ISO 14520-10:2019

Overview

ISO 14520-10:2019 specifies the physical properties and system design requirements for HFC‑23 (trifluoromethane) gaseous fire‑extinguishing systems. It is a part of the ISO 14520 series and applies to HFC‑23 total‑flooding systems operating at a nominal pressure of 41 bar (non‑superpressurized) or 70 bar (nitrogen superpressurized). The standard covers extinguishant specification, physical and toxicological properties, storage container limits, fill density, required agent quantities, and personnel safety considerations.

Key topics and technical requirements

• Extinguishant specification: Minimum purity 99.6% (mol/mol); limits on acidity, water and non‑volatile residue; no visible suspended matter.
• Physical properties: Molecular mass 70, boiling point –82 °C, critical temperature 25.9 °C, vapour pressure ~41.80 bar at 20 °C. These properties feed into sizing and storage calculations.
• Agent quantity and design concentrations: Design and extinguishing concentrations for common fuels are listed (e.g., heptane extinguishment 12.6% → minimum design 16.4% by volume). A safety factor of 1.3 is applied to extinguishing concentrations to derive minimum design concentrations.
• Sizing methodology: Tabled mass‑per‑volume (m/V) data and formulas are provided to calculate agent mass required per protected volume as a function of temperature and specific volume. The specific volume S can be approximated by S = 0.3164 + 0.0012·T (T in °C).
• Storage and fill density: Maximum fill densities and container working pressures are specified (example: for 41 bar nominal, maximum fill density ~890 kg/m3; max working pressure at 50 °C ~148 bar). Exceeding fill density risks a “liquid‑full” condition and rapid pressure rise.
• Superpressurization: When used, nitrogen superpressurization requires nitrogen with moisture ≤ 60×10‑6 by mass and an equilibrium pressure of 70 (+3.5/‑0) bar at 20 °C.
• Safety and toxicology: Toxicological guidance is provided (NOAEL 30% by volume; ALC >65% for 4‑h rat exposure). Designers must assess hazards from the extinguishant, fire combustion products and breakdown products.

Practical applications

ISO 14520-10 is used to design and verify HFC‑23 total flooding systems for enclosed hazards where gaseous suppression is suitable: equipment rooms, electrical switchgear, industrial enclosures, laboratories and other spaces requiring rapid, non‑conductive suppression. The standard enables accurate agent quantity calculations, safe container selection, and compliance with personnel safety limits.

Who should use this standard

• Fire protection engineers and system designers
• Specifiers and facility safety managers
• Cylinder and system manufacturers
• Test laboratories and certification bodies
• Authorities having jurisdiction (AHJs)

Related standards

• ISO 14520‑1:2015 (General requirements) - normative reference and methodology for testing, concentrations and safety considerations.
• Other parts of the ISO 14520 series covering alternate agents and system components.

Keywords: ISO 14520-10, HFC‑23, gaseous fire‑extinguishing systems, fill density, superpressurization, design concentration, total flooding, fire protection design.