DSEAR Risk Assessment and Hazardous Area Classification for Energy Centres | Practical Guide
Energy centres and plant rooms are commonly used to generate and distribute heat, electricity, and/or cooling. They are commonly located in residential and commercial developments (often in a basement), hospitals, universities, hotels, district heating networks, and at industrial premises.
These commonly contain air compressors, boilers, combined heat and power (CHP) units, heat pumps, and ammonia chillers. This article will focus on heat and power generation, with this article providing further information on DSEAR for heat pumps and refrigeration systems.
Does DSEAR Apply to Energy Centres?
DSEAR applies wherever dangerous substances are liable to be present in the workplace. Dangerous substances commonly found in energy centres and plant rooms include:
Natural gas
Hydrogen (or natural gas / hydrogen blends, aka Town’s Gas)
Propane or LPG
Diesel, kerosene, or fuel oil
Refrigerant gases (e.g. ammonia, R-32, R-290, etc.)
UPS or storage batteries
Solid biomass fuels
The presence of a dangerous substances does not automatically mean that hazardous zones (e.g. Zone 0, 1, 2) will be classified - this depends on a number of factors, including the pressure it is handled, the type of potential release sources present, and ventilation arrangements. Zones are determined using a process called Hazardous Area Classification (HAC).
However, a DSEAR risk assessment should be conducted wherever a dangerous substance is present.
What Does an Energy Centre DSEAR Assessment Involve?
An energy centre DSEAR assessment involves both a hazardous area classification (HAC) and a DSEAR risk assessment. A DSEAR assessment of an existing facility will involve a site visit to gather the required information for the assessment. This typically includes the type of fuels used, the fuel supply pressures, ventilation arrangements, smoke / heat / gas detection and action arrangements, provision of automatic isolation of fuel supplies, fire mitigation measures (e.g. sprinklers), and any other considerations for the risk assessment.
A DSEAR basis of safety will be determined for the energy centre - these are typically the Prevention of a Formation of an Explosive Atmosphere (e.g. by providing dilution ventilation, or rapidly detecting and isolating the gas supply to the energy centre), combined with Control of Ignition Sources (e.g. provision of suitable ATEX equipment).
If the energy centre is new, the DSEAR assessment is best carried out at the design stage so that any considerations can be highlighted and recommended actions can be incorporated into the design to avoid costly remedial actions and delays - here is where a DSEAR assessment typically fits in to the RIBA plan of work. For new facilities, a DSEAR verification is required by Regulation 7(4) of DSEAR before the facility is used for the first time. This is typically carried out at the commissioning stage and verifies that all of the required safeguards have been implemented and work as intended before the facility becomes operational.
What Standards and Guidance Can be Used for Energy Centre HAC?
The main standard for gas and vapour hazardous area classification is BS EN 60079-10-1:2021. This is an overarching standard which covers flammable gases and vapours, and also contains guidance on liquid releases (mainly pools resulting from a loss of containment).
For energy centres which use natural gas as a fuel, the Institution of Gas Engineers and Managers (IGEM) have published hazardous area classification guidance tailored to these facilities and fuels. IGEM/UP/16 Edition 2 is commonly used to design energy centres and contains a list of Yes/No questions which either allow you to classify a Zone 2 Negligible Extent (NE) for facilities which use natural gas at pressures up to 2 barg, or directs you to IGEM/SR/25 Edition 2. IGEM/SR/25 uses calculations to estimate gas release and ventilation rates to conduct the hazardous area classification. There is also a hydrogen supplement which allows it use for hydrogen and natural gas/hydrogen blends.
For liquid releases (e.g. fuel oil, diesel, or kerosene), EI 15 Edition 5 is commonly used. This provides guidance on liquid releases at pressure, and also flammable mist hazards which can arise. Research published by the HSE in 2025 (RR1207 summarises the findings) has found that diesel can create a flammable mist hazard at pressures much lower than previously thought - as low as 0.7 barg for diesel, and 1.7 barg for kerosene. This has significant implications on hazardous area classifications which may not have considered flammable mists as a credible hazard previously.
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