What is MHHHRA?
MHHHRA, or Major Hazard Human Harm Risk Assessment, is a new guidance framework developed by the Chemical and Downstream Oil Industries Forum (CDOIF) to support the assessment of major accident hazard risks to people.
Although formal publication is still anticipated, expectations are already emerging through Health and Safety Executive discussions, industry forums, and COMAH Safety Report pre-receipt meetings.
For many operators, MHHHRA is expected to become the benchmark for demonstrating that major accident hazard risks to people have been assessed comprehensively and that risks have been reduced to As Low As Reasonably Practicable (ALARP).
Why does this guidance matter?
MHHHRA provides a structured methodology for assessing the risks associated with major accident hazards and demonstrating that suitable controls are in place.
In many ways, MHHHRA is expected to play a similar role for human harm risk assessment as the CDOIF Environmental Risk Tolerability guidance currently plays for environmental MATTE assessments within COMAH Safety Reports.
As regulatory expectations continue to evolve, organisations may increasingly need to demonstrate that their Safety Reports align with the principles outlined in MHHHRA.
Who does MHHHRA apply to?
MHHHRA is particularly relevant to operators of COMAH establishments who are required to demonstrate that major accident hazards have been identified, assessed, and managed appropriately.
It is likely to be especially important for Upper Tier COMAH sites preparing:
- New COMAH Safety Reports
- Safety Report revisions
- Safety Report updates following significant changes
- Demonstrations of risk tolerability and ALARP
What does MHHHRA require?
MHHHRA follows a structured process consisting of four key stages:
Identification
The first stage involves identifying the full range of major accident hazards across the establishment.
This typically includes:
- Developing a screening table of all major accident hazards
- Grouping hazards into intuitive operational areas
- Identifying representative scenarios
- Rationalising similar hazards where appropriate
The aim is to ensure all relevant major accident hazards are captured within a clear and auditable framework.
Analysis
The analysis stage develops a detailed understanding of each representative scenario.
This may include:
- Consequence modelling
- Identification of major accident hazard outcomes
- Development of fault trees and event trees
- Review of initiating events
- Assessment of existing safeguards
- Identification of applicable good practice
- Estimation of scenario likelihood
- Identification of risk gaps
This stage often represents the largest body of work within a MHHHRA assessment.
Assessment
The assessment stage moves beyond individual scenarios and considers cumulative risk.
This includes:
- Assessing the combined impact of all major accident hazard scenarios
- Evaluating risks to different job roles
- Considering on-site personnel exposure
- Considering off-site population exposure
- Reviewing societal and individual risk levels
The objective is to understand the overall risk profile of the establishment rather than simply reviewing hazards in isolation.
Further Measures and ALARP
The final stage focuses on risk tolerability and determining whether additional risk reduction measures are required.
This includes:
- Assessing whether risks are ALARP
- Reviewing cumulative risk findings
- Identifying further measures where necessary
- Demonstrating that risk reduction decisions are proportionate and justified
This stage supports the overall demonstration that major accident risks are being managed effectively.
Why are organisations talking about MHHHRA now?
Although the guidance has not yet been formally published, industry awareness is increasing rapidly.
Operators are recognising that MHHHRA may significantly influence future COMAH Safety Report expectations and that preparation now can reduce challenges later.
Developing the information required for a MHHHRA assessment can involve:
- Hazard identification studies
- Consequence modelling
- Risk assessments
- Fault tree analysis
- Event tree analysis
- ALARP demonstrations
- Safety management system reviews
Many of these elements already exist within organisations but may need to be consolidated into a coherent MHHHRA framework.
What challenges do companies face when preparing a MHHHRA?
One of the biggest challenges is bringing together multiple process safety studies and datasets into a single structured assessment.
Common difficulties include:
- Identifying representative scenarios
- Demonstrating cumulative risk
- Organising large volumes of information
- Establishing consistent methodologies
- Demonstrating ALARP clearly
- Identifying and addressing risk gaps
A structured approach can significantly improve efficiency and consistency.
How can OTECSA help with MHHHRA?
At OTECSA Consulting Ltd, we are already supporting clients in developing MHHHRA-compliant assessments.
Our process safety specialists can assist with:
- Major accident hazard identification
- Consequence modelling
- HAZOP studies
- LOPA studies
- Risk assessments
- Fault tree analysis
- Event tree analysis
- COMAH Safety Reports
- ALARP demonstrations
By combining these disciplines, we help clients develop a clear and defensible MHHHRA that aligns with emerging expectations.
What should organisations do next?
If your site falls under COMAH regulations, now is the ideal time to review how your current major accident hazard assessments align with the emerging MHHHRA framework.
Early preparation can help identify information gaps, reduce future workload, and improve confidence that your Safety Report will meet evolving regulatory expectations.
If you would like to discuss MHHHRA, COMAH Safety Reports, or major accident hazard risk assessments, get in touch with our team to find out how we can help.