Overview
EN 15004-4:2020 is the CEN European Standard that specifies the physical properties and system design requirements for HFC‑125 gas extinguishing systems (based on ISO 14520‑8:2019, modified). It applies to fixed, total‑flooding gaseous fire‑extinguishing systems using pentafluoroethane (HFC‑125) and covers specification, usage, safety and environmental aspects for systems operating at nominal pressures of 25 bar and 42 bar (superpressurized with nitrogen).
Key topics and technical requirements
- Extinguishant specification: HFC‑125 purity ≥ 99.6 % by mass, strict limits on acidity, water and non‑volatile residue.
- Physical properties: Molecular mass 120.02, boiling point −48.09 °C, critical pressure 36.18 bar, liquid density at 20 °C ≈ 1 218 kg/m3. These properties drive storage, fill density and discharge design.
- Agent quantity and design concentrations: Tables give agent mass per protected volume (m/V) as a function of temperature and required volumetric concentration (typical design ranges 7–16 % by volume). Example reference extinguishing and minimum design concentrations: heptane (extinguish 9.3 %; minimum design 12.1 %), wood crib (extinguish 6.7 %; minimum design 11.2 %).
- Fill density and superpressurization: Maximum container fill densities are specified separately for 25 bar and 42 bar systems (Tables 6 and 7). Exceeding limits risks “liquid full” conditions with dangerous pressure rises.
- Safety of personnel: Toxicological values reported (NOAEL 7.5 % by volume, LOAEL 10 %; approximate lethal concentration ALC > 70 % for 4‑h rat exposure). Designers must consider hazards from the extinguishant, combustion products and breakdown products.
- Environmental properties: Clause added in 2020 edition addressing environmental aspects of HFC‑125 use and implications for system selection and regulatory compliance.
- Calculation aids: Specific volume of superheated vapour may be approximated by S = k1 + k2·T with k1 = 0.1825 and k2 = 0.0007 (m3/kg) for 1.013 bar and 20 °C reference.
Applications and who uses this standard
EN 15004‑4:2020 is intended for:
- Fire protection engineers and system designers calculating agent quantities, fill densities and discharge performance for HFC‑125 total‑flood systems.
- Manufacturers and installers specifying cylinder fills, superpressurization and piping layouts for 25/42 bar systems.
- Facility safety managers, insurers and authorities reviewing compliance for data centres, telecom rooms, archives and other enclosed hazards where clean‑agent total flooding is required.
- Test laboratories and certification bodies validating extinguishing and toxicity performance.
Related standards
- EN 15004‑1:2019 (Design, installation and maintenance) - normative reference.
- Other parts of EN 15004 series (e.g., Parts 2, 5–10) covering FK‑5‑1‑12, HFC‑227ea, IG gases, etc.
- ISO 14520‑8:2019 (source standard referenced and modified).
Keywords: EN 15004‑4:2020, HFC‑125, gas extinguishing systems, fixed firefighting systems, fill density, superpressurization, design concentration, total flooding, fire protection standard.
