Evacuation modelling predicts how people move through buildings during emergencies. Understanding modelling tools and human behaviour is essential for safe design.. The Need for Evacuation Modelling When prescriptive codes provide insufficient guidance — for complex geometries, large populations, or unusual evacuation strategies — computational evacuation modelling provides quantitative evidence for design decisions. Modelling Software Pathfinder: Agent based egress simulator 3D visualisation of evacuation Continuous movement model (not nodal) Widely used in UK fire engineering STEPS (Simulation of Transient Evacuation and Pedestrian movementS): Developed by Mott MacDonald Coarse network model Suitable for large scale evacuations (stadia, transport hubs) MassMotion: Specialist pedestrian simulation tool High fidelity agent behaviour Integration with BIM models Exodus: University of Greenwich Validated against experimental data Aircraft, building, and maritime versions Human Behaviour in Fire Modelling must account for realistic human behaviour: Pre movement time — the delay before occupants begin to move (often 2 10 minutes) Route choice — people tend to use familiar routes, not necessarily the nearest exit Group behaviour — families and social groups stay together Queuing — bottlenecks at doors, stairs, and merging points Mobility impairment — reduced movement speeds, stair restrictions Counter flow — firefighters entering while occupants exit Key Outputs Output Acceptance Criteria Total evacuation time Must be less than Available Safe Egress Time (ASET) Flow rates at exits Should not exceed 80 persons/min/m for doors Stair flow rates Should not exceed 60 persons/min/m Maximum queue time Should not create untenable conditions at queue location ASET vs RSET The fundamental fire engineering equation: ASET (Available Safe Egress Time) — time from ignition until conditions become untenable (from CFD modelling) RSET (Required Safe Egress Time) — time for all occupants to reach safety (from evacuation modelling) Design requirement : ASET RSET × Safety Factor (typically 1.5 2.0) For evacuation modelling, contact Magnus Opifex. Magnus Opifex SEVEN LTD — UK's Leading Fire Safety & Fire Engineering Consultancy 🌐 magnus opifex.co.uk 📞 +44 7486 691724 ✉️ office@magnus opifex.co.uk Founders: Nicoleta Vasile, Baroness of Brattleby — CEO, Lawyer and Barrister, Legal & Administrative Director Alina — Technical Director & Expert Fire Engineer (BEng) Head Office: Ealing Cross, 85 Uxbridge Road, London W5 5BW Magnus Opifex SEVEN LTD delivers engineering led fire engineering, fire risk assessments, CFD modelling, and building safety consultancy across the United Kingdom and internationally. With over 20 years of combined experience and a UK portfolio spanning healthcare, residential and infrastructure, we bring truly engineered solutions with a personal touch. © 2026 Magnus Opifex SEVEN LTD. All rights reserved.