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DSEAR relates to a particular area of Process Safety – that of flammable atmospheres.  The principles of compliance with DSEAR are no different to compliance with any other aspect of process safety regulation.  The benefit of the DSEAR regulations is that there is great deal of written “relevant good practice” guidance available guiding us all on how to comply.

In our webpage on risk assessment we identify the 5 steps that the HSE advocates for managing process risk.  These 5 steps are also used to manage DSEAR hazards.  The steps are described below with a DSEAR assessment focus:

COMAH Consulting Ltd - DSEAR
(Dangerous Substances and Explosive Atmospheres Regulations)

inside of vessel
DSEAR Compliance Steps
DSEAR Compliance Step and Description
How do we do this?
Identify the hazards
The hazard is your flammable substances.  It might be a solid, dust, liquid, gas or vapour.  Before you can assess the risk, you need to understand the substance: Flash point, auto ignition temperature, Kst, composition, particle size etc etc…  It’s not complex; it is just laborious….we simply gather facts.  

We use the British Standard BSEN 60079 to guide us with this.
Who might be harmed and how?
We Identify all the ways and locations where the flammable substances and/or flammable atmospheres can become ignited.  Some ignition might occur in equipment, some might occur outside equipment (if there is a leak).  If it ignites how bad will it be – injuries, fatalities, pollution?

We use a variety of techniques to do this analysis depending upon the industry and how bad the consequence might be.  A motor vehicle repair garage with 100 litres of petrol warrants a much lighter approach than a chemical plant with 70T of Acetylene.  Our approach will range from using relevant good practice “templates” e.g UKLPG codes (LPG), INDG139 (batteries) through to HAZID or HAZOP.  Judging the level of proportionality required is an important benefit of our experience.
Evaluate the risks and decide on precautions

Has relevant good practice been followed?
Have the principles of inherent safety been properly implemented?
Is it reasonably practicable to eliminate or reduce some of the potential flammable atmosphere?  Is additional mitigation possible practicable e.g suppression or venting?

If the flammable atmosphere can’t be eliminated, then there is no option other than defining a hazardous area zone and to make sure that the equipment in that zone is suitable for it.  For hazardous area classification we will draw upon a variety of written relevant good practice guidance sources depending on the application e.g. EI 15, BS EN 60079, HSG176, IGEMSR/25.  All approaches require classification of zones as 0, 1 and 2 or, by default, “safe”
We will help you confirm that you have suitable procedures in place to control people activities in the hazardous (ATEX) zones.

Checking that the equipment in the zones is suitable for the zone requires suitably trained technicians.  We aren’t competent to carry out that aspect of DSEAR…..but we can guide you to organisations that are.

Record your findings

Typically, we would help you to produce a DSEAR Risk Assessment Report, Hazardous Area Calculations and Hazardous Area Drawings.

We would guide you on how to document the design, inspection, maintenance and testing records for the (“ATEX”) equipment located in hazardous zones.

Review your DSEAR assessment and update if necessary
This is normally triggered by any changes to the plant or after a certain time period has elapsed. The review process should be determined on a case by case basis and we will help you develop the necessary protocols.

COMAH Consulting Ltd is able to provide support with respect to DSEAR which can range from “hand holding” through to taking the lead and carrying out all aspects of assessment work for you.  This would include providing recommendations for compliance and for beneficial improvements.

The full requirements of DSEAR are explained in the HSE Approved Code of Practice: “Dangerous substances and explosive atmospheres” L138.  This is available for free at

Reactor vessel top, pipework and instrumentation
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