Introduction
As heat pump technologies evolve, they are increasingly installed in various settings such as hospital
energy centres, plant rooms, factories, industrial complexes, office buildings, and warehouses. However,
many of these facilities inadvertently fall under the scope of the Dangerous Substances and Explosive
Atmospheres Regulations (DSEAR) due to the refrigerants used.
Modern refrigerants include A2L mildly flammable; substances (like R32) and flammable hydrocarbons
such as propane (R290). FETA notes that all refrigerants are now covered by DSEAR following a 2015
amendment—due to their flammability characteristics (ignition temperature 50°C) and the high pressures
involved in compressor systems, which could result in refrigerant leaks forming sprays rather than drips.
The presence of flammable substances, compressed gases, and ignition sources means that designers and
operators must assess and control explosion risks. This case study outlines how Orbis Environmental
supported an energy centre operating both air and water source heat pumps. Through a tailored DSEAR
assessment, hazardous area classification, and A2L standards guidance, the client achieved full
compliance—without the unnecessary cost of ATEX-rated plant room upgrades.
Site Background
The energy centre supplies heating and cooling to a campus of commercial buildings using two air source
heat pumps and one water source heat pump. Each contains a significant charge of R32 (A2L refrigerant)
and small volumes of propane within the compressor oil. The plant room also stored flammable cleaning
solvents and adhesives used for maintenance.
Although the site team understood the refrigerants were flammable, they were unsure about their legal
responsibilities under DSEAR, including:
Whether the plant room needed hazardous zoning,
If equipment should be ATEX-rated,
What control measures were necessary.
Understanding DSEAR, Hazardous Zones, and ATEX
DSEAR requires employers to eliminate or reduce the risk of fire and explosion from dangerous substances.
As per FETA guidance, all A2L refrigerants are classed as flammable gases under pressure; (H221),
meaning a DSEAR risk assessment is mandatory for any heat pump or refrigerant-based system. The
assessment must cover all substances and all tasks—installation, charging, maintenance, leak testing, and
repair.
A critical part of DSEAR is hazardous area classification. According to the HSE:
Zone 0: Explosive atmosphere continuously or for long periods.
Zone 1: Likely explosive atmosphere during normal operation.
Zone 2: Unlikely in normal operation, and if it does occur, will persist for only a short time.
These classifications determine whether electrical equipment must meet ATEX requirements. The client
wanted clarity on how these applied to their heat pump plant room.
A2L Refrigerant Standards and Compliance Options
A2L refrigerants, while only mildly flammable are still subject to DSEAR. REFCOM advises that assessments for A2L systems follow BS EN 378, taking into account:
Maximum allowable charge,
Room volume and occupancy,
System design limitations.
ORBIS also advised that compliance could be achieved via:
Gas detection and/or mechanical ventilation triggered at 20% of the Lower Flammable Limit (LFL),
Or by maintaining consistent air change rates to ensure concentrations never exceed 10% LFL.
If refrigerant concentrations remain below LFL due to effective ventilation, the area may be classified as
“No Zone”, avoiding the need for ATEX-rated equipment.
Our Approach
1. Information Gathering
We reviewed:
Plant layouts and refrigerant/oil/solvent SDSs,
Maintenance records and charging practices.
Discussions with site staff helped us understand routine tasks like brazing, pressure testing, and solvent
cleaning—each a potential release point.
2. Hazard Identification and Risk Assessment
On-site inspections identified potential release scenarios:
Refrigerant leaks from joints during normal operation,
Leaks during charging, purging, or brazing,
Vapour releases from cleaning agents.
Using BS EN 378, we determined a flammable atmosphere could only form if 100% of the refrigerant
charge leaked into an unventilated room. The room already had passive louvres, but we recommended
adding mechanical extraction triggered at 10% LFL to reduce zoning requirements.
3. Hazardous Area Classification
We conducted a classification using BS EN 60079-10-1 and HSE guidance. Our conclusions:
Inside the heat pump cabinets: Zone 2 of negligible extent, due to sealed circuits and very low leak
probability.
Within 0.6 m of cabinet vents: Zone 2 of negligible extent, based on potential for low-level localised
releases in the event of a leak.
Main plant room: No Zone, due to effective mechanical ventilation and early leak detection.
Solvent cabinet: Zone 2 within 1 m radius.
We advised relocating solvent storage to the warehouse, which offered over 2 m segregation. This
eliminated the need for ATEX-rated lights or fans in the plant room.
4. Control Measures and Options
We presented three compliance pathways:
Option 1: Enhanced Ventilation & Leak Detection (Recommended)
Gas detectors & extraction fans triggered at 20% LFL,
Refrigerant charges remain below BS EN 378 thresholds,
No ATEX equipment required.
Option 2: ATEX Zoning & Equipment Upgrades
Treat the room as Zone 2,
Upgrade to ATEX-rated lights, switchgear, fans, and housings.
Much higher cost.
Option 3: Replace R32 with Non-Flammable Refrigerant
Requires full plant redesign, new compressors, condensers, etc., Long downtime and high cost.
Considered in the Hierarchy of Controls but rejected.
We performed a full cost-benefit analysis, and the client chose Option 1.
5. Risk Assessment, RAMS, and Documentation
We developed:
A detailed DSEAR risk assessment,
Hazardous area drawings,
Safe operating procedures (SOPs) for leak detection, maintenance, and emergencies.
We also prepared RAMS for refrigerant charging and leak testing. These were accepted by the enforcing
authority without changes.
6. Client Engagement and Training
We delivered:
A half-day training session for plant operators,
A full-day session for managers and responsible persons,
A two-day DSEAR Coordinator training for the site lead.
Workshops included:
An overview of DSEAR and A2L refrigerant properties,
A matrix showing when ATEX equipment is required,
Real-world examples of ignition sources (chargers, phones, batteries, smoking) and how to avoid
introducing them.
Outcomes
Following implementation, the client organisation achieved significant and practical benefits that extended
well beyond minimum regulatory compliance:
Full compliance with DSEAR and ATEX was achieved through an approach grounded in evidence and
risk assessment—not assumption or overengineering. The outcome was a system that is legally
compliant and proportionately controlled.
Clarity around ATEX responsibilities was a critical success. Rather than simply stating what needed
to be ATEX-rated, the assessment helped the client understand why certain areas did or did not
require ATEX equipment. This demystified ATEX obligations and allowed the client to make
informed, confident decisions.
Avoidance of unnecessary zoning and costs: It was demonstrated that ATEX-rated equipment was
not required throughout the entire plant room, thanks to effective control measures like leak
detection and mechanical ventilation. This prevented the organisation from incurring major capital
expense unnecessarily.
Optional upgrades identified: While ATEX-rated equipment wasn’t legally required, the client was
still made aware of optional enhancements that could further reduce risk or improve maintenance
processes—such as using shrouded connectors, isolatable electrical points, or integrating ATEX-
rated extraction in key locations. This flexible advice increased internal trust and buy-in.
Staff preparedness and operational safety: Targeted training ensured that operators, managers,
and technical leads all understood their responsibilities, particularly around ignition control,
equipment maintenance, and leak response.
Consistency across the estate: This tailored approach provided the client with a template to apply
to other sites, improving consistency and safety standards across their wider estate.
Ultimately, this project showed that ATEX compliance doesn’t always mean heavy upgrades—it means
intelligent risk control. With ORBIS’s help, the client achieved legal compliance, operational clarity, and
practical solutions that supported safe growth.
Client Testimonial
Natalie Hurdwell, Managing Director
“We’re incredibly proud of the outcome. The client was so pleased they booked us for all other ongoing
system installations—around 11 sites across the UK. They also shared our details with manufacturers and
contractors, and we’ve since secured additional work with their wider team.
Helping clients overcome challenges—especially by walking through each available option and ensuring the
most effective choice is made—is at the core of what we do. We don’t just issue a DSEAR report and walk
away. We’re committed to becoming part of the team.”