Zone Model
Definition
A simplified fire model that divides a compartment into two well-mixed zones (upper hot layer and lower cool layer), predicting temperature and smoke-layer height over time. Faster to run than CFD but less spatially detailed.
- Type
- Two-zone compartment fire model
- Zones
- Upper hot layer, lower cool layer
- Predicts
- Temperature and smoke-layer height over time
- Compared to
- Faster but less detailed than CFD models
Common questions
When would an investigator choose a zone model over CFD?+
Zone models run quickly on modest hardware and suit rapid what-if checks on flashover timing or layer descent, useful during early hypothesis testing before committing to a full CFD simulation for courtroom-grade detail.
What is the main limitation of a zone model?+
It assumes each layer is uniformly mixed, so it cannot resolve local temperature gradients, plume behaviour around obstructions, or multi-room airflow the way a spatially resolved CFD model can.
Related terms
- Fire Dynamics Simulator (FDS)
- Computational fluid dynamics software developed by NIST that models fire-driven fluid flow and heat transfer. Used in landmark investigations including Station Nightclub...
- Flashover
- The near-simultaneous ignition of all exposed combustible surfaces in a compartment, occurring when the upper gas layer reaches approximately 600°C and radiative...
- Fuel-Limited Burning
- A fire regime in which oxygen is plentiful and the burning rate is controlled by the mass of combustible material available and...
- Heat Release Rate (HRR)
- The rate at which a burning material releases energy, measured in kilowatts (kW) or megawatts (MW). Measured by cone calorimetry for material...
- Ventilation-Limited Burning
- A fire regime in which the available oxygen supply, governed by opening size and position, constrains the burning rate. The fire produces...