Understanding Hazardous Area Classifications and the DSEAR Assessment Process
Managing dangerous substances in the workplace requires a comprehensive understanding of hazardous area classifications and the DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) assessment process. Proper management of dangerous substances is crucial to mitigate risks such as fire, explosion, and corrosion of metal.
In this article, we will delve deeper into the key aspects of managing dangerous substances in your workplace, focusing on the Determination of Hazardous Area Classifications and the DSEAR Assessment and Determination Process.
Discover how to effectively manage dangerous substances in your workplace with a FREE initial consultation.
Identifying Dangerous Substances
Dangerous substances can come in various forms, including flammable liquids, solvents, powders, and dusts. Identifying these substances is essential as they pose significant risks.
If your workplace involves the storage, use, or generation of vapours or dust environments, you likely fall under the scope of the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) [^1].
Understanding Chemical Characteristics
To conduct a competent DSEAR assessment, it’s crucial to have a solid understanding of key chemical terms. Some important characteristics include: 
- Vapour density: The density of a chemical’s vapour compared to the density of air.
- Flash point: The lowest temperature at which a substance emits enough vapour to ignite.
- Boiling point: The temperature at which a substance changes from a liquid to a gas.
- Vapour pressure: The pressure exerted by a substance’s vapour in equilibrium with its solid or liquid form.
- Dispersion rate: The speed at which a vapour or dust cloud spreads throughout an area.
In addition to these characteristics, other factors such as the containment of substances in storage tanks, the quantity and frequency of use, and how substances are used must be considered in a suitable and sufficient assessment.
Determination of Hazardous Area Classifications:
The primary objective of a DSEAR assessment is to identify the risk of fire or explosion and implement necessary precautions. Hazardous areas are categorised based on the presence of gases, vapours, mists, or combustible dusts.
These areas are defined by standards such as BS-EN 60079, which provide detailed information on equipment selection, protection, inspection, and maintenance of electrical installations [^1].
Hazardous Area Classification Categories
To determine the hazardous area classification, various factors such as the nature and quantity of the dangerous substances, ventilation, and the likelihood of their release are considered. The classification is as follows:
Gases, Vapours, and Mists:
- Zone 0: An area where an explosive atmosphere of dangerous substances in the form of gas, vapour, or mist is continuously present or present for long periods.
- Zone 1: An area where an explosive atmosphere of dangerous substances in the form of gas, vapour, or mist is likely to occur under normal operating conditions.
- Zone 2: An area where an explosive atmosphere of dangerous substances in the form of gas, vapour, or mist is not likely to occur under normal operating conditions, or if it does, it will only be for a short duration [^1].
- Zone 20: An area where an explosive atmosphere in the form of a cloud of combustible dust in air is continuously present or present for long periods.
- Zone 21: An area where an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur under normal operating conditions.
- Zone 22: An area where an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur under normal operating conditions, or if it does, it will only be for a short duration [^1]
You can read more about these zones on the British Standard Institution (BSI) website [^1].
DSEAR Assessment Process:
The DSEAR assessment process involves a systematic evaluation of fire and explosion risks associated with dangerous substances. The process can be broken down into the following key stages:
- Stage 1 – Assessment Survey: Identify potentially flammable or explosive substances present in the workplace, considering their type, quantity, and characteristics.
- Stage 2 -Formation of Flammable Atmospheres: Determine the factors that could lead to the formation of potentially flammable atmospheres under normal and abnormal conditions, including material properties, process conditions, and potential ignition sources.
- Stage 3 – Control and Mitigation Measures: Identify and evaluate existing control and mitigation measures in place, such as ventilation systems, isolation procedures, and personal protective equipment.
- Stage 4 – Effectiveness of Mitigation Measures: Assess the effectiveness and maintenance of the identified control and mitigation measures, ensuring they are suitable and sufficient for managing the identified risks.
- Stage 5 – Dispersion Characteristics: Evaluate the dispersion characteristics of potentially flammable atmospheres, considering factors like ventilation, confinement, and the release rate of dangerous substances.
- Stage 6 – Special Precautions: Determine the necessity of any additional special precautions, such as explosion relief venting, inerting, or the use of explosion-resistant equipment.
- Stage 7 – Hazardous Area Classification: Establish the hazardous area zone types based on the identified risks and create a hazardous area classification drawing, indicating the extent of each zone.
- Stage 8 – Electrical Equipment Protection: Define the level of protection required for electrical equipment installed in hazardous areas, considering factors like motors, junction boxes, lighting, and wiring systems.
You can find more detailed guidance on the DSEAR assessment process on the Health and Safety Executive (HSE) website 
By following a systematic approach to DSEAR assessments, businesses can effectively manage the risks associated with dangerous substances, promoting a safe working environment for employees.
Understanding hazardous area classifications and conducting thorough DSEAR assessments are essential for managing dangerous substances in the workplace. For expert guidance in navigating these complexities, Compass HSC Ltd, a trusted consultancy with extensive experience in conducting DSEAR risk assessments, can provide practical and reliable advice. Safeguard your workplace by choosing Compass HSC Ltd as your reliable partner in managing health and safety risks [^5].
Not quite sure where to start? Contact the team for a free consultation!
Compass HSC – DSEAR Consulting