Smoke Ventilation & AOV Systems

Smoke ventilation systems, including Automatic Opening Vent (AOV) systems, are critical life safety measures designed to remove smoke and heat from buildings during a fire. In the UK, these systems are regulated by Approved Document B (ADB) of the Building Regulations and supported by standards such as BS EN 12101-2.

Purpose of Smoke Ventilation Systems

• Maintain clear escape routes for safe evacuation.
• Assist firefighters by improving visibility and reducing smoke temperature.
• Limit smoke spread and heat build-up within buildings.
• Protect property and structural integrity.

Main Types of Smoke Ventilation Systems

1. Natural Smoke Ventilation Systems

How it works:
Utilizes the natural buoyancy of hot smoke to rise and exit through automatically controlled openings like roof vents, windows, or louvres.

Pros:

• Lower installation and maintenance costs.
• No moving parts like fans — less risk of mechanical failure.
• Energy efficient.

Cons:

• Relies on effective natural airflow and building design.
• Less control compared to mechanical systems.
• Limited performance in large or complex layouts.

2. Mechanical Smoke Ventilation Systems (MSVS)

How it works:
Uses powered fans and ducts to extract smoke from common areas, typically via a dedicated shaft or riser system.

Pros:

• Suitable for tall or complex buildings (e.g., multi-storey residential).
• Provides controlled, consistent smoke extraction.
• Effective even in low wind or pressurised environments.

Cons:

• Higher cost and design complexity.
• Requires backup power (often UPS or generator).
• Regular specialist maintenance needed.

3. Automatic Opening Vent (AOV) Systems

How it works:
Connected to smoke detectors or fire alarm systems, AOVs automatically open designated vents (rooflights, windows, doors) when smoke is detected.

Pros:

• Fast automatic response to fire events.
• Complies with Part B of Building Regs.
• Widely used in stairwells, lobbies, and corridors.

Cons:

• May need integration with fire alarm or BMS systems.
• Can be affected by obstructions or poor installation.
• Requires regular function tests and inspections.

Common Applications in the UK

• Apartment block stairwells & lobbies (to maintain smoke-free escape routes).
• Commercial/industrial buildings (to reduce risk to life and property).
• Schools, shopping centres & care homes (to support safe evacuation).
• Underground car parks (mechanical systems typically used).

Relevant UK Regulations & Standards

Maintenance & Testing Overview

To comply with regulations, AOV and smoke ventilation systems must be inspected and maintained regularly by competent persons. Testing typically includes:

🔧 A maintenance logbook should be kept on-site detailing all inspections, test results, and any remedial actions taken.

Key Components of AOV Systems

• Smoke Detectors – Trigger vents when smoke is detected.
• Control Panels (AOV Controllers) – Manage activation logic and power distribution.
• Actuators/Motors – Open vents, windows, or rooflights.
• Manual Override Switches – Allow fire services or staff to trigger vents if needed.
• Power Supply – Often includes battery backup or mains-fed supply with failover.

Common System Layouts (Example)

• Stairwell Smoke Ventilation: A single roof vent opens on fire signal to keep the stairwell clear.
• Lobby Ventilation (with shaft): A vent on each floor opens along with a roof-mounted extract point.
• Mechanical Shaft System: Central fan extracts smoke via ducts from each floor; often includes dampers and fire-rated enclosures.