Some workplace substances create more than one danger. A solvent may harm health through inhalation or skin contact while also producing flammable vapour. Fine combustible dust may damage the lungs and, when dispersed in air, create an explosion risk. Assessing only one hazard can therefore leave an important part of the risk uncontrolled. COSHH and DSEAR have different purposes, but they may apply to the same activity. A coordinated approach helps employers avoid duplicated paperwork, conflicting controls and gaps between occupational-health and fire-safety arrangements.
Begin With the Task, Not the Safety Data Sheet
A safety data sheet is useful, but it does not explain exactly how a substance is used in a particular workplace. The assessment should examine storage, transfer, mixing, application, cleaning, waste handling and foreseeable spills. A suitable COSHH risk assessment considers how employees may be exposed to substances hazardous to health and what controls are required to prevent or adequately control that exposure. COSHH can cover chemicals, fumes, vapours, mists, gases and dusts, including hazardous substances produced by a work process rather than supplied in a labelled container.
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Recognise When the Same Substance Creates a Safety Risk
DSEAR focuses on dangerous substances that may cause fire, explosion, metal corrosion or risks from gases under pressure. Flammable liquids, vapours, gases and combustible dusts can therefore fall within its scope. Employers must identify these substances, examine the activities involving them and decide how to eliminate or reduce the risks.
Substances that may require both health and safety controls include:
- Solvent-based paints, adhesives, thinners and cleaning products
- Flammable gases used in production or maintenance
- Dust generated from wood, food, metal or other materials
- Aerosols and products that release hazardous vapour
- Waste or residues remaining after a process
The overlap does not mean one assessment can replace the other. It means the findings should be connected.
Use One Accurate Process Description
Separate assessors sometimes describe the same process differently. One may focus on breathing-zone exposure, while another considers release points and ignition sources. If quantities, temperatures, ventilation rates or working methods differ between documents, the controls may not align.
Create one verified process description covering the substance, quantity, physical form, frequency, equipment, people involved and possible abnormal conditions. This information can support both assessments while allowing each to address its own legal purpose.
Coordinate Control Measures at Source
The strongest control may reduce both exposure and explosion risk. Substituting a volatile solvent with a less hazardous product, enclosing a transfer process or capturing vapour at source can improve occupational hygiene while reducing the formation of a dangerous atmosphere.
HSE guidance emphasises preventing or minimising the release and spread of hazardous substances and using appropriate engineering controls rather than relying mainly on worker behaviour or personal protective equipment.
Controls must also be checked for unintended consequences. An extraction system handling flammable vapour or combustible dust may require suitable design, discharge arrangements and maintenance. Equipment selected only for exposure control may not be appropriate where an explosive atmosphere could occur.
Complete the DSEAR Assessment Around Credible Scenarios
A DSEAR assessment should examine where dangerous releases could occur, how long they may remain present and what could ignite them. This may lead to hazardous-area classification and decisions about suitable electrical or mechanical equipment. HSE describes hazardous-area classification as a way of assessing the likelihood and duration of a flammable atmosphere.
The review should consider:
- Hot surfaces, sparks, static discharge and maintenance tools
- Ventilation failure or loss of containment
- Storage quantities and separation arrangements
- Cleaning methods that may disperse combustible dust
- Emergency procedures and employee information
These findings should be shared with the people responsible for COSHH controls, maintenance and emergency planning.
Include Non-Routine Work
Routine production may be well controlled while shutdowns, cleaning, confined-space entry or contractor maintenance create different conditions. Opening equipment can release concentrated vapour or dust, while temporary tools may introduce ignition sources. Permit systems, isolation procedures and contractor briefings should refer to both sets of hazards. A control that is suitable during normal operation may not be enough during repair or decontamination.
Review Both Assessments After Change
A change in product, temperature, quantity, equipment or ventilation can affect health exposure and fire or explosion risk simultaneously. Reviews should be connected so that updating one assessment triggers consideration of the other. Incident findings, monitoring results, equipment modifications and storage changes should also be shared across safety disciplines. This prevents one team from relying on outdated assumptions.
Conclusion
Where a substance creates both health and explosion risks, COSHH and DSEAR should be treated as connected parts of one control strategy. Employers still need to address the distinct duties under each framework, but they can use a shared process description, coordinated controls and common review arrangements. This approach reduces gaps between occupational hygiene, engineering and fire safety. It also helps ensure that exposure controls do not introduce new ignition risks and that explosion precautions do not overlook the long-term health effects of everyday work.
