ISO 24678-9:2022

Overview

ISO 24678-9:2022 - part of the ISO 24678 series on fire safety engineering - defines the requirements governing the application of explicit algebraic formula sets used to calculate specific characteristics of an ejected flame from an opening. The standard is intended for qualified fire safety practitioners and focuses on how to describe the physical phenomena, select input parameters, define domains of applicability and document calculations when using algebraic (closed‑form) formulae rather than full numerical models.

Key topics and requirements

• Scope and purpose: Requirements for applying algebraic formulae to calculate ejected‑flame characteristics (heat flux, trajectory, temperature, mass flow, etc.) from openings in flashed enclosures.
• Physical description: Identify flame regions (continuous flaming, intermittent, non‑combusting buoyant flow), influence of aspect ratio, façade, wind and enclosure properties.
• Calculation process: Clear procedures for deriving flame characteristics, heat flux calculation and how to combine configuration factors and atmospheric transmissivity to obtain target irradiance.
• Input parameters and symbols: Standardized definitions (e.g., aspect ratio, equivalent opening radius, neutral plane, mean temperature rise, mass flow rates) and notation are provided to ensure consistency.
• Limitations and domain of applicability: Explicit statements on when the algebraic formulae may be used (e.g., quasi‑steady ejected flames, single rectangular openings) and the model boundaries to avoid misuse.
• Example documentation and Annex A: Annex A supplies a set of formulae for heat flux from an ejected flame (single rectangular opening), a comprehensive symbol list and worked documentation examples for compliance with Clauses 4–8.

Practical applications and users

• Who uses it: Fire safety engineers, façade designers, building/ship/vehicle designers, performance‑based design specialists, regulatory authorities and consultants performing rapid consequence estimates or comparing design options.
• Why it’s useful:
  • Provides quick, repeatable estimates of heat flux and flame behavior when detailed CFD or experiments are impractical.
  • Supports performance‑based fire safety design workflows (e.g., to assess risk to adjacent targets, façade ignition, or external fire spread).
  • Helps validate preliminary designs and guides decisions before detailed numerical modelling or testing.

Related standards (if applicable)

• ISO 24678-1 - General requirements for algebraic formulae in fire safety engineering
• ISO 13943 - Fire safety vocabulary
• ISO 23932-1 - General principles of fire safety engineering (performance‑based methodology)
• Other parts of the ISO 24678 series and supporting ISO/TR documents referenced in ISO 24678-9

Keywords: ISO 24678-9:2022, fire safety engineering, ejected flame, algebraic formulae, heat flux, opening, performance-based design, façade fire, enclosure fire.