ISO 24678-6:2016

Overview

ISO 24678-6:2016 - "Fire safety engineering - Requirements governing algebraic formulae - Part 6: Flashover related phenomena" defines how explicit algebraic formula sets should be documented, validated and applied for calculating flashover-related quantities (for example, the minimum heat release rate (HRR) to cause flashover) in enclosures. The standard implements general verification and validation requirements from ISO 16730‑1 and is provided as a template to ensure consistent, traceable use of algebraic fire-dynamics formulae, with a focused Annex A that presents algebraic relations for residential-size enclosures.

Key technical topics and requirements

• Template-based structure requiring explicit information on:
  • description of the physical phenomena addressed (flashover onset, hot smoke layer formation);
  • full documentation of calculation procedures and scientific basis;
  • clear statement of limitations and cautions;
  • identification and definition of input parameters with SI units;
  • defined domain of applicability supported by measurement data.
• Annex A (informative): algebraic formulae to estimate the minimum HRR to cause flashover in small/residential enclosures. These formulae are empirically derived from controlled experiments and often normalized by opening factor and enclosure surface/thermal inertia.
• Validation & applicability: requires identification of measurement datasets (with assessed quality), comparison with experimental data, and limits on direct application (e.g., naturally ventilated, moderate-volume enclosures).
• Documentation requirements: each formula presented with output description, variable definitions, scientific references or derivations, example calculations, and stated valid ranges.

Practical applications and users

Who uses ISO 24678-6:2016:

• Fire safety engineers and consultants
• Authorities having jurisdiction (AHJs), fire service personnel, code enforcers and developers
• Designers assessing fire safety of new buildings, ships or vehicles
• Practitioners validating or cross-checking numerical models (zone models, CFD)

How it is used:

• Rapid preliminary estimates of flashover thresholds (minimum HRR) to inform design decisions
• Supporting decisions on allowable combustible contents, detection and suppression requirements
• Cross-checking and bounding results from more detailed zone or CFD fire models
• Defining input parameter ranges and uncertainty for engineering calculations

Related standards

• ISO 16730‑1 (verification and validation of calculation methods)
• ISO 23932 (fire safety engineering design process)
• ISO 16735 (fire dynamics – hot layer behavior)
• ISO 13943 (fire terminology)
• ISO 5725 (measurement repeatability/reproducibility guidance)

ISO 24678-6:2016 helps ensure algebraic flashover calculations are transparent, validated and appropriately limited - enabling consistent, defensible use of simple formulae in fire safety engineering workflows.