Most UK fire risk assessments are qualitative: they identify hazards, assess people at risk, evaluate control measures, and set out actions required to reduce risk. In more complex or higher-risk situations, a quantitative approach may be used to model fire and evacuation behaviour or to quantify risk more formally as part of fire engineering.
A quantitative fire risk assessment uses calculations or modelling to measure performance or risk levels numerically.
The key point is that UK legislation requires a suitable and sufficient assessment — it does not require a specific scoring method or a fully quantified model.
Contents
- 1 What Is a Qualitative Fire Risk Assessment?
- 2 What Is a Quantitative Fire Risk Assessment?
- 3 Qualitative vs Quantitative Fire Risk Assessment — Direct Comparison
- 4 Key Differences Between Qualitative and Quantitative Approaches
- 5 Which One Do You Need in the UK?
- 6 Do Quantitative Methods Replace a Fire Risk Assessment?
- 7 Common Pitfalls
- 8 How Fire Risk Assessments and Fire Engineering Often Work Together
- 9 Conclusion
- 10 Frequently Asked Questions
What Is a Qualitative Fire Risk Assessment?
A qualitative fire risk assessment is the most common UK approach. It is based on inspection, evidence, and professional judgement to determine whether fire risks are controlled and what actions are required.
In practice, qualitative assessments often align to recognised UK methodologies (for example, in the UK, methodologies such as PAS 79 are commonly referenced to structure a systematic, qualitative assessment approach).
Typical Qualitative Fire Risk Assessment Services
Qualitative FRA services commonly include:
- Site inspection of the premises and how it is used
- Review of ignition sources, combustibles, and fire loading
- Review of means of escape, escape route protection, signage, and emergency lighting
- Review of fire detection/alarm arrangements and testing regimes
- Review of passive fire protection (compartmentation, fire doors, fire stopping)
- Identification of deficiencies and a prioritised action plan
- Recording significant findings and review intervals
These services are typically appropriate for the majority of occupied premises, including many offices, retail units, light industrial buildings, HMOs (common parts), and common parts of blocks of flats (within scope).
What Is a Quantitative Fire Risk Assessment?
A quantitative fire risk assessment uses calculations, numerical methods, and/or modelling to estimate risk and/or fire safety performance. In the UK, “quantitative” is most often associated with fire engineering methods used to support design decisions, complex premises, or performance-based solutions.
Quantitative methods may include tools such as CFD (smoke/fire modelling) and evacuation modelling, which are commonly marketed as advanced fire engineering services.
Typical Quantitative Fire Risk Assessment and Fire Engineering Services
Quantitative / engineering-led services may include:
- Computational Fluid Dynamics (CFD) / smoke modelling to test smoke movement and tenability
- Evacuation modelling (often used alongside CFD) to evaluate evacuation performance
- ASET/RSET comparisons (available safe egress time vs required safe egress time) to support safety arguments
- Quantified/Cost benefit modelling to compare risk reduction measures
- Peer review of modelling prepared by other firms
These services are more commonly used for complex buildings, unusual layouts, large assembly spaces, high-rise or mixed-use designs, major refurbishments/change of use, or where a performance-based fire strategy is being justified.
Qualitative vs Quantitative Fire Risk Assessment — Direct Comparison
| Aspect | Qualitative | Quantitative |
|---|---|---|
| Primary Basis | Inspection and professional judgement | Calculations, modelling, numerical analysis |
| Typical Use | Most occupied premises | Complex or performance-based projects |
| Output | Action plan and significant findings | Technical modelling reports and scenario analysis |
| Legal Requirement | Required under Fire Safety Order | Not legally required unless design justification demands it |
Key Differences Between Qualitative and Quantitative Approaches
1. Purpose
- Qualitative: Manage day-to-day risk in an occupied building (hazards, people at risk, controls, actions).
- Quantitative: Provide numerical evidence to support design decisions or complex risk questions (often engineering-led).
2. Method
- Qualitative: Inspection + judgement + proportional evaluation, usually presented as findings/actions.
- Quantitative: Calculations/modelling/data, often scenario-based and assumption-driven.
3. Typical Output
- Qualitative: FRA report with significant findings and action plan.
- Quantitative: Technical reports (CFD outputs, evacuation model results, risk/cost benefit comparisons, peer reviews).
Which One Do You Need in the UK?
Under Article 9 of the Regulatory Reform (Fire Safety) Order 2005, the Responsible Person must ensure a suitable and sufficient fire risk assessment is carried out.
A quantitative approach may be appropriate where:
- The building is complex or high-risk
- There are unusual design features or non-standard evacuation strategies
- A performance-based argument is required as part of a fire strategy / Building Control route where prescriptive guidance in Approved Document B is not being followed directly.
- Engineering evidence is needed to justify or optimise design decisions (e.g., smoke control, travel distances, phased evacuation)
Do Quantitative Methods Replace a Fire Risk Assessment?
No. Quantitative modelling can support parts of fire safety decision-making, but it does not replace the broader legal requirement to assess and manage risk in an occupied building.
A suitable and sufficient assessment requires more than a risk score or a model output — it requires a clear understanding of hazards, people at risk, existing controls, and actions required.
Common Pitfalls
- False precision: numbers can look authoritative, but are heavily dependent on assumptions and inputs.
- Scope mismatch: modelling is used where simpler qualitative controls would resolve the risk.
- “Tick-box” risk scoring: scoring systems without reasoning don’t demonstrate suitability and sufficiency.
- Design vs use confusion: engineering work supports design intent, but the FRA must reflect real occupancy and management.
How Fire Risk Assessments and Fire Engineering Often Work Together
In practice, qualitative and quantitative work can complement each other:
- A qualitative FRA identifies a concern (e.g., smoke spread risk, evacuation constraints).
- Quantitative modelling tests scenarios and helps determine whether additional controls are required or which option is most effective.
This is most common where the fire strategy relies on performance-based justification.
Conclusion
Qualitative fire risk assessment is the most common UK approach and is suitable for most occupied premises when carried out competently and proportionately. Quantitative fire risk assessment methods are typically part of fire engineering and are used where complexity, design constraints, or performance-based justification requires numerical evidence.
The choice between qualitative and quantitative methods should always be proportionate to the building’s complexity, occupancy, and fire safety objectives.
In many cases, this work is undertaken to support compliance with the Building Regulations, particularly Approved Document B (Fire Safety), where a performance-based approach is being adopted
At Fire Risk Assessment Network, we provide structured, legally compliant fire risk assessments and can help clients understand when a qualitative assessment is sufficient and when specialist fire engineering support may be appropriate.
Frequently Asked Questions
Is a quantitative fire risk assessment required in the UK?
Not usually. UK duties focus on having a suitable and sufficient assessment, not a specific modelling method. Quantitative approaches are typically used for complex buildings or performance-based design questions.
What is CFD modelling in fire engineering?
CFD modelling simulates smoke and heat behaviour under fire scenarios and is often used to support complex fire strategies and evacuation safety arguments.
Can a qualitative assessment still use a risk matrix?
Yes. Many qualitative assessments use low/medium/high ratings or a matrix to support prioritisation, but the assessment still relies on professional judgement and must produce clear actions.
When should I involve a fire engineer?
Typically for complex or non-standard buildings, major refurbishments or change of use, or where engineering evidence is needed to support a fire strategy and Building Control approvals.
