Predictive Aspects in Your COMAH Safety Report: What MHHHRA Changes

If you run an Upper Tier COMAH site, you have to produce a COMAH Safety Report, and the Predictive Aspects section is where your risk assessment has to stand up. The CDOIF MHHHRA guidance changes what that section needs to show. This page explains how MHHHRA affects your Predictive Aspects, the less obvious knock-on to your Technical Aspects, and the practical impacts to expect, so you can see where the work is before an inspector does.

Where the Predictive Aspects sit in your COMAH Safety Report

The Predictive Aspects section is where you demonstrate the risk from your major accident hazards and show it is tolerable. It sits alongside the descriptive, technical, management (MAPP and SMS) and environmental parts of the report, but it is the section that carries the risk assessment, and it is the one MHHHRA speaks to most directly.

How MHHHRA raises the bar on your Predictive Aspects

MHHHRA is about meeting the HSE’s expectations for the COMAH risk assessment that sits underneath your Predictive Aspects. In practice that means a clearer focus on specific measures rather than generic assessment, and a demonstrable link to relevant good practice. If your Predictive Aspects currently lean on generic numbers or a broad-brush treatment, that is where the guidance will bite first.

The overlooked link: Predictive and Technical Aspects

In my experience across a range of sectors and industries, one of the most common issues the HSE raise with COMAH Safety Reports is a lack of linkage between the Predictive and Technical Aspects: the two are too often written as if they were separate exercises. MHHHRA is not guidance on writing a safety report, but because it forces a focus on specific measures and links to relevant good practice, it naturally pulls those two sections together, which is exactly the gap that tends to get flagged. Handled well, it is a chance to close a long-standing weakness rather than just add work.

What Upper Tier sites face in practice

Upper Tier sites already work to a higher risk assessment standard than Lower Tier, because of the report. But MHHHRA still lands differently for you. The main impacts I would expect:

• Your screening may throw up more major accident scenarios than your current report accounts for, which means more work.
• Your approach to the representative set of scenarios may need to change.
• Generic risk numbers, failure rates pulled from generic datasets with no link to your actual assets, are likely to be challenged.
• Expect a greater focus on demonstrating compliance with relevant good practice.
• Further risk-reduction measures are more likely to need a cost-benefit analysis to justify your position.

Common questions

Does MHHHRA tell me how to write my safety report?

No. MHHHRA is not safety-report guidance. But it shapes the risk assessment your Predictive Aspects depend on, and it helps close common gaps, including the link to your Technical Aspects.

What is the link between the Predictive and Technical Aspects?

The Predictive Aspects assess the risk; the Technical Aspects cover the engineering and controls that manage it. They should tell one story, but reports often treat them separately. A tighter focus on specific measures and relevant good practice ties them together.

Will MHHHRA mean more scenarios in my report?

It can. A fuller screening process can surface scenarios your current report does not cover.

Next step

If you want to know where your Predictive Aspects stand against MHHHRA before it becomes an inspection issue, the quickest start is my MHHHRA readiness self-assessment. Or if you would rather talk it through, book a call, with no obligation.