Risk analyses or ‘predictive’ aspects of comah safety reports guidance for explosives sites
The COMAH Safety Report Process for Predictive Assessment of Explosives
Step 5: Demonstration of
ALARP for the Representative Set
For all MA’s, the starting point will be to demonstrate that relevant
good practice is in place, or if not, to justify why not. Thereafter, having
characterised the risk associated with each of the MAS’s, it will be
necessary to provide clear demonstrations that they are not
Note: on HSE’s Tolerability of Risk (TOR) framework, the risks
arising to workers and members of the public from the operations
undertaken on site can fall in one of three regions; ‘broadly
acceptable’, ‘tolerable’ if ALARP and ‘unacceptable’ as set out
in the HSE publication Reducing Risks, Protecting People framework, below.
…. and have been reduced as low as is reasonably practicable (ALARP).
Note: An individual risk of death of less than 10-6 per annum is
regarded as "broadly acceptable". Individual risks above this
threshold are acceptable only if all necessary measures have been taken to
achieve a level as low as reasonably practicable. Further guidance can be
found in HSE’s/HID’s Semi Permanent Circular SPC/Permissioning/12
‘Guidance on ALARP Decisions in COMAH’.
In simple terms this ALARP demonstration should identify both ‘what
more could be done (i.e. what additional measures could be put in place) and
‘why these are not necessary ’. This exercise will:-
- require information on which processes are operated remotely, and on
the philosophy regarding remote versus non-remote manufacturing.
- require information on what corresponding controls are in place,
including the relevant good practice as found in ACOP’s, HSE guidance,
recognised standards, industry practice, which indicate the minimum
- for the "tolerable if ALARP" region, require a detailed
consideration of control measures and a rigorous demonstration that all
measures necessary have been taken to reduce the residual risk ALARP.
When no further reasonably practicable risk reduction measures can be
identified then the residual risks are ALARP.
- for the broadly acceptable region, require a demonstration based on
the adoption of relevant good practice, engineering standards,
recognised codes and guidance. Obvious and reasonably practicable risk
reduction measures should be introduced.
The ALARP demonstration described in the safety report should:
- show the link to initiators, the engineered and procedural safeguards
in place and possible additional measures to prevent, control or
mitigate the events.
- be presented on a scenario basis, with a list of further measures to
prevent or minimise / mitigate the effects of the event and associated
justification as to why the measures are not necessary. It should be
noted that it need not necessarily be quantitative, the degree of rigour
depends on the scale of the hazards and risks. Where a measure provides
benefits for several scenarios the collective benefits will need to be
- consider tolerability. This could involve using a risk matrix that has
been broadly calibrated against HSE’s risk criteria.
- as well as individual risk, consideration can be given to
multiple-fatality or group risk. The criteria derived from the HSE
– HID’s Approach to ALARP Decisions’, available from the
HSE’s web site may be appropriate.
- show that the costs (that is, the "sacrifice", whether in money,
time or trouble) in providing any further measures are ‘grossly
disproportionate’ to the benefit. When further measures can only
be implemented at costs which outweigh the benefits by a factor which is
grossly disproportionate, the risks can be said to be controlled ALARP.
- a "cost-benefit" analysis (not necessarily quantified) can be a
useful method for assessing measures to inform judgements made on
reduction of risks ALARP.
- the use of fault trees can form the basis of an acceptable ALARP
demonstration, in that it displays clear links between further measures
and how they influence the event sequence. However, this approach
represents a significant resource requirement and care is needed to
ensure that the higher risk operations are considered – prioritisation
using a risk matrix is often proportionate.
It is sometimes impractical for new Duty Holders to perform case specific
demonstrations for all identified events immediately. A more pragmatic
option in such cases is for the "representative set " of MAS’s
to be considered immediately, with the remaining risk generators being
subject to scrutiny in a rolling program, leading up to the time of the next
safety report submission. For such cases, the safety report should explain
and justify the basis of action taken and provide justifiable plans for
completion of additional assessments within a reasonable timeframe (not
later than 5 years). If the additional assessments lead to material changes
to the safety report and the demonstration of ALARP, a revision report may
be required before the next 5 yearly submission.