When Is Fire & Smoke CFD Analysis Actually Needed?

Author: Fikret KIR – FK SOLUTION Fire Engineering & Consultancy

Content type: English Knowledge Centre / Technical Article

Fire CFD is often associated with visually impressive smoke simulations, but the engineering value is much more specific. A good CFD study starts with a question and an acceptance criterion: Will the smoke-control system maintain a tenable escape route? Will an atrium maintain a smoke layer above occupants? Will a jet-fan arrangement move smoke away from fire-fighter access?

CFD should not be used automatically on every project. Where prescriptive calculations and standard design methods clearly demonstrate compliance, simulation may add little value. It becomes useful when geometry, smoke movement, interaction between systems or performance-based justification requires more detailed analysis.

Projects Where CFD Often Adds Value

• Atria
• Large assembly spaces
• Car parks with jet-fan smoke control
• Industrial halls
• Complex natural smoke ventilation
• Performance-based alternative designs
• BESS / technical enclosures requiring gas or smoke dispersion analysis

Define Acceptance Criteria Before the Model

• Visibility
• Temperature
• Smoke layer height
• Gas concentration where relevant
• Door/escape-route conditions
• Time-based tenability

ASET and RSET Are Different Questions

Available Safe Egress Time (ASET) describes the time until conditions become untenable under the defined criteria. Required Safe Egress Time (RSET) describes the time occupants need to detect, respond and move to safety. CFD usually informs the ASET side; evacuation analysis is a separate input.

Model Quality Depends on Inputs

• Design fire / HRR
• Fire growth curve
• Geometry
• Mesh resolution
• Ventilation boundary conditions
• Door states
• Material thermal properties
• Sprinkler interaction assumptions
• Wind for external/open scenarios
• Sensitivity analysis

Frequently Asked Questions

Does CFD predict exactly what will happen in a real fire?

No. It predicts the defined scenario under the model assumptions. Uncertainty and limitations must be reported.

Can CFD replace a fire code?

No. It can support a performance-based justification where the regulatory framework allows it.

Is evacuation modelling always required with CFD?

Not always. It depends on the engineering question; where life-safety timing is evaluated, RSET should be addressed appropriately.