Ever wondered how buildings manage to stay safe during a fire, not just from flames, but from thick, dangerous smoke?

That’s where smoke ventilation systems and Automatic Opening Vents (AOVs) come in. These systems are designed to clear smoke from stairwells, corridors, and escape routes, allowing firefighters a clear path to get into the building and for use as an escape route should the fire brigade decide to evacuate the building (most residential buildings have a  “Stay Put” policy).

In simple terms, smoke ventilation systems help by preventing smokefrom  entering the staircase escape route in a building during an emergency. 

What are AOVs? They’re the collective description for automatic windows vents, louvres windows, Smoke shaft AOV doors, Smoke shaft dampers or other type panels that open up to let smoke escape when triggered by heat or smoke detection.

Smoke might seem less dramatic than flames, but it’s far more dangerous. 

Did you know over half of fire-related deaths in buildings are caused by smoke inhalation, not the fire itself?

That’s why smoke ventilation isn’t just important — it’s essential. And UK Building Regulations agree, making it a legal must-have in many buildings.

In this guide, we’ll break it all down: how the systems work, why they matter, and what you need to know as a property owner or manager, without the jargon.

Let’s clear the smoke and make it simple.

What are Smoke Ventilation Systems?

Smoke ventilation systems are life-saving mechanisms designed to provide routes that enable the removal of smoke from a building during a fire. 

Their main purpose is to keep escape routes such as stairwells and corridors clear especially due to extended escape routes used in modern buildings , so, firefighters can access the building quickly and people can evacuate to relative safety (the Staircase) and then safety outside of the building.

This is not just about safety — this is also about compliance. Many UK building regulations require these systems in multi-storey residential and commercial buildings.

So, how do they work?

A typical smoke ventilation system includes:

• Automatic Smoke detection that can sense either heat or smoke early in a fire 
• Smoke Vents or smoke extractors that open to release the smoke to atmosphere 
• Control systems that automatically or manually manage the entire operation

There are three main types of systems:

• Natural Smoke Ventilation ADB compliant 
• This includes the building’s design to enable AOV windows, AOV Roof vents, or BRE type smoke shafts that allow fires natural buoyance that is generated by the fire to push the hot gases and smoke to rise and escape naturally from the building. 
• Mechanical Smoke Ventilation Fire Engineered solutions

Pressurisation systems and depressurisation systems (Extract) This is normally found in larger residential buildings, commercial buildings such as Hospitals and commercial buildings these systems use technology to allow longer travel distances between apartments and relative safety (Staircases) for instance Great Ormand Street Hospital has an advanced control system that pressurises the staircases which prevents smoke from reaching the staircase and if it did reach the staircase it would push the smoke back as you open the doors  thus allowing an escape route with no smoke

You’ll find these systems in places like high-rise flats, underground parking garages, stairwells, and commercial buildings — anywhere smoke needs to be moved out, fast.

When seconds count, these systems save lives.

You’ll find these types systems in places such as 18m+ residential buildings, Hospitals, commercial buildings, underground parking garages, single stairwell buildings, and commercial buildings.

When seconds count, these systems can save lives.

What are AOVs?

AOVs (Automatic Opening Vents) are vents or windows that automatically open when smoke is detected, helping smoke escape from the building during a fire.

For example, it is generally considered that a staircase is a sterile area but under ADB a staircase smoke vent must open in common with a AOV activation to protect the stairwell, assuming the travel distance allows for a AOV between the flat door furthest from the staircase the AOV will open to let the smoke out — keeping the escape route clear and safe to use.

AOVs are triggered by:

• Smoke detection, which send a signal when fire conditions are detected
• Automatic systems, which open vents immediately only the fire floor will activate and the staircase in common if the AOV is a BRE type smoke shaft the top of shaft will also open in common
•  firefighters can if required reset the staircase or shut the fans off if required during there attendance
  

You’ll usually find AOVs in single staircase buildings greater than 9m in height and stalled in stairwells, corridors, lobbies, or atriums all dependent on the travel distances and other key triggers related ADB

In short?

AOVs are the building’s automatic lungs — opening up when it can’t breathe.

Why are Smoke Ventilation Systems and AOVs Important?

AOVs and Smoke Ventilation Systems are important because they play a critical role in protecting lives during a fire and ensuring buildings meet legal fire safety standards.

They are designed to automatically remove smoke and heat from escape routes, such as stairwells and corridors, and firefighters to enter the building with better visibility and allowing occupants to evacuate safely if required.

That’s where smoke ventilation systems and AOVs come in. They are essential because:

• They create safe ingress and evacuation routes by removing smoke from escape paths
• They improve visibility so people can find exits and firefighters can see what they’re doing
• They reduce the spread of smoke and toxic gases, helping prevent serious injury or death
  

From a legal standpoint, they’re also required under UK Building Regulations, which mandate smoke control measures in multi-storey buildings.

Still not sure how critical they are?

In a recent fire at a residential block in London, the AOV system activated immediately, clearing the smoke from the stairwell. Every resident evacuated safely, and firefighters said it made all the difference.

These systems aren’t just equipment — they’re life-saving infrastructure every building has in one form or another.

Overview of How Smoke Ventilation Systems Work

When a fire breaks out, every second counts. Smoke ventilation systems are built to act fast, often before you even realise there’s danger. These systems work together in a smart, connected way to clear smoke from key escape routes, giving people inside a real chance to get out safely.

Here’s how the process typically unfolds:

Step 1: Smoke is Detected

It all starts with a fire inside an apartment the residents escape but smoke follows them through their front door which does not close fully smoke enters the common area the smoke sensors are triggered. 

As soon as smoke is detected by the building’s AOV system or fire alarm system, the smoke control system is activated. 

Step 2: AOVs Automatically Open

Once the system receives a signal, the Automatic Opening Vents (AOVs) spring into action. These vents are positioned generally higher than the flat corridor doors which would be the highest point available 

and are designed to open automatically. 

Opening the vent allows smoke and hot air to rise and escape, creating a safer layer of air beneath.

Step 3: Smoke Is Extracted from the Building

With the vents open, smoke is released through natural ventilation (using the fires heat to create buoyancy pressure and airflow) or mechanical extraction (using fans or powered systems). with mechanical system it will dramatically improve visibility, and slows the spread of toxic gases, and makes it safer for fire fighters to decide if they wish people to evacuate and for other emergency teams to move in.

Step 4: The System Resets or Is Serviced

Once the emergency has passed, the system will require resetting and must be inspected and manually reset by professionals. It’s crucial to check every component

Including the AOV, the control panels, and sensors, to make sure it’s fully operational for the future.

Smoke ventilation isn’t just about removing air — it’s about buying time, saving lives, and protecting property.

Here’s the step-by-step process of how they work — simple, smart, and absolutely essential.

Key Considerations When Installing Smoke Ventilation Systems and AOVs

Installing a smoke ventilation system — especially one that includes AOVs — isn’t something you want to guess your way through. The system must be tailored to your building, fully compliant with UK regulations, and reliable in real emergencies.

Here’s what you need to consider before moving forward. There are four things (main pillar)  that you have to consider. 

1. Building Type and Layout

No two buildings are the same, which means the smoke control strategy shouldn’t be either. Whether you’re working with a high-rise residential block, a multi-level car park, or a commercial facility, the size, structure, and layout of the building will determine the type of system needed.

A small office may require a natural system, while a basement car park will likely need a powerful mechanical setup.

1. Legal and Regulatory Requirements

In the UK, smoke ventilation systems must meet the standards set out in Approved Document B, BS9991 and or BS9999 these plus BS12101 are the Smoke vetilation engineers bible for interpretation and compliance of the Building Regulations. These rules ensure that the system protects escape routes and supports firefighting access.

Compliance isn’t optional — it’s a legal obligation, and failing to meet it can result in penalties, safety risks, or even shutdowns.

1. Ongoing Maintenance and Testing

A system that isn’t tested regularly might fail when it’s needed most. All components, including AOVs, smoke detectors, and control panels, should be inspected and serviced on a scheduled basis.

You should also have a planned maintenance agreement in place to cover servicing, fault checks, and emergency support.

The SCA recent guidance document on the maintenance of Smoke vent systems is a must read when considering your smoke ventilation partner

1. Consult a Certified Specialist

Smoke ventilation systems must be designed, installed, and commissioned by experienced professionals. This ensures the setup is not only safe and effective, but also aligned with current building use and occupancy levels.

Consulting a specialist from the beginning can save time, avoid compliance issues, and most importantly — protect lives.

If you’re unsure where to start, speaking to a qualified ventilation expert is the smartest move you can make.

What Are the Main Types of AOVs?

AOVs come in several different forms, each designed to suit specific building layouts and ventilation needs. Here’s a quick look at the most common types:

AOV certified Windows

These are often installed in stairwells or corridors and open automatically to release smoke and hot air. They’re ideal for natural smoke ventilation in residential buildings and should now be compliant to BS12101pt2 “tested solution windows” all tested solution windows are tested via the testing house  and have passed the furnace test

AOV Window Louvres

These are used in general smoke ventilation applications and again compliant to BS12101 pt 2 via the testing house  and have passed the furnace test

AOV Dampers

These are a entire collection of BS12101 pt8 Louvred damper vents, these are all tested solution and come in sizes that have been tested via a testing house they feature interlocking slatted blades that open during a fire. They’re often used in smoke shafts and are tested to ensure that smoke and fire cannot break out through a non activated vent causing cross contamination.

Roof Vents

Typically found at the top of stairwells or in some cases atriums, roof vents generally open upward to let rising smoke escape vertically — perfect for use in staircases all roof vents are tested to BS12010 pt2.

Natural Smoke Shafts

These are vertical shafts normally of builders construction normally 1.5m2 as a minimum cross sectional area that pass through the building and as a rule terminate on the floor below the top floor due to wind forces they allow smoke from the fire floor to escape from the building.

Smoke shafts that meets ADB are used mostly in buildings of 18m+ and commonly single staircases

Sidewall Vents

Mounted on the side of a building (End of Corridor) or within escape routes, these vents open to release smoke horizontally. They’re often used in combination with mechanical systems for faster extraction are a cross over with AOV window louvres but a pt2 tested cladding vent does exist and can be used.

Each type serves a unique role, and choosing the right one depends on your building’s design and safety requirements.

Where Are These Systems Installed?

Smoke ventilation systems and AOVs aren’t just for large industrial complexes — they’re found in everyday buildings where fire safety is critical. These systems are typically installed in areas where smoke could build up quickly and block escape routes.

Here are some of the most common locations:

• Low rise residential (below 18m) High-rise residential (18m+)
  AOVs are used in stairwells and corridors to keep escape paths clear for residents during a fire.
• Office stairwells
  These systems help prevent smoke from spreading between floors and provide safe exit routes for employees.
  This changes according to the fire strategy normally AOV’s tend to relate to stay put buildings and commercial buildings with one staircase
• Car parks
  Mechanical ventilation is often required to extract smoke and harmful gases in underground or enclosed parking structures.
• Schools and hospitals
  Protecting vulnerable groups like children and patients means clear evacuation routes are essential in any fire event.
  

One of our clients — a housing association managing a 6-storey block of flats — had a case where an electrical fire broke out in a corridor.

The AOVs opened immediately, clearing the smoke from the stairwell within minutes. No one was harmed, and the fire brigade noted the system “worked exactly as it should.”

These systems aren’t just a box-ticking exercise — they’re real-world safety tools that can make the difference between chaos and control.

Choosing the Right System for Your Building

Not all buildings are created equal, and neither are their fire safety needs. Choosing the right smoke ventilation system depends on a range of factors, from building structure to occupancy level and fire escape design.

Here’s what to keep in mind:

• Building size and layout
  Larger or multi-storey buildings often require more advanced systems like mechanical extract units or dedicated smoke shafts.
  
• Occupancy and building use
  The number of people using the building daily — and how they move through it — will help determine system capacity and activation methods.
  
• Escape routes
  Ventilation should always support safe evacuation. Focus on protecting stairwells, lobbies, and corridors, especially in residential and commercial buildings.

Quick Tips for Building Managers

• Don’t just install what’s cheapest — install what’s right
• Review your layout and escape routes with fire consultants
• Make sure your system meets UK Building Regulations- Approved Document B
• Plan for long-term maintenance, not just the install
  

If you’re managing a commercial or residential property and want to ensure it meets all safety standards, visit the SCA smoke control association for expert guidance tailored to your building.

The right system doesn’t just tick a compliance box — it could save lives when it matters most.

Conclusion

Smoke ventilation systems and AOVs are more than just mechanical add-ons — they’re essential for protecting lives, ensuring safe evacuation routes, and keeping buildings compliant with UK fire safety regulations.

We’ve covered what these systems are, how they work, the different types available, and where they’re commonly installed. You now know that choosing the right solution depends on factors like building size, layout, and occupancy — and that proper installation and maintenance are just as important as the system itself.

Whether you’re managing a block of flats, an office building, or a public facility, having the right smoke ventilation setup in place can make the difference between a safe escape and a serious emergency.

If you’re unsure whether your current system meets legal standards or you’re planning a new install, now’s the time to take action.

Speak with a professional, get your building assessed, and make sure you’re not leaving safety to chance.

Visit FTG Ltd for expert guidance, installation, and ongoing support tailored to your building’s unique fire safety needs.

Your building deserves more than minimum compliance — it deserves complete protection.