ISO 21927-5:2018

Overview

ISO 21927-5:2018 - "Smoke and heat control systems - Part 5: Powered smoke exhaust systems - Requirements and design" sets out requirements and design rules for powered smoke exhaust systems used to create and maintain a clear layer beneath a buoyant smoke layer in large spaces. The standard applies to spaces with a minimum ceiling height of 3 m where smoke protection is required, and it provides tables and calculation methods for designing clear layers to meet protection objectives. It also covers installation rules and system design assumptions (e.g., activation timing, air supply considerations). Certain spaces are excluded (see Key Topics).

Key topics and technical requirements

• Scope and exclusions: Applies to large-area spaces (ceiling ≥ 3 m). Design does not apply to spaces with fixed gas extinguishing systems, hazardous storage, explosion-risk areas, corridors or stairwells.
• Clear layer design: Defines the clear layer (distance from floor to smoke layer lower surface) with a minimum target height of 2.5 m; higher values may be required depending on occupancy or protected objects.
• Smoke reservoirs and barriers: Spaces must be divided into smoke reservoirs (maximum area guidance provided) using smoke barriers; maximum distance between barriers is 60 m.
• Air supply: Requires an immediate and sufficient replacement air supply near floor level when the system is activated; design limits include avoiding turbulence (replacement air velocity not greater than 1 m/s at the inlet point).
• Design assumptions: Typical design assumes early activation (automatic/manual), solid-fuel fires, a mean fire propagation rate around 10 minutes, and constraints on design fire area and smoke temperatures.
• Components and installation rules: Covers placement and types of ventilators (roof-, wall- or centrally mounted), smoke control ducts and dampers, and installation rules for reliable operation.
• Associated component standards: Ventilator testing, power supply and control equipment are covered in other parts of ISO 21927.

Practical applications

ISO 21927-5 is intended for use in the design and installation of smoke and heat exhaust ventilation systems (SHEVS) in large indoor environments, including:

• Warehouses and logistics hubs
• Shopping centres, exhibition halls and arenas
• Industrial production halls and large retail spaces The standard supports fire safety objectives such as enabling safe evacuation, improving firefighting access, limiting smoke spread, and protecting property and structure from heat and smoke damage.

Who uses this standard

• Fire safety engineers and smoke control designers
• HVAC and building services engineers
• Architects and structural designers specifying fire protection
• Contractors installing smoke exhaust systems
• Authorities having jurisdiction and code officials reviewing designs

Related standards

• ISO 21927-3 (ventilator specification/testing)
• ISO 21927-7 (smoke control ducts)
• ISO 21927-8 (smoke control dampers)
• ISO 21927-9 (control equipment)
• ISO 21927-10 (power supply)

Keywords: ISO 21927-5:2018, powered smoke exhaust systems, smoke and heat control, clear layer design, smoke reservoirs, smoke barriers, ventilators, smoke control ducts, SHEVS, fire safety design.