How to Specify a Complete AOV System: Smoke Vents, Dampers, and Control Panels

Introduction

Specifying an AOV smoke control system requires more than selecting a roof vent. The system has components — vent, damper, panel, detection — and they must work together. Get one component wrong or specify them in isolation, and the system fails at commissioning.

This guide is written for fire alarm engineers and smoke and ventilation contractors who need to specify a complete, code-compliant system and want to source all components from a single supplier without managing multiple supplier accounts.

The Four Components of a Natural Smoke Control System

1. Roof-Mounted AOV Smoke Vent

The AOV (Automatic Opening Vent) is the high-level discharge point. It sits in the roof and opens on command to exhaust smoke and hot gases from the building. In a residential stairwell or common area application, this is typically a single certified EN 12101-2 dome vent — though larger or more complex buildings may require multiple vents or powered extract instead.

Key specification parameters:

Free area (aerodynamic free area expressed in m²) — drives the system’s smoke extract capacity
EN 12101-2 : 2003 certification — mandatory for smoke control applications
Opening angle and opening time — typically 140° in under 60 seconds for compliant units
Actuator type — 24V DC actuators are standard for panel-linked systems
Non-fragile classification — required for roof safety compliance

2. Lobby Dampers

In multi-storey residential applications, lobby dampers provide floor-by-floor zoning. Each lobby has its own damper. On a fire signal, only the affected floor’s damper opens — all others remain closed. This contains the smoke to the fire floor and prevents contamination of escape routes on other floors.

Lobby dampers must be compatible with the smoke control panel. The actuator voltage, signal protocol, and fail-safe position (normally open or normally closed) must all be confirmed at specification stage.

3. Smoke Control Panel

The smoke control panel is the intelligence of the system. It receives signals from smoke detectors, determines the fire floor, commands the relevant lobby damper, and opens the AOV. It also provides:

Manual override controls for fire service use
Visual indication of system status
Interface to the fire alarm panel (typically via relay or addressable protocol)
Battery backup for sustained operation

RamSpec AOV Solutions supplies smoke control panels from Vent Trade (Vent Engineering). Panel selection must be based on the number of zones (floors), the type and number of actuators, and the interface requirements with the fire alarm system.

4. Inlet Air Provision

Natural smoke control relies on a pressure differential between the extract point (the AOV) and an inlet at low level. Without adequate inlet air, the AOV cannot extract smoke effectively.

Inlet provision options include:

Automatically opening vents at low level (windows, wall vents, door undercuts)
Dedicated inlet dampers or grilles
Makeup air from an adjacent pressurised stairwell

The inlet area must be sized to match the AOV free area — or the hydraulic design of the system. BS 7346-4 provides guidance on sizing for natural smoke control systems.

Common specification failure: the AOV is correctly specified but the inlet provision is insufficient to create the required flow. Always address inlet air as part of the system design — not as an afterthought.

Relevant Standards and Codes

A complete AOV smoke control system for a residential building in England and Wales must comply with:

Approved Document B (ADB): The Building Regulations guidance document for fire safety. Sets out where smoke control is required and references the relevant British Standards for system design.
BS 9991: Fire safety in the design, management and use of residential buildings. Primary standard for smoke control in residential applications — post-Grenfell revisions introduced significant changes to requirements for buildings over 11m and 18m.
BS 7346-4: Components for smoke and heat control systems. Provides functional recommendations for natural smoke and heat exhaust ventilation systems.
EN 12101-2 : 2003: Product standard for natural smoke and heat exhaust ventilators. Certification to this standard is mandatory for AOV units used in compliant smoke control systems.
BS EN 12101-6: Pressure differential systems. Not applicable for natural AOV systems — but relevant if the project includes a pressurised stairwell as part of the smoke strategy.

Commissioning a Multi-Component AOV System

Commissioning is where multi-component systems most commonly fail. The most frequent causes are:

Panel-to-damper wiring errors: Incorrect zone wiring causes the wrong damper to open. Each zone must be traced, labelled, and tested independently before full system test.
Fire alarm interface faults: The relay or protocol interface between the smoke control panel and fire alarm panel must be tested under simulated alarm conditions — not just continuity tested.
AOV actuator failure to communicate: Actuator voltage and polarity must match panel output. Some actuators are 24V DC positive, others negative switching — check the wiring diagrams.
Inlet air restriction: Dampers or grilles intended to provide inlet air that were closed by the main contractor after the smoke control system was installed. Always verify inlet air paths as part of commissioning.

Third-party commissioning by a specialist is required in many building control applications. Check with building control at specification stage whether commissioning certification will be required and by whom.

Single-Source Procurement from RamSpec AOV

RamSpec AOV Solutions supplies all three active components of a natural AOV smoke control system from a single online source:

AOV smoke vents: Brett Martin Mardome (EN 12101-2 certified), Ventlux
Lobby dampers and control panels: Vent Trade (Vent Engineering)
Rooflights: Brett Martin, Ventlux, Vent Trade

All orders are pro-forma, fulfilled direct from the relevant supplier to site, with a 10–15 working day lead time.

There is no minimum order and no account opening process. Specify the components, pay online, and the order goes direct.

Browse the full range at ramspecaov.co.uk.

Planning a smoke control installation? Order all system components from ramspecaov.co.uk — AOV vents, lobby dampers, and smoke control panels, all from one place, delivered direct to site.

Summary

A complete AOV smoke control system is not a single product — it is an assembly of certified components that must be correctly specified, installed, and commissioned to perform. The four elements — AOV vent, lobby dampers, control panel, and inlet air provision — must all be addressed at specification stage.

RamSpec AOV Solutions can supply the hardware. The system design, compliance sign-off, and commissioning are the responsibility of the specifying engineer and contractor — but we can make procurement straightforward.