What is Hazardous Area Classification?
Hazardous Area Classification (HAC) is a systematic process used to segregate a facility into hazardous and non-hazardous areas. The hazardous areas are further subdivided into zones based on the probability and duration of the presence of a flammable atmosphere during normal operation.
This classification is crucial for safety and compliance with IEC and ATEX standards. The process begins by identifying potential sources of flammable substance release, from which a three-dimensional space is established, forming a ‘Zone’.
Flammable atmospheres can come in the form of either Gases, Vapours, Mists or Combustible Dusts, and in some instances a combination of these.
Special precautions then need to be implemented so as not to introduce ignition sources into the zones in the form of Electrical and Non-Electrical equipment, along with personnel operating in and around the zones.
Hazardous Area Classification prescribes Zone extents by utilising guidance and standards such as IEC 60079, NEC 500, EI part 15 or API RP 500/505. By successfully establishing Zone extents and the properties of flammable atmospheres, it is only then possible to assess whether electrical, mechanical, or other equipment requires specific protective measures to prevent fire or explosion risks.
In the UK, the requirement for a Hazardous Area Classification to be undertaken is systematic approach mandated by the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR), which came into force on 9th December 2002.
Effective communication in the HAC process is ensured through the production of and availability of appropriate documentation, including HAC drawings or HAC tables to personnel who operate in and around potentially flammable atmospheres.
Why is Hazardous Area Classification Important?
Hazardous Area Classification involves analysing and classifying environments based on the type of flammable material present and the likelihood of its presence. Typically, these classifications are developed by a team of Process and Electrical engineers, with input from specialists in plant operations and Health, Safety, and Environment (HSE) professionals. This collaborative effort ensures informed decisions to maintain safety and operational integrity.
Without knowledge of the location and property of a flammable atmosphere, it is easily possible to introduce a potentially fatal ignition source.
Assuming that a flammable atmosphere is present, when indeed it is not, despite a ‘safer’ means of operation, is very costly. Therefore, it is essential for Hazardous Area Classification (HAC) to be carried out correctly, and be reviewed on a regular basis, including whenever changes to plant or process occur.
Where equipment needs to be located within the presence of a potential flammable atmosphere, or ‘Zone’, this it needs to be manufactured and certified to an approved by a notified body, ensuring that it has the correct protection type afforded to be proven safe for these areas, such as Explosion-Proof (Ex d), Increased Safety (Ex e), Intrinsic Safety (Ex i), or Dust Proof (Ex tD).
Undertaking a Hazardous Area Classification
Determining the Grade of Release
Once sources of release have been identified, the next key step is to determine the grade of release, which categorises the nature and persistence of a flammable atmosphere, eventually defining hazardous zones as follows:
- Continuous Release: This indicates the presence of a flammable atmosphere continuously or for long periods. This usually happens if the flammable liquids are above their flashpoint and involves an opening in the containment system.
- Normal Operation: In some cases, ignition may only occur during specific operations such as tank filling when a vent releases vapours and a flammable atmosphere is produced.
- Infrequent Release: Low-level spillages or leaks are associated with such infrequent occurrences; they typically do not result in the presence of a flammable atmosphere.
Key Steps of the HAC Process:
- Information Gathering: Classify the materials (flammable gases, vapours, liquids, or dusts) used or produced in the area and their physical-chemical properties such as flash points, autoignition temperatures, and explosive limits.
- Process Review: Review all processes and operations, including how materials are handled, stored, and processed. Identify sources of release such as valves, flanges, pumps, and storage tanks.
- Environmental Analysis: Evaluate the environmental conditions in terms of ventilation (natural or mechanical) and temperature or pressure levels which may alter the behaviour of hazardous materials.
- Zone Determination: Define the extent of hazardous zones by applying relevant standards and guidelines, best engineering practices, and specialist engineering judgement.
- Documentation & Record Justification: Provide detailed documentation (i.e., drawings, tags, and legends) for identification and classification purposes. Maintain records itemising the factors and assumptions used during classification.
- Equipment Selection: Choose appropriate equipment that meets the determined safety requirements.
- Safety Measures: Implement and maintain appropriate safety measures, such as regular maintenance, training, and awareness programs, to ensure ongoing safety.
Following these steps ensures a complete and systematic approach to managing hazardous areas, thereby aiding safe operation and preventing risks associated with flammable atmospheres.
Ignition Risks
The original purpose of Hazardous Area Classification (HAC) has expanded in recent years. Initially, the system helped companies choose electrical equipment to prevent ignition in flammable atmospheres. HAC has since developed into an essential tool for evaluating and reducing the risk of various ignition sources, such as electrostatic discharge and mechanical impacts.
Zones are identified as hazardous areas where precautions to avoid ignition sources must be implemented.
According to BS EN 1127-1:2019, we should apply precautions using two main methods:
- Frequency of the Ignition Source Presence: This principle discusses how frequently an ignition source may be present.
- Likelihood of the Ignition Source Being Effective: This depends on two factors:
- The strength of the specific ignition source, measured by temperature or the amount of energy dissipated.
- The ignition sensitivity of the flammable materials.
These guidelines allow industries to take appropriate and effective steps regarding the prevention of ignition and maintaining safety in hazardous areas.
Zone 0, 1, and 2 Hazardous Areas
A hazardous area is any place with explosion risk. Each hazardous area is unique and has specific requirements based on the nature of the atmosphere and the elements present. For an explosion to occur, there must be flammable or explosive gases, vapours, mists, or combustible dust or combination. The risk level of an explosion depends on how often and for how long these explosive atmospheres are present.
We categorise this risk into different zones:
| Zone 0 (20) | Flammable atmosphere present continuously |
| Zone 1 (21) | Flammable atmosphere is likely to be present |
| Zone 2 (22) | Flammable atmosphere is not likely to be present |
- Zone 0: This is an area where an explosive atmosphere is present all the time, for long periods, or frequently.
- Zone 1: In this area, an explosive atmosphere might occur occasionally during normal operations, like during repairs, maintenance, or due to leaks.
- Zone 2: Here, an explosive atmosphere is unlikely during normal operations, but if it does happen, it will only last for a short period. Often in the case of a foreseeable accident.
For dust atmospheres, the classifications are slightly different:
- Zone 20: An area 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
- Zone 21: An area where a hazardous dust atmosphere in the form of a cloud of combustible dust in air, is likely to occur, occasionally, during normal operations.
- Zone 22: An area where a hazardous dust atmosphere in the form of a cloud of combustible dust in air, is not likely to occur during normal operations, but if it does happen, it will only last for a short period.
By understanding and categorising these zones, we can implement the necessary safety measures to mitigate the risks of explosions in different environments.
F.E.S. (EX) Approach to Hazardous Area Classification
Hazardous Area Classification has widespread applications across all industries that produce or operate with flammable materials, from chemicals to food processing to power generation.
At F.E.S. (EX), we service all sectors across the UK, Europe and beyond, following a thorough, systematic and pragmatic approach to undertaking Hazardous Area Classification (HAC). First, we assemble a team of hazardous area specialists who understand your facility’s operations, electrical equipment, and processes inside-out.
We start by collecting crucial flammability information about the materials involved, conducting tests, if required, to assess explosion and ignition risks on various substances. Using this information, we then identify potential sources of release and evaluate the presence of ignitable mixtures, ensuring that no hazards are missed.
Our top priority is your safety, so we look to provide clear, precise and concise documentation, which thoroughly prescribing, Zone extents and their properties, along with the appropriate equipment ratings to meet the latest standards and legislative requirements, thus, creating a comprehensive live document for your facility.
Choosing F.E.S. (EX) gives you access to our regulatory and industrial expertise. We navigate the complexities of HAC on your behalf, ensuring that all safety and compliance requirements are met. With a global perspective and disciplined methodology, we are the perfect partner for your HAC needs worldwide. Start your pre-assessment today and discover the full benefits of our service. Safety and compliance come first at F.E.S. (EX).
Hazardous Area Classification
Case Study
F.E.S. (EX) Limited carried out a Hazardous Area Classification for a client with a storage tank bund containing multiple tanks and pumps. The client requested our team to classify the zoning for hazardous area classification of the bund and identify any equipment that required inspection or replacement.
They initially designated the bund as Zone 2 throughout, with a Zone 1 classification in the sump. This designation followed standard classification procedures. However, the question “Why is there a Zone 2 in the first place?” had not been previously addressed. Most tanks in the bund contained non-flammable liquids like acids, except for one tank holding a flammable liquid in a corner of the bund. The initial categorisation correctly identified that this tank could leak, spreading the flammable liquid throughout the bund and requiring all equipment to be suitable for Zone 2. This led to appropriate inspections and maintenance schedules.
Rather than treating hazardous area classification as a final step, we treated it as the starting point of our risk assessment. To minimise ongoing costs, we recommended enclosing the solvent tank in its own bund with two extra walls, effectively isolating it in its own corner. This modification allowed us to remove all other tanks and pumps in the bund from the hazardous zone, reducing ongoing costs related to hazardous area classification. Hazardous area classification should not just be a formality but an integral part of process safety design and cost minimisation.
Why Choose F.E.S. (EX) for Hazardous Area Classification?
Opting for Hazardous Area Classification from F.E.S. (EX) Limited ensures you receive the best advice and expertise to achieve full compliance every time. With our deep understanding of industrial processes and facilities, we have the proficiency needed to navigate the complex classification process and ensure adherence to both current and future regulations.
At F.E.S. (EX), we go beyond local standards and regulations by applying global best practices across various sectors, including aerospace, oil and gas, power systems, and chemicals. Our team’s extensive experience in these industries allows us to provide optimal solutions tailored to your specific needs.
Hazardous area classification measures the likelihood of an explosive atmosphere forming but does not account for the properties of the materials being handled. This highlights the importance of partnering with a professional organisation like F.E.S. (EX) Limited. We offer a comprehensive range of services, including process safety, electrical safety, installation and commissioning, as well as maintenance and inspection.
Our international focus and disciplined methodology make us the most qualified provider of global HAC support. Trust F.E.S. (EX) Limited to deliver full-service licence management and compliance solutions, ensuring your operations are safe, productive, and compliant.