Hazardous Area Classification Under DSEAR

Hazardous Area Classification Under DSEAR: What Surrey Businesses Need to Know

Of all the elements that make up a complete DSEAR assessment, hazardous area classification is arguably the one that businesses find most technically challenging — and most easy to overlook.

Yet under Regulation 7 of DSEAR, it is a legal requirement where dangerous substances are present, and it forms the foundation for a range of downstream decisions about equipment selection, signage, and safe working practices.

Here’s a practical overview of what hazardous area classification involves, why it matters, and what you need to have in place.

What is Hazardous Area Classification?

Hazardous area classification is the process of identifying and mapping locations within a workplace where explosive or flammable atmospheres could form.

The purpose is to determine where controls over potential ignition sources are needed — and, equally importantly, where no such risk exists.

It must be carried out by a competent person before work involving dangerous substances commences.

The classification is based on the frequency and duration of the occurrence of an explosive atmosphere, and places are divided into three zone types.

Zone 0 is a place where an explosive atmosphere is present continuously, for long periods, or frequently.

Zone 1 is a place where an explosive atmosphere is likely to occur occasionally during normal operation.

Zone 2 is a place where an explosive atmosphere is not likely in normal operation, but if it does occur, it will persist for only a short period.

In some cases, a zone of negligible extent, designated NE, may arise.

This can be treated as non-hazardous, meaning that if an explosion were to occur it would have negligible consequences.

This is a particularly relevant concept for refrigeration and air conditioning systems, where the risk of a significant refrigerant leak is relatively low under normal operating conditions.

Why Does This Matter for Air Conditioning and Refrigeration?

For most standard RACHP installations, the most likely classification pathway is a secondary grade of release, meaning a release of dangerous substance is not expected during normal operation, but could occur in abnormal circumstances.

Whether this results in a hazardous zone being designated depends on a number of factors, including the rate and velocity of any potential release, the degree to which that release would be diluted, and the quality and availability of ventilation.

This is where ventilation becomes critically important.

Adequate ventilation is generally taken to mean that which limits the average concentration of a dangerous substance to no more than 25% of the Lower Explosive Limit within the relevant space.

Natural ventilation is preferred wherever possible — for example, vents at both low and high level in a plant room.

Where natural ventilation is insufficient, local exhaust ventilation or mechanical general ventilation may be required.

If the assessment demonstrates that adequate ventilation is in place and the release of dangerous substance is unlikely to form a flammable mixture even in abnormal conditions, the area may be classified as non-hazardous.

But this conclusion must be reached through a proper documented assessment, not assumed.

What Needs to Be Documented?

Where a hazardous area is identified, it must be recorded in the form of a drawing.

That drawing should show the hazardous areas and the zones they fall within, the extent of those zones in both plan and elevation view, and information on the substances involved, the work activities, and the assumptions underlying the classification.

The drawing must be kept as part of the risk assessment and reviewed periodically or whenever significant changes are made.

Where hazardous areas exist, appropriate warning signs must be displayed, or the employer must demonstrate that other methods are in place to alert people to the hazardous location and any special entry requirements.

The recognised warning symbol is a yellow triangle marked with “Ex,” indicating a location where explosive atmospheres may occur.

Equipment in Hazardous Areas

If a hazardous area is identified and new equipment is to be installed within it, only equipment with a suitable protection rating for that zone may be used.

Relevant standards include BS EN 60079-14 for electrical installations in explosive atmospheres and BS EN 13463-1 for non-electrical equipment.

Using standard, unrated equipment in a classified hazardous area is a serious breach of DSEAR.

Ignition Sources Must Be Actively Managed

Part of the classification process involves identifying and controlling potential ignition sources within hazardous areas.

DSEAR and its Approved Code of Practice require consideration of heat sources, electrical sources, mechanical sources, and chemical sources of ignition.

This feeds directly into decisions about equipment specification, permit-to-work requirements, and the controls placed on activities such as hot work.

Don’t Guess — Get It Assessed

Hazardous area classification is not something that should be approached without the right technical knowledge and experience.

The consequences of getting it wrong, whether by over-classifying areas and creating unnecessary operational restrictions, or under-classifying areas and leaving ignition risk uncontrolled – can be significant.

At ESI: Fire Risk Assessment Surrey, our assessors have the knowledge and experience to carry out full DSEAR assessments including hazardous area classification for commercial and industrial premises across Surrey.

We produce clear, compliant documentation that meets regulatory requirements and stands up to HSE scrutiny.

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Hazardous Area Classification Under DSEAR