The Most Frequently Asked Questions About Hazardous (Electrical) Area Classification

What is a hazardous (electrical) area classification?

It is a method to identify and categorize areas where flammable gases, vapors, or dust may be present, posing a risk of ignition and explosion. A Hazardous Area Classification (HAC) study is an essential analysis aimed at reducing the chances of igniting flammable materials. This study focuses on identifying sources of gases, vapors, and combustible dust, and implementing ignition control designs. HAC is a type of hazard and risk assessment specifically addressing the probability of explosive atmospheres (flammable dust/air mixtures) in certain areas. The classification is conducted following either the NFPA standard’s two Division system or the ATEX standard’s three Zone system.

What are the various groups in which materials are categorized for Hazardous Area Classifications?

Group designations are used to selectively divide a class into categories of material by relatively similar combustion characteristics. Groups are designed by the letters A through G. Groups A through D, are Groups for Class I, and E through G are Groups for Class II materials.

Group	Hazardous Material in Surrounding Atmosphere
Group A	Acetylene
Group B	Hydrogen, fuel and combustible process gases containing more than 30% hydrogen by volume or gases of equivalent hazard such as butadiene, ethylene oxide, propylene oxide, and acrolein.
Group C	Ethyl ether and ethylene or gases of equivalent hazard.
Group D	Gasoline, acetone, ammonia, benzene, butane, cyclopropane, ethanol, hexane, methanol, methane, natural gas, naphtha, propane or gases of equivalent hazard.
Group E	Metal conductive dusts, including aluminium, magnesium and their commercial alloys or other combustible dust whose particle size, abrasiveness and conductivity present similar hazards in connection with electrical equipment.
Group F	Carbonaceous dust, coal-black, charcoal, coal or coke dust that has more than 8% total entrapped volatiles or dust that has been sensitized by other material, so they present an explosion hazard.
Group G	Flour, sugar, starch, grain, wood, and plastic dust and chemicals

What is the comparison between North American Classifications and European & IEC Classifications?

A combustible liquid and gases zone hazardous (classified) location is subdivided into Zone 0, Zone 1, and Zone 2 while a combustible dust zone hazardous (classified) location is further subdivided into either Zone 20, Zone 21, or Zone 22, in which combustible dust is or might be present in the air or in layers, in quantities sufficient to produce explosive or ignitable mixtures.

North America		IEC (Europe)
Class –Division		Zones
Class I – Gas or vapor Class II – Dust Class III – Fiber or flying (No Group Designation)	Division 1:  Present or likely to be present during normal operation	Zone 0 (Gas) Zone 20 (Dust)	An explosive atmosphere is continually present or present for long periods of time.
		Zone 1 (Gas) / Zone 21 (Dust)	An explosive atmosphere is likely to occur in normal operation
	Division 2: Not present in normal operation, could be present in abnormal operation	Zone 2 (Gas)/ Zone 22 (Dust)	An explosive atmosphere is not likely to occur in normal operations and, if it does occur, will exist for only a short time.

What are the Regulatory Compliance and Standards for HAC

In the US, hazardous area classifications are governed by NFPA 70, National Electrical Code (NEC). The NEC provides requirements for electrical installations, including those in hazardous locations, in the United States.

• NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, provides guidelines for classifying hazardous locations where flammable gases and solvents are present.
• NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, provides guidelines for classifying hazardous locations where combustible dusts and fibers are present.

What are international standards that are used to define hazardous area classification or Zones?

The following international standards are used to define hazardous area classification zones, or their equivalent:

• EN 1127-1; Explosive atmosphere – Explosion prevention and protection. Part 1: Basic concepts and methodology
• EN 60079-10; Electrical apparatus for explosive gas atmospheres. Part 10: Classification of potentially explosive atmospheres

EN 50281-3; Electrical apparatus for use in the presence of combustible dust. Part 3: Classification of areas where dusts are or may be present

Why should we Perform Hazardous Area Classification?

Performing Hazardous Area Classification is an essential practice for ensuring safety in environments where explosive or flammable substances are handled. This classification involves analyzing areas of a facility to determine the presence and extent of hazardous conditions, typically categorized into zones based on the likelihood of an explosive atmosphere. By clearly identifying these areas, industries can implement appropriate safety measures, such as selecting suitable equipment and controls that are designed to operate safely in these conditions. This not only helps in preventing accidents like fires or explosions but also ensures compliance with safety regulations and standards. Hazardous Area Classification is fundamental for risk management, guiding the design, operation, and maintenance of facilities in a way that prioritizes the safety of personnel and the integrity of operations in the face of potentially hazardous environments.

What are some Potential Ignition Sources and Controls to be Considered in Hazardous Area Classification?

• Flames;
• Direct-fired space and process heating;
• Use of cigarettes/matches etc;
• Cutting and welding flames;
• Hot surfaces;
• Heated process vessels such as dryers and furnaces;
• Hot process vessels;
• Space heating equipment;
• Mechanical machinery;
• Electrical equipment and lights
• Spontaneous heating;
• Friction heating or sparks;
• Impact sparks;
• Sparks from electrical equipment;
• Stray currents from electrical equipment
• Electrostatic discharge sparks:
• Lightning strikes.
• Electromagnetic radiation of different wavelengths

In what way can ignition sources be effectively controlled in all hazardous areas?

• Using electrical equipment and instrumentation classified for the area in which it is located. New mechanical equipment will need to be selected in the same way.
• Grounding of all plant/ equipment.
• Elimination of surfaces above auto-ignition temperatures of flammable materials being handled/stored
• Provision of lightning protection
• Correct selection of vehicles/internal combustion engines that have to work in the zoned areas (see Technical Measures Document on Permit to Work Systems);
• Correct selection of equipment to avoid high intensity electromagnetic radiation sources, e.g. limitations on the power input to fiber optic systems, avoidance of high intensity lasers or sources of infrared radiation
• Prohibition of smoking/use of matches/lighters
• Controls over the use of normal vehicles
• Controls over activities that create intermittent hazardous areas, e.g. tanker loading/unloading
• Control of maintenance activities that may cause sparks/hot surfaces/naked flames through a Permit to Work System
• Precautions to control the risk from pyrophoric scale, usually associated with formation of ferrous sulphide inside process equipment

What are some best practices for hazardous area classification?

• Follow established engineering practices such as NFPA, API, NEC, IEC and PIP etc.
• Ensure that hazardous area requirements are established before purchasing equipment.
• Ensure that hazardous area classification layouts reflect the current status of the facility.
• Review and update layouts before each modification.
• Ensure that the addition of new equipment does not impact existing equipment / facility and if so, take corrective action.
• Ensure that the area classification “cloud does not encroach roads, walkways, occupied buildings, welding / fabrication yards etc.
• Perform a thorough review when introducing new sources of release in an existing facility.
• Ensure equipment installed in the classified area is rated for service conditions.
• Follow the manufacturer’s installation manual, applicable codes and standards.
• Maintain proper documentation.

What are some precautions to be taken in hazardous areas?

Precautions include compliance with classifications (according to NEC), training and awareness programs, prevention of ignition sources, regular maintenance and inspection, proper ventilation, use of appropriate Personal Protective Equipment (PPE), and implementation of an emergency response plan and permit-to-work system.

What main safety measures to take for Class I, Class II, and Class III locations?

Safety measures vary for each class. For Class I locations, use explosion-proof equipment and proper ventilation to handle flammable gases or vapors. Class II locations require dust-tight equipment and dust control to manage combustible dust hazards. In Class III locations, protect against ignitable fibers with proper enclosures and handling protocols.

What is explosion-proof Protection and intrinsically safe protection?

Explosion-proof protection is a type of protection that involves using an enclosure capable of withstanding an explosive gas or vapor within it. The enclosure also prevents the ignition of an explosive gas or vapor surrounding it. This type of protection operates at an external temperature that ensures the surrounding explosive atmosphere will not be ignited.

Intrinsically safe protection ensures that electrical equipment, under normal or abnormal conditions, is incapable of releasing sufficient electrical or thermal energy to cause ignition of a specific hazardous atmospheric mixture in its most easily ignitable concentration.

Why is hazardous area classification important?

It ensures the safe design, installation, and use of electrical equipment in areas where explosive atmospheres may occur, reducing the risk of ignition.

What are the main standards for hazardous area classification?

Key standards include the National Electrical Code (NEC) in the US, IEC 60079 in Europe, and ATEX directives.

What is the difference between Class, Division, and Zone classifications?

The Class/Division system (used in the US) categorizes areas into Classes and Divisions, while the Zone system (used internationally) uses Zones to define the presence and duration of hazardous atmospheres.

What is Class I in hazardous area classification?

Class I refers to areas where flammable gases or vapors may be present in sufficient quantities to produce explosive or ignitable mixtures.

What are the Divisions in Class I areas?

Division 1: Areas where ignitable concentrations of flammable gases or vapors exist under normal operating conditions.

Division 2: Areas where ignitable concentrations are not likely to exist under normal conditions but may occur under abnormal conditions.

What are Zones 0, 1, and 2 in hazardous area classification?

Zone 0: Areas where explosive gas atmospheres are present continuously or for long periods.

Zone 1: Areas where explosive gas atmospheres are likely to occur in normal operation.

Zone 2: Areas where explosive gas atmospheres are not likely to occur in normal operation but may occur for short periods.

What is Class II in hazardous area classification?

Class II refers to areas where combustible dusts may be present in sufficient quantities to produce explosive or ignitable mixtures.

What are the Divisions in Class II areas?

Division 1: Areas where ignitable concentrations of combustible dusts exist under normal operating conditions.

Division 2: Areas where ignitable concentrations of combustible dusts are not likely to exist under normal conditions but may occur under abnormal conditions.

What are Zones 20, 21, and 22 in hazardous area classification?

Zone 20: Areas where explosive dust atmospheres are present continuously or for long periods.

Zone 21: Areas where explosive dust atmospheres are likely to occur in normal operation.

Zone 22: Areas where explosive dust atmospheres are not likely to occur in normal operation but may occur for short periods.

What is Class III in hazardous area classification?

Class III refers to areas where easily ignitable fibers or flyings are present but not likely to be in suspension in the air in quantities sufficient to produce ignitable mixtures.

What are the typical sources of ignition in hazardous areas?

Sources include electrical sparks, hot surfaces, static electricity, open flames, and friction.

How do you determine the classification of a hazardous area?

By assessing the types of materials present, their properties, potential sources of release, and the likelihood and duration of their presence.

What is an intrinsically safe device?

It is a device designed to operate in hazardous areas by limiting energy, both electrical and thermal, to levels below those required to ignite a specific hazardous atmospheric mixture.

What is explosion-proof equipment?

Equipment designed to contain any explosion within its housing and prevent the ignition of the surrounding hazardous atmosphere.

What is the purpose of purging in hazardous areas?

Purging is used to replace the hazardous atmosphere within an enclosure with a safe gas, reducing the risk of ignition.

What is the difference between Type Z, Y, and X purging?

• Type X: Reduces the classification inside the enclosure from Division 1 or Zone 1 to non-hazardous.
• Type Y: Reduces the classification inside the enclosure from Division 1 or Zone 1 to Division 2 or Zone 2.
• Type Z: Reduces the classification inside the enclosure from Division 2 or Zone 2 to non-hazardous.

What is a hazardous area classification drawing?

It is a detailed plan that outlines the classified areas within a facility, specifying the extent and type of hazardous zones or divisions.

What role does ventilation play in hazardous areas?

Proper ventilation reduces the concentration of hazardous gases, vapors, or dusts, thereby reducing the risk of ignition.

How often should hazardous area classifications be reviewed?

They should be reviewed periodically and whenever there are significant changes in processes, materials, or equipment.

What is a gas group in hazardous area classification?

Gas groups classify gases and vapors based on their ignitability and explosive properties. Common groups are Group IIA, IIB, and IIC.

What is the temperature classification in hazardous areas?

It is a classification that indicates the maximum surface temperature of equipment, ensuring it is below the ignition temperature of the hazardous atmosphere.

How do you select appropriate electrical equipment for hazardous areas?

By ensuring the equipment meets the specific requirements of the area’s classification, including gas group and temperature class.

What is the role of a hazardous area consultant?

A consultant helps identify, classify, and mitigate hazards in potentially explosive atmospheres, ensuring compliance with relevant standards and regulations.

Can non-electrical equipment cause explosions in hazardous areas?

Yes, non-electrical sources like hot surfaces, mechanical sparks, and friction can also ignite explosive atmospheres.

What is the ATEX directive?

ATEX is a European Union directive that specifies equipment and protective systems intended for use in potentially explosive atmospheres.

What are the two ATEX categories?

• Category 1: Equipment for areas where explosive atmospheres are present continuously, frequently, or for long periods.
• Category 2: Equipment for areas where explosive atmospheres are likely to occur in normal operation.

What is the IECEx certification?

IECEx is an international certification system that ensures equipment and services comply with IEC standards for use in explosive atmospheres.

What are intrinsic safety barriers?

These are devices used to limit the electrical energy that can reach hazardous areas, ensuring it remains below ignition levels.

What is the importance of maintenance in hazardous areas?

Regular maintenance ensures that all safety systems and protective measures remain effective, preventing the risk of ignition due to equipment failure or degradation.

What services does Prime Process Safety Center offer?

Prime Process Safety Center offers the following Combustible Dust Consulting Services; Combustible Dust Hazard Analysis (DHA), Ignition Sources Assessment, Electrostatic Hazard Assessment, Hazardous Area Classification, Fire and Explosion Hazard Analysis, Explosion Prevention and Protection Consulting Services, Fire and Building Code Services, Incident Investigation, Expert Witness and Litigation. Moreover, Prime Process Safety Center offers the following combustible dust testing services Go/No Go Explosibility Screening, Burn Rate / Fire Train Test, Dust Explosion Severity (Kst/Pmax/dP/dt), Minimum Explosible Concentration (MEC)/Lower Explosible Limit (LEL), Limiting Oxygen Concentration (LOC) Test, Minimum Ignition Energy (MIE), Minimum Autoignition Temperature-Cloud (MAIT – Cloud), Layer Ignition Temperature of Dust (LIT), Volume Resistivity, Surface Resistivity, Charge Decay (Relaxation) Time, Breakdown Voltage, Flexible Intermediate Bulk Containers (FIBC), Electrostatic Chargeability Testing, Basket Self-Heating, Grewer Oven Test, Air Over Layer/Powder Layer Test, Bulk Powder Test, Aerated Powder Test