how do you classify hazardous areas

After the sources of release are identified, they can be classified into three grades, with corresponding hazardous area zones:

• Continuous – a flammable atmosphere will be present continuously or for long periods. Commonly resulting in a Zone 0 or Zone 20, for gases and/or vapours or dust atmospheres respectively
• Primary – a flammable atmosphere is likely to be present occasionally and for a short duration during normal operation. ...
• Secondary – present in abnormal or failure condition. ...

Full Answer

What is the zone system of hazardous area classification?

Hazardous area Zone Classification. The Zone system of hazardous area classification, defines the probability of the hazardous material, gas or dust, being present in sufficient quantities that can generate explosive or ignitable mixtures. Refer to Fig.3 that shows the hazardous area zone classification based on hazardous gas release grade.

How are hazardous areas classified in North America?

In North America, instead, hazardous areas are classified by the Class/Division system - or by a Zone system adapted to the IEC standards. A Zone defines the frequency and duration of the occurrence of an explosive atmosphere. The Zone system has 3 levels of hazard for gas or dust.

What is an area classification?

Area classification is the division of a plant or installation into hazardous areas and non-hazardous areas. The hazardous areas are further subdivided into zones.

What are the three components of a hazardous area?

Hazardous Area Classification. An industrial area is considered a hazardous area when it contains three fundamental components: A flammable substance (which can be a gas, liquid, or solid), an oxidizer, and a source of ignition.

How do you do the area classification?

1:2146:59How to do a Hazardous Area Classification (HAC) periodical ...YouTubeStart of suggested clipEnd of suggested clipPart of the control step is to classify. Places where explosive atmospheres may occur. In two zonesMorePart of the control step is to classify. Places where explosive atmospheres may occur. In two zones and mark those zones where necessary.

WHO classifies a hazardous location?

the National Fire Protection AssociationIn the United States, the hazardous location classification system is defined by the National Fire Protection Association (NFPA) 70®, National Electric Code® (NEC).

What are the three classes of hazardous locations?

Class I locations are those in which flammable vapors and gases may be present. Class II locations are those in which combustible dust may be found. Class III locations are those which are hazardous because of the presence of easily ignitable fibers or flyings.

What is the purpose of hazardous area classification?

Hazardous area classification is: a method of analysing and classifying an area to facilitate appropriate equipment selection. key to reducing the risk of fires or explosions and keeping dangerous work environments safe. critical in protecting people, plant and equipment.

What is the difference between Class 1 Division 1 and Division 2?

Class 1 Hazardous Locations refer to facilities that deal with flammable gases, vapors, and liquids. Division 2 specifies that flammable materials are handled, processed, or used at a location. But, concentrations of hazardous substances are not high enough to be ignitable.

Why is it important to identify the different types of hazardous locations?

Hazardous area classification is the evaluation and classification of hazardous locations using scientific and engineering principles in companies where chemicals are manufactured or utilized. These areas are classified to ensure the safe and proper specification and installation of electrical equipment.

What is a Class 2 hazardous location?

Class II Locations The second type of hazardous location is called a “Class II Location”. This classification is created by the presence of combustible dust in the air in sufficient quantities to be explosive or ignitable.

What is a Class 1 Division 1 area?

A Class I, Division 1 area encompasses the combination of Zone 0 and Zone 1 areas. An area where ignitable concentrations of flammable gases, vapors or liquids are present continuously or for long periods of time under normal operating conditions.

What does Class 1 Group D mean?

Class I Group D locations are atmospheres containing elements such as Gasoline, Hexane, Naphtha, Benzine, Butane, Propane, Alcohol, Acetone, Benzol, Lacquer Solvent Vapors or Natural Gas.

What defines a hazardous area?

A hazardous area is a three-dimensional space in which an explosive atmosphere is or may be expected to be present or form. Electrical equipment within the hazardous area must be suitably rated and effectively earthed to ensure that any ignition risks are adequately controlled.

What is hazardous area classification schedule?

Hazardous area classification drawing outlines the classifications of areas where flammable liquids, gasses or vapors are handed, processed or stored. It is created based on input from the Process Flow Diagrams, Piping & Instrumentation Diagrams and the Equipment Location Plan.

What is the 5 types of hazard?

HazardsChemicals.Ergonomic.Health.Physical.Psychosocial.Safety.Workplace.

What is hazard location explain hazardous location classes?

ClassesClassDefinitionIA location in which a flammable gas or vapour is or may be present in sufficient quantity to cause an explosive atmosphereIIA location in which a conductive or combustible dust is or may be present in sufficient quantity to cause a fi re or an explosive hazard1 more row

What is the most hazardous classification on a job site?

Group AGroup A is considered the most hazardous, with Group D being the least hazardous for gases and vapors. The explosive characteristics of the air mixtures of gases, vapors, or dusts vary with the specific material involved.

What is a Class 1 Division 2 location OSHA?

Note to the definition of "Class I, Division 2:" This classification usually includes locations where volatile flammable liquids or flammable gases or vapors are used, but which would become hazardous only in case of an accident or of some unusual operating condition.

What is a Division 2 hazardous area?

Division 2 is also a subset of Class I and is classified as an area where the explosive or flammable gases, vapors or liquids mentioned above are not likely to exist during regular operation.

What are the three sub-groups of gas?

Each gas falls into one of three gas sub-groups IIA, IIB & IIC, the sub-group that a gas falls into is determined by how volatile/destructive they would be if ignited, where gases in sub-group IIC are more volatile/destructive than those in IIA. (See Table 2).

What are the two criteria to be considered when classifying a potentially hazardous vapour environment?

Two main criteria to be considered when classifying a potentially hazardous vapour environment are: The area where the probability of the hazardous vapour or gas being present, referred to as “zones”. An understanding of the particular type of vapours & gases present; these are then categorised into “gas groups”. 1.1. Zones.

Do some areas have ignitable vapours?

Some areas will have these vapours present for long periods or even at all times, others areas will only experience the presence of ignitable vapours at certain times. Due to the varying levels of vapours present on these facilities they are categorised into sections known as zones.

How are hazardous areas classified?

In North America, instead, hazardous areas are classified by the Class/Division system - or by a Zone system adapted to the IEC standards.

What is a hazardous area?

Consequently a “Hazardous Area” (gas) is an area in which there is (or it’s expected to be present) an explosive gas atmosphere in quantities such as to require special precautions for the construction, installation and use of equipment.

What is zone system?

Zones. A Zone defines the frequency and duration of the occurrence of an explosive atmosphere. The Zone system has 3 levels of hazard for gas or dust. Gases, Vapors and Mists (IEC 60079-10-1 Classification of areas - Explosive gas atmospheres):

What is an explosive atmosphere?

According to the standard, an “Explosive Atmosphere” is a mixture with air, under certain atmospheric conditions, of flammable substances in the form of gas, vapor, dust, fibers, or volatiles which , after ignition, permits self-sustaining propagation.

What is an ATEX certification?

Outside of North America, ATEX (Appareils destinés à être utilisés en ATmosphères EXplosives) and IEC (International Electrotechnical Commission) provide standards that are recognized internationally. These organizations, unlike FM, UL and CSA, do not perform their own testing but rather have notified bodies perform the testing to meet the standards they set. Many North American companies will certify their products to ATEX and/or IEC standards in order to make them applicable to international businesses. Though there are differences between the certifications that these organizations offer, the major reasons for choosing a product certified through one organization over another are the location of the facility and the requirements of the local regulations.

What is a division in hazardous areas?

Furthermore, a division or zone is assigned to the product. This is a description of the frequency with which the combustible gas and/or dust is present within the hazardous area . Divisions were used in older North American hazardous area standards, while zones are used in European/International standards as well as newer North American Standards.

How to prevent explosions in hazardous areas?

First, an explosion-proof, flame-proof, or powder-filled device is one in which the explosion is contained and extinguished. Second, limiting the energy of the device to a point where combustion becomes impossible even in the presence of a flammable material, effectively removing the ignition source, is known as intrinsically safe or nonincendive. A non-incendive device prevents ignition under normal conditions. An intrinsically safe device prevents ignition in doublefault conditions. Lastly, a device can simply keep the flammable materials out of the electrical or heat producing components through pressurization, encapsulation, oil emersion, fiber and flying protection, or protection by enclosure. The particular protection concept that a device uses is represented by a marking on the device such as AEXd (Flameproof C1 Z1), Ex ia (I.S. CI Z0). These markings can be looked up on tables and charts available online from the various hazardous area approval agencies.

What is considered a hazardous area?

Hazardous Area Classification. An industrial area is considered a hazardous area when it contains three fundamental components: A flammable substance (which can be a gas, liquid, or solid), an oxidizer, and a source of ignition. The flammable substance can be anything from gasses and liquids such as hydrogen, gasoline and kerosene, ...

What is equipment group?

The equipment group describes the type of hazardous material that is or could be present in the hazardous area. North American and international organizations use different standards to represent the equipment group, but they all describe the same thing: the type of combustible material in the presence of which the equipment can be operated.

What is the temperature rating of a device?

Lastly, a device meant for use in a hazardous area is assigned a temperature class. The temperature class is the maximum ambient surface temperature the device can reach (under maximum dust layers where applicable). This rating is given to help prevent combustion based on the combustion point of the material present in the area. This is used to determine the ambient operating temperature of the device. The approved product will also have a maximum ambient operating temperature. Most facilities will want to operate at a maximum of 80% or below of the maximum ambient operating temperature. Some examples of temperature ratings commonly seen on devices are T1 (450°C), T3 (200°C), T4 (135°C), and T6 (85°C). Traditional US and Canadian systems may also include such temperature classes as T2A, T2B, T3C, etc., which indicate more precise temperature ratings.

What is hazardous area equipment?

Hazardous area standards require the use of equipment specifically certified for use in areas that have all three of the above ingredients for an explosion. Though the goal of all hazardous area equipment is to prevent an explosion, the methods that they use vary depending on their manufacture and intended application.

What is zone NFPA 70?

The Zones are based on how often the hazard is present rather than upon normal versus abnormal conditions. NFPA 70 NEC Hazardous Locations Zones.

What is class in flammable gases?

Class defines the type of explosive or ignitable substances which are present in the atmosphere. Division defines the likelihood of the hazardous material being present in an explosive or ignitable concentration. C lass I flammable gases and vapors are grouped into one of four groups (Groups A, B, C or D) based on their physical properties and the ease in which they can be ignited. Class II combustible dusts are grouped into one of three (3) groups: E combustible metal dusts, F combustible carbonaceous dusts or G other combustible dusts.

What is the OSHA code for hazardous equipment?

In 29 CFR 1910.307 (c) (2) (ii), OSHA requires all equipment used in a hazardous location to be marked with the class, group and operating temperature or temperature range for which it is approved.

What is NFPA 70 NEC?

NFPA 70 NEC uses the familiar Class/Division system and has added an Americanized version of the International Electrochemical Commission’s (IEC) IEC Zone system which maintains the NEC wiring methods and protection techniques. NFPA 70 NEC Articles 500 through 503 cover the requirements for electrical/electronic equipment ...

What is zone classification?

The Zone Classification System is offered as an alternative to the Class and Division system. It is an Americanized version of the International Electrochemical Commission’s (IEC) Zone system which maintains the NEC wiring methods and protection techniques. Zone defines the general nature – if it is a gas or dust – and the probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere. The Zones are based on how often the hazard is present rather than upon normal versus abnormal conditions.

What is a hazardous classified location?

Hazardous classified locations are areas where the possibility of fire or explosion hazards may exist under normal or abnormal conditions because of the presence of flammable, combustible or ignitable gases, vapors, liquids, dust, or fibers/flyings. These areas are classified solely for the purpose of ensuring the safe and proper specification and installation of electrical/electronic equipment.

What is a group in hazardous materials?

Group defines the type of hazardous material and partly the location of the surrounding atmosphere .

What is a Class I hazardous location?

Class I locations are those in which flammable gases, flammable liquid–produced vapors, or combustible liquid–produced vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.

Why are hazardous locations important?

Hazardous locations exist in a variety of occupancies because of the materials handled, processed or stored in them. The materials are a fire or explosion hazard. Through industry experience, techniques have been and continue to be developed that enable these hazardous materials to be used safely. A variety of occupancy and process standards, address many of the safety precautions. The charge of the NEC is to provide the necessary safeguards to ensure the electrical installation will not be an ignition source.

What is the NEC classification system?

The NEC uses two systems to classify hazardous locations. The traditional system, which has been used in the United States and Canada for many years, is based on classes, divisions and groups. The NEC also provided an area classification system that is based on zones. The zone system is based on standards of the International Electrotechnical Commission (IEC). The first part of the IEC classification scheme originally appeared in the 1996 edition of the NEC. It allowed the use of additional types of equipment in large industrial and petrochemical facilities, and equipment protection techniques the NEC hadn’t previously recognized.

What is division 1?

A simplification of the definition for a Division 1 location is a location in which the hazard can be expected to exist in normal operations, or it can exist as a result of equipment breakdown that may cause the hazard to exist along with a simultaneous ignition hazard. For Class I and II locations, a simplified explanation is that, in Division 1 locations, the hazard can exist under normal operating conditions. This does not necessarily mean it exists continuously. For most installations, it will not exist continuously, because ignition sources, other than those controlled by the NEC’s rules, also exist within most industrial and manufacturing processes.

Why are Class II buildings hazardous?

Class II locations are hazardous because of the presence of combustible dust.

Why are Class I and Class II locations more common?

Class I locations are more common than Class II locations because those types of materials are in far wider usage.

Is sawdust a combustible material?

Sawdust is not dust because the particles are too big. Sawdust is a combustible fly ing (Class III) material. Class III hazards are not explosion hazards. They are fast-burning fire hazards. Housekeeping is critical in Class II and Class III locations. Vacuum cleaners are often used to keep dust accumulations under control; however, NFPA 499 states the vacuum cleaner must be an approved type, so it does not become an ignition source.

How many groups of gases are there?

All gases and vapours can be classified into 4 major gas groups. The classification criteria is based upon laboratory tests to determine the maximum experimental safe gap (MESG) and the minimum ignition current (MIC). Gas group classification for typical gases will be:

Is electrical equipment rated for surface temperature?

Any electrical equipment to used in an hazardous area is also tested and rated for its maximum surface temperature. It now becomes relatively simple to ensure that the temperature rating of the equipment is always compatible with temperature classification of the gas.