Risk analyses or ‘predictive’ aspects of comah safety reports guidance for explosives sites
The COMAH Safety Report Process for Predictive Assessment of Explosives
Step 1: Identify all the
Major Accident Scenarios
The key task in this first part of the exercise is to ensure that all the
MAS’s are identified and recorded. To illustrate what is meant by a MAS
is, consider a car accident. The major accident (MA) is the car accident,
however, it could have resulted from a number of causes e.g. human error,
slippy road, mechanical failure, burst tyre etc. Each of these initiating
causes (or mechanisms) may lead to a similar event, a car accident, but the
outcome (or consequence) will be different and some will be more likely than
others (likelihood). In the context of the risk analysis approach described
here, the MAS includes the initiating mechanism i.e. a car accident as a
result of human error is one MAS, a car accident as a result of mechanical
failure is another etc.
The safety report’s description of the MAS identification exercise
needs to demonstrate to the Competent Authority (CA) that all MAH’s are
taken into account. As such it should be extensive, inclusive, and
transparent, otherwise doubt is placed on the analysis which follows. To do
this, the safety report should:-
- identify all the MAH’s and from these develop and list all the
potential MAS’s for each individual process/task in each building
(generic groups should only be used where the associated operations and
the consequences of the events are identical i.e. same building type,
same contents, same surrounding population etc. Otherwise the
consequences are potentially different.).
- describe appropriate, suitable, and sufficient methods that were used
to identify all events and event sequences/potential causes (including
human factors) that could potentially cause MA’s.
- show that persons of appropriate competence were used to conduct or
inform the analysis.
- describe the scope of the studies, the expertise of the team and the
results of the studies, all of which should have been recorded during
the assessment process.
- demonstrate that sufficient emphasis was given to this task.
- recognise that precautions can fail. All hazards should initially be
considered as if no precautions were in place.
- demonstrate that all MAS’s were included e.g. including very low
frequency events (some of which may be treated briefly later in the
analysis). This will help the demonstration to the CA on the rigour and
- describe the range of techniques used. These may include as
appropriate; safety reviews, checklists, studies of the causes of
previous accidents and incidents, conventional HAZOP studies, as well as
"pseudo HAZOP" studies (in which different types of energetic
stimuli provide the parameters).
Note: the level of descriptive information detailed in the Safety
Report (for all process/operations carried out) must be sufficient to
give the CA a full appreciation of the nature of the operations and all
their associated hazards.