Hazardous Area Classification

It’s the process of analyzing and classifying areas in industrial settings where flammable gases, vapors, mists, or dusts could create an explosive or fire hazard.

It’s crucial for ensuring the safe selection and installation of equipment, reducing the risk of ignition in areas with potentially explosive atmospheres, and ensuring compliance with safety regulations.

Industries like oil and gas, chemical manufacturing, pharmaceuticals, food processing, and any others where flammable materials are processed or stored.

Areas are classified based on the type, concentration, and likelihood of the presence of hazardous substances, typically into Zones (for gases and vapors) or Divisions (for dusts).

The most common standards include the National Electrical Code (NEC) in the US, the International Electrotechnical Commission (IEC) standards, and the European ATEX directives.

The Zone system, used internationally, categorizes areas into Zones 0, 1, and 2 for gases and 20, 21, and 22 for dusts, while the Division system, used mainly in North America, classifies areas into Division 1 and 2.

Qualified professionals with expertise in process safety and knowledge of applicable standards should conduct these classifications.

Factors include the type of hazardous materials present, their physical and chemical properties, operational processes, environmental conditions, and facility layout.

It determines the type of explosion-proof or intrinsically safe equipment that should be used in different areas to prevent ignition of hazardous atmospheres.

No, it should be reviewed and updated regularly, especially when there are changes in processes, materials, or facility layout, to ensure ongoing safety compliance.

• 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

• 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 fibre 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

• 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.

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.

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.

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.