DSEAR Assessment

DSEAR Regulations

The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) makes it necessary for employers to assess the risks of dangerous substances that may cause flash fires and/or explosions in their workplace. The regulations also cover risks caused by pressurised gas cylinders and corrosive substances to metals that can attack the reinforcement steelwork of a building structure, causing collapse and injury. 

This brings UK regulations in line with the EU Chemical Agents Directive, with DSEAR enacting the physical hazards aspects of this Directive. It is necessary for these risks to be eliminated or reduced as far as is reasonably practicable. The aim is to protect anyone who may be put at risk, including employees, workplace visitors, and the public.

What is a DSEAR Assessment?

A DSEAR assessment is a risk assessment that is conducted to assess all the risks that are involved in handling, storing, and using ‘dangerous substances’ and where those activities may create a working ‘atmosphere’ which is potentially ‘explosible’. This risk assessment must include information showing that the workplace and work equipment are safe during normal operations and reasonably foreseeable abnormal operation, including maintenance activities and shutdowns.

In essence, it should cover:
  • Start up
  • Shut down
  • Normal operation
  • Abnormal operation
  • Emergency situations

Dangerous Substances

Dangerous substances are any substance that, if not properly controlled in the workplace, could cause harm to staff, visitors or the public as a result of a fire or explosion, or as a result of metal corrosion. Dangerous substances can include such things as solvents, paints and varnishes, flammable gases, dust produced by machining and sanding operations, dusts from foodstuffs, pressurised and liquefied flammable gases and substances corrosive to metal. You are likely to find one or more of these substances in most workplaces.

Some examples can include:
  • Chemicals such as cleaning products can be unstable and react when mixed with other materials.
  • Gases like methane, hydrogen, ammonia, and LPG stored in pressurised cylinders could escape and ignite, causing an explosion.
  • Dangerous liquids such as adhesives, paints, solvents, and petrol can emit flammable vapours that could explode in the air if ignited.
  • Dusts can be produced by work materials and activities such as in factories, animal feeds, sugar and flour, woodworking and coal, and can explode if ignited inside or outside of the equipment.

Hazardous Area Classification Assessment

DSEAR Compliance

To comply with DSEAR Regulations, employers need to:
  • Know which dangerous substances are within their workplace, and the risks
  • Put in place control measures to remove or reduce those risks
  • Put in place controls to reduce the effects of any potential incidents that involve dangerous substances
  • Have plans and procedures in the event of an accident, incident or emergency that involves dangerous substances
  • Ensure all employees are fully informed and trained to deal with the risks of the dangerous substances
  • Identify areas where explosive atmospheres may occur, classify the risks, including use of hazardous area classification and avoid ignition sources in those areas, such as from unprotected equipment

Frequently Asked Questions

Why Do I Need a DSEAR Risk Assessment?

Fires and explosions create harmful physical effects such as intense heat, reduction of oxygen, and overpressure effects. Substances that are corrosive to metal can cause damage to structures containing metal, which can compromise structural integrity that can lead to danger.

In order to comply with DSEAR regulations, all the risks that dangerous substances may pose must be assessed. Employers must identify any dangerous substances in their workplace, along with any work processes involving the substances. It is imperative to reduce any risks that may harm workers and members of the public.

Who Can Perform a DSEAR Assessment?

The Health and Safety Executive (HSE) states that a DSEAR Assessment must be carried out by a ‘competent person’. It is vital that DSEAR Risk Assessments are carried out by qualified, competent experts with specialist knowledge of the regulations, such as a Chartered engineer/Chemist or equivalent industry experience.

How often should a DSEAR assessment be reviewed?

The legal requirement for a DSEAR review is that it is kept ‘up to date’.  The legislation states that this applies, in particular, if there is reason to suspect it is no longer valid, and/or if there has been a significant change.

The suggestion is, therefore, that the document be reviewed at least once every three years, AND also if there have been any known changes to ‘the workplace, work processes, or organisation of the work undergoes significant changes, extensions or conversions’.

Our DSEAR Assessments Include:

When we perform a DSEAR assessment, this usually occurs during a 1–2-day site visit, where a suitably-qualified and experienced specialist Process Safety Consultant will review your relevant management arrangements and assess the workplace/site, paying attention to storage, handling, and use of dangerous substances. This assessment is used to determine a complete review of all relevant activities and risk profile.

Members of our team shall review any relevant material safety documentation and any relevant previous or published explosion data. We often have this to hand for similar substances from our extensive experience with similar previous projects.

The next step is the review of potential ignition sources, temperatures, ventilation, and other control measures that are in place, to determine the risk profile and then create the risk assessment and hazardous area classification.

The aim is to highlight areas where the risks are not controlled to a level that is considered as low as reasonably practicable; and, where we can, to give pragmatic solutions to the issues noted.

A further aspect is to ‘include to exclude’ which is where all areas of the plant/site are reviewed, even if it is only to say that there are ‘no issues’.  At least there is then a record, for posterity, that they have been reviewed. This can be summed up in the following risk assessment hierarchical ‘Three Rules of DSEAR’.

Three Rules of DSEAR:
  1. Do not have a flammable atmosphere, but if you do…
  2. Do not ignite it, but if you do…
  3. Do not hurt anyone.
The resulting report shall include:
  • Hazardous Area Classification (HAC)
  • Identification and Evaluation of Ignition Sources
  • Basis of Safety
  • Prioritised recommendations for further action

Highly Flammable Milling Process


A company was using a bead mill for the milling of solvents and paint ‘flakes’ to create high-value products. The process of milling, using the motion of the beads, causes heat and creates a hotter solvent temperature, meaning that the flash point of the solvent is exceeded in use. The equipment was not suitable for use with a highly flammable liquid and so the process had to be stopped at regular intervals to allow the temperature to reduce.

Our consultant recommended using a chiller to reduce the temperature of the solvent as it was being heated. The company agreed with this, and also noted that the reduced temperature meant that the milling could then continue for longer, increasing throughput and profitability.

DSEAR Specialists

We have fully trained DSEAR assessors and over 40 years’ experience of working in a wide range of industries that operate with the risks of explosive atmospheres. Regarding the completion of DSEAR Assessments for our clients, we are proud to continue to satisfy the HSE of our competence. We endeavour to maintain and continually improve the quality of our staff through CPD, in order to ensure that our clients receive the highest quality DSEAR Consultancy service, and to instil your confidence that you are in the hands of safe and competent professionals.

Our consultants have, between them, undertaken a large number of incident investigations regarding DSEAR, including, unfortunately, many fatalities, both in the UK, and worldwide (where, although DSEAR does not apply, the principles do).  This includes Expert Witness work and Court Appearances, including at the Old Bailey in London! For more information about our DSEAR Assessment services, please get in touch today.

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