes with a summary of the overall importance of the study and any next steps.

Recommendations are classified as follows:
Recommendations in HAZOP (Hazard and Operability Study) are typically classified based on their urgency, impact, and status. Here are the common classifications:
Category A: Urgent Actions- Recommendations that require immediate attention and should be implemented before the system is commissioned or operated. These actions are critical for preventing severe consequences or hazards.
Category B: Important Actions- Recommendations that are important for safety or operability but can be implemented after the system is commissioned. These actions should be completed within a specified timeframe to mitigate risks effectively.
Category C: General Improvements- Recommendations that focus on enhancing overall plant performance, efficiency, or reliability. These actions typically have no immediate safety implications but contribute to long-term improvements.
Category D: Pending Actions- Recommendations for which a final decision or conclusion is pending. These actions may require further evaluation or discussion before being classified as Category A or B recommendations.

The format used for Recommendation Table and legends is as follows:

The format used for HAZOP Worksheet is as follows:

The meaning of Comment Resolution Sheet (CRS) is as follows:
A comment resolution sheet is a document used to track and address comments, feedback, or issues raised during a review process, audit, or evaluation.

The objective of HAC is as follows:
The purpose of the Hazardous Area Classification study is to determine the extent of the hazardous areas around equipment handling or storing flammable fluids, combustible fluids and combustible dusts, both liquid and vapors in terms of Zone 0, Zone 1, Zone 2 and Division 1 and Division 2
The aim of hazardous area classification is to avoid ignition of those releases that may occur from time to time in the operation of facilities handling flammable liquids and vapors.  The approach is to reduce to an acceptable minimum level the probability of coincidence of a flammable atmosphere and an electrical or other source of ignition occurring. In Hazardous Area Classification the extent of the hazardous areas around equipment handling or storing flammable fluids, both liquid and vapors is determined in terms of Zone 0, Zone 1, and Zone 2. The hazardous area classification around the equipment handling flammable/explosive dust is determined in terms of Division 1, Division 2.

The Scope of HAC is as follows: –
The Hazardous area classification is carried out as per:
Classification of the Hazardous area for explosive dust is carried out as per NFPA 499
Classification of the Hazardous area for flammable liquids/ gases/ vapors is carried out by NFPA 497

The reference used for HAC study is as follows:
NFPA-497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.
NFPA–499 (Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas)

The order of precedence for HAC study is as follows:
NFPA 497/ NFPA 499
As per Client Guidelines
Other international standards

The methodology for HAC Study is as follows:
Data collection
MSDS Sheet Preparation
Process step and Representative Chemical sheet preparation
Client Approval for HAC Schedule preparation
HAC Schedule
Draft Report
Client Approval for HAC marking
HAC marking
Comments incorporation along with CRS (Comment Resolution Sheet)
Final Report

Three types of grade of release are as follows:
Continuous Grade release (C): A release that is continuous or nearly so, or that occurs frequently and for short periods.
Primary Grade release (P): A release that is likely to occur periodically or occasionally in normal operation, that is, a release which, in operative procedures, is anticipated to occur.
Secondary grade release (S): A release that is unlikely to occur in normal operation and, in any event, will do so only infrequently and for short periods, that is, a release which, in operating procedures, is not anticipated to occur.

Three types of class of fluid are as follows:
Flammable Liquids vary in volatility and have a flash point below 93 °C and a Vapor Pressure not exceeding 2.81 kg/cm2 at 37.8 °C. These are divided into three classes, as follows,
Class A       :  Flammable liquids having flash point below 23 °C
Class B        :  Flammable liquids having flash point 23 °C and above but below 65 °C
Class C       :  Flammable liquids having flash point 65 °C and above but below 93 °C

Area classification as per NFPA is as follows:
Class-1 Zone 0 Areas: A Class I, Zone 0 location is a location that meets the following conditions:
Ignitable concentrations of flammable gases or vapors that are present continuously
Ignitable concentrations of flammable gases or vapors that are present for long periods of time.
Class I, Zone 1. Areas: A Class I, Zone 1 location is a location that meets the following conditions:
Ignitable concentrations of flammable gases or vapors that are likely to exist under normal operating conditions.
Ignitable concentrations of flammable gases or vapors that may exist frequently because of repair or maintenance operations or because of leakage.
Class I, Zone 2 Areas: A Class I, Zone 2 location is a location that meets the following conditions:
Ignitable concentrations of flammable gases or vapors that are not likely to occur in normal operation, and if they do occur, they will exist only for a short period.

The steps for HAC Study are as follows:
Methodology for Flammable Liquid and vapours:
Review Process Flow diagram
Prepare separate table for liquid and solid chemical along With flammable/combustible Properties
Classification of material as per NFPA-497
Selecting the Appropriate Classification Diagram
Determine the Zone classification
Determine Extent of the Classified Location
Review and recommendation
To enable selection of electrical equipment appropriate to the zone classification, the apparatus sub group and temperature class is then determined based on the flammable substances that can be release.
Methodology for Combustible dusts
Need For Classification
Facility information & history
Classification of material as per NFPA-499
Selecting the Appropriate Classification Diagram
Determine the Zone classification
Determine Extent of the Classified Location
Review and recommendation
To enable selection of electrical equipment appropriate to the zone classification, the apparatus sub group and temperature class is then determined based on the flammable substances that can be release.

The documents required for the HAC Study include the following:
Scope of work
Approved P&IDs
List of Chemicals
Process design basis
Hazardous inventories and their SDS
Process description
MSDS or Chemical properties of RM & FG
Equipment Design and Operating Condition /MOC
Equipments & Details
Layout & plot plan

The documents deliverables for HAC Study are as follows:
Executive Summary
Document Review
Submission of terms of reference
HAC Methodology
HAC Schedule
HAC Marked Layout
Comments Resolution sheets
Reference
List of tables
List of appendix

Following software will be used for HAC marking:
AutoCAD

Different guidelines used for HAC study are as follows:
IEC 60079-10-1 Explosive atmospheres Part 10-1: Classification of areas – Explosive gas atmospheres
IEC 60079-10-2 Explosive atmospheres Part 10-2: Classification of areas – Explosive dust atmospheres
Draft Version of EI15 Edition 4– Model Code of Safe Practice – Area Classification Code for Installations Handling Flammable Fluids. Energy Institute 2015. 3.
 EI15 Edition 3– Model Code of Safe Practice – Area Classification Code for Installations Handling Flammable Fluids. Energy Institute 2005.
IS 61241- “Electrical Apparatus for Use in the Presence of Combustible Dust – Code of Practice”
IS 5572- “Code of Practice for Electrical Installations of Industrial Establishments: Part 1 General Aspects”
 

Graphical representation of HAC Zones are as follows:

The meaning of Comment Resolution Sheet (CRS) is as follows:
A comment resolution sheet is a document used to track and address comments, feedback, or issues raised during a review process, audit, or evaluation.