Overview
EN ISO 21805:2023 - "Guidance and recommendations on design, selection and installation of vents to safeguard the structural integrity of enclosures protected by gaseous fire‑extinguishing systems (ISO 21805:2023)" - provides practical guidance for designing pressure‑relief and post‑discharge venting for enclosures protected by fixed gaseous extinguishing systems. The document helps fulfil requirements in ISO 6183:2022 and ISO 14520‑1:2023 relating to over‑ and under‑pressurization venting and post‑discharge extraction to protect enclosure integrity and safety.
Key topics
- Scope and limitations - intended for fixed gaseous fire‑extinguishing systems and associated enclosures; clarifies use cases and safety limits.
- Safety considerations - structural safety of enclosures and personnel‑safety guidance tied to venting arrangements.
- Pressure‑relief vent design - principles for sizing, locating and mounting vents to prevent damage from positive and negative pressure transients.
- Types of vents - descriptions and selection guidance for gravity vents, counterweighted flaps, electrically‑ or pneumatically‑operated vents and accessories.
- Vent characteristics - vent efficiency, minimum opening/closing pressures, fire ratings and leakage considerations.
- Vent area calculations - methods and agent‑specific formulae for non‑liquefiable gases, CO2, and liquefiable agents; includes cascade venting and venting into adjacent enclosures.
- Post‑discharge venting - guidance for extraction and ventilation after agent discharge to remove extinguishant safely.
- Acceptance, maintenance and testing - commissioning, inspection and service recommendations to ensure ongoing compliance and performance.
- Annexes - informative guidance on deriving agent‑specific coefficients through testing and development procedures.
Applications
EN ISO 21805:2023 is intended for professionals who design, specify, install or maintain gaseous fire‑extinguishing systems and enclosure venting, including:
- Fire protection engineers and system designers
- Building services and HVAC engineers
- Installers and commissioning agents for fixed gaseous systems
- Facility managers (data centers, telecommunication rooms, engine/generator rooms, archives)
- Regulators, insurers and conformity assessment bodies
Practical uses include vent sizing for server rooms or plant enclosures, selecting suitable vent types for specific agents (e.g., CO2, IG‑type blends), designing cascade venting, and specifying post‑discharge extraction to meet structural and personnel safety requirements.
Related standards
- ISO 6183:2022 - referenced for vent area calculations and system requirements
- ISO 14520‑1:2023 - performance requirements for gaseous extinguishing systems
- EN/CEN national implementations of ISO 21805:2023 provide the harmonized route for compliance across Europe.
Keywords: EN ISO 21805:2023, pressure‑relief venting, gaseous fire‑extinguishing systems, vent area calculations, post‑discharge venting, enclosure integrity.
