What Is Smoke Ventilation?
Smoke ventilation is a fire-safety system designed to control and remove smoke, heat and hot gases from a building during a fire. It can use automatically opening windows, roof vents, louvres, smoke shafts, dampers or powered extract fans.
By controlling the movement of smoke, the system can help protect escape routes, improve visibility and support firefighters entering the building.
Consequently, occupants may find it more difficult to identify or use an escape route. Smoke can also make conditions more challenging for firefighters.
A smoke ventilation system creates a controlled route through which smoke and heat can leave the building. Depending on the design, this may happen naturally through an Automatic Opening Vent or mechanically through powered smoke-extract fans.
At
AK Fire Safety
,
we provide professional smoke ventilation and
Automatic Opening Vent services
throughout the United Kingdom.
What Is Smoke Ventilation in Simple Terms?
Smoke ventilation is a system that allows smoke and heat to escape from a building during a fire. It may use automatic windows, roof vents, smoke shafts, dampers or powered fans to help keep escape and firefighting routes more usable.
What Is the Purpose of Smoke Ventilation?
The purpose of smoke ventilation is to control the movement and accumulation of smoke during a fire.
A correctly designed system may help to:
- Remove smoke from communal escape routes
- Release heat and hot gases from the building
- Improve visibility during evacuation
- Support access for firefighters
- Reduce smoke spread into protected areas
- Maintain a clearer layer of air beneath rising smoke
- Support the building’s approved fire strategy
- Coordinate smoke extraction and replacement air
However, smoke ventilation does not replace fire alarms, fire doors, compartmentation, emergency lighting or other fire precautions. Instead, it forms part of the building’s overall fire-safety arrangement.
Why Is Smoke Dangerous During a Fire?
Smoke can travel through doorways, corridors, service openings and vertical shafts. Furthermore, it may spread into areas that are some distance from the original fire.
As smoke accumulates, it can:
- Reduce visibility
- Hide escape signs and exits
- Make orientation more difficult
- Enter stairwells and communal corridors
- Carry heat through the building
- Make firefighting operations more challenging
- Affect occupants beyond the immediate fire area
Therefore, many buildings use smoke-control systems to support protected escape and firefighting routes.
Smoke Ventilation Must Be Designed for the Building
Opening an ordinary window does not automatically create an effective smoke-control system. Vent size, position, airflow, replacement air, control logic and the building layout must all be considered.
How Does Smoke Ventilation Work?
Although every system is different, automatic smoke ventilation normally follows a clear operating sequence.
Smoke Is Detected
A smoke detector identifies smoke within a protected corridor, lobby, stairwell or another designated area.
A Signal Reaches the Control Panel
The detector or fire alarm interface sends an activation signal to the smoke-control panel.
The System Selects the Correct Equipment
The panel follows its programmed cause-and-effect sequence and identifies which vents, dampers or fans should operate.
Vents or Dampers Open
Electric actuators open the designated windows, roof vents, louvres or smoke-shaft dampers.
Fans Start Where Required
In a mechanical system, powered fans start and extract smoke through shafts or ductwork.
Replacement Air Enters
A separate inlet may open so that fresh air can replace the smoke being removed from the building.
What Are the Main Types of Smoke Ventilation?
Smoke ventilation systems are generally divided into natural, mechanical and pressure-differential arrangements.
| System Type | How It Works | Typical Equipment |
|---|---|---|
| Natural smoke ventilation | Uses the buoyancy of hot smoke and natural airflow to move smoke outside. | Automatic windows, roof vents, louvres, smoke shafts and air inlets. |
| Mechanical smoke extraction | Uses powered fans to draw smoke from the protected area. | Extract fans, dampers, smoke shafts, ducts and control panels. |
| Pressure-differential system | Uses pressure differences to resist smoke entering protected spaces. | Supply fans, pressure sensors, relief vents and automatic controls. |
| Hybrid smoke control | Combines natural and mechanical smoke-control methods. | AOVs, dampers, fans, shafts and replacement-air openings. |
What Is Natural Smoke Ventilation?
Natural smoke ventilation uses the tendency of hot smoke to rise. When a high-level vent opens, the smoke can travel upwards and leave the building.
Natural ventilation may use:
- Automatic Opening Vent windows
- Rooflights
- Roof-mounted smoke vents
- Automatic louvres
- Natural smoke shafts
- Stairwell vents
- Low-level replacement-air openings
The vent is normally opened by an electrical actuator after smoke detection activates the control panel.
Natural systems do not generally depend on an extract fan. However, their performance depends on the vent position, opening area, replacement air, internal temperatures and external conditions.
What Is Mechanical Smoke Ventilation?
Mechanical smoke ventilation uses powered fans to extract smoke from a building. The smoke may be drawn through a shaft, ductwork or another purpose-designed route before being discharged outside.
A mechanical system may include:
- Smoke-extract fans
- Fire-resistant ductwork
- Smoke-control dampers
- Mechanical smoke shafts
- Replacement-air openings or supply fans
- Smoke detectors
- A dedicated smoke-control panel
- Standby power arrangements
- Firefighter override controls
When smoke is detected, the correct damper may open, the extract fan may start and the replacement-air system may operate.
Mechanical smoke ventilation can provide a designed extraction rate. Nevertheless, it is normally more complex than a natural ventilation system and requires careful commissioning.
What Is an Automatic Opening Vent?
An Automatic Opening Vent, commonly known as an AOV, is an automatically operated window, rooflight, louvre, hatch or similar opening.
When smoke is detected, the AOV control panel sends a signal or electrical supply to an actuator. The actuator then opens the vent so smoke and heat can escape.
AOVs are commonly used within:
- Apartment-block corridors
- Communal lobbies
- Protected stairwells
- Natural smoke shafts
- Atriums
- Warehouse roofs
- Commercial buildings
Learn more in our guide:
What Is an Automatic Opening Vent?
What Is a Smoke Shaft?
A smoke shaft is a vertical route designed to move smoke from a corridor, lobby or another protected area to the outside.
A natural smoke shaft may contain automatic dampers on each floor. When smoke is detected on one level, the damper on that level opens while dampers on unaffected floors normally remain closed.
At the same time, a vent at the head of the shaft opens. Smoke can then move through the shaft and leave the building.
A mechanical smoke shaft operates in a similar way but uses powered extract fans to move the smoke.
Smoke Shaft Dampers Must Follow the Correct Sequence
Opening several dampers incorrectly could affect the shaft’s performance. Therefore, the cause-and-effect programming must match the building’s approved smoke-control design.
What Is Replacement or Make-Up Air?
When smoke leaves a building, replacement air generally needs to enter. This incoming air is known as replacement air or make-up air.
It may enter through:
- An automatically opened entrance door
- A low-level louvre
- A dedicated air inlet
- An automatic window
- A mechanical air-supply system
Without sufficient replacement air, the intended airflow may be reduced. In addition, pressure differences could make doors more difficult to open in some circumstances.
Therefore, commissioning and maintenance tests should include both the smoke-exhaust equipment and its associated air inlet.
Where Is Smoke Ventilation Used?
Smoke ventilation can be used in many types of residential, commercial and public buildings.
| Building or Area | Possible Smoke-Control Application |
|---|---|
| Apartment blocks | Communal corridors, lobbies, stairwells and smoke shafts. |
| Hotels | Protected corridors, stairways, atriums and shared spaces. |
| Care homes | Smoke-control arrangements coordinated with the evacuation strategy. |
| Office buildings | Stairwells, firefighting shafts, atriums and enclosed circulation routes. |
| Warehouses | High-level natural or mechanical smoke and heat exhaust. |
| Shopping centres | Atrium ventilation, smoke reservoirs, curtains and powered extraction. |
| Schools and colleges | Protected stairways, atriums and large circulation areas. |
| Underground or enclosed car parks | Mechanical ventilation designed to control smoke and exhaust gases. |
| Industrial buildings | High-level smoke vents, powered fans and smoke reservoirs. |
However, building type alone does not determine the required system. The building layout, height, fire strategy and escape arrangements must also be considered.
How Does Smoke Ventilation Protect Escape Routes?
Smoke ventilation can help remove smoke from corridors, lobbies and stairways that occupants may need to use during an evacuation.
In an apartment block, for example, smoke may enter a communal corridor when a flat entrance door is opened. A smoke ventilation system may then open an external corridor vent or the damper leading to a smoke shaft.
Consequently, smoke can be directed away from the protected staircase and released outside.
Approved Document B explains that common corridors and lobbies in relevant residential arrangements should have a means of ventilation to control smoke and protect common stairs.
View the official
Approved Document B fire-safety guidance
.
How Does Smoke Ventilation Help Firefighters?
Firefighters may need to enter a building while smoke is still present. Therefore