Exhaust fans remove warm, wet, dirty, or stale air from an indoor space. They help control moisture, heat, smoke, fumes, and bad smells. They are often used in bathrooms, toilets, kitchens, workshops, shops, and factories.
An exhaust fan is also called an extractor fan in the UK and many other markets. These two terms often mean the same thing. The fan draws air from a room and sends it outside.
Exhaust fans can be grouped in several ways. They can be grouped by where they are installed, how they move air, what they are used for, and how they are controlled. One fan can belong to several groups at the same time. For example, a bathroom fan can be ceiling-mounted, ducted, centrifugal, and controlled by a humidity sensor.
How Are Exhaust Fans Classified?
| Classification | Main Types |
|---|---|
| Installation position | Ceiling-mounted, wall-mounted, window-mounted, inline, and roof-mounted |
| Airflow design | Axial, centrifugal, and mixed-flow |
| Application | Bathroom, kitchen, laundry room, commercial, and industrial |
| Control method | Switch, timer, humidity sensor, motion sensor, and smart control |
Types of Exhaust Fans by Installation
1. Ceiling-Mounted Exhaust Fans
A ceiling-mounted exhaust fan is installed in or above the ceiling. The grille is visible from the room. The fan housing and motor are hidden above the ceiling.
Most ceiling-mounted fans connect to a duct. The duct carries the air to an outside wall or roof outlet. These fans are common in bathrooms, toilets, changing rooms, and small commercial spaces.
The fan in the reference image is a ceiling-mounted ducted exhaust fan. It has a square intake grille, a housing above the ceiling, and a round side outlet for the duct.
This type should not be confused with a ceiling fan. A ceiling fan moves air around a room. A ceiling-mounted exhaust fan removes air from the room.
Common names:
- Ceiling-mounted exhaust fan
- Ceiling exhaust fan
- Ceiling-mounted extractor fan
- Ceiling ventilation fan
- Recessed ceiling exhaust fan
- Ceiling-mounted ducted exhaust fan
2. Wall-Mounted Exhaust Fans
A wall-mounted exhaust fan is fitted to an outside wall. It is also called a through-wall exhaust fan.
The fan can send air straight outside through a short wall opening. Some models can also connect to a short duct. This simple airflow path often reduces pressure loss.
Wall-mounted fans are used in toilets, bathrooms, storage rooms, garages, workshops, and small factories. They are useful when there is no ceiling space for a hidden fan and duct.
The wall must have enough space for the opening. The outside outlet also needs a grille, louvre, or backdraught shutter. This part helps stop rain, insects, and outdoor air from entering the room.
3. Window-Mounted Exhaust Fans
A window-mounted exhaust fan is installed in a window frame or glass panel. It is sometimes called a glass-mounted extractor fan.
This type sends air straight outside. It does not usually need a long duct. It can be useful in older buildings where cutting a large opening in a wall is difficult.
Window-mounted fans are often used in kitchens, toilets, workshops, shops, and utility rooms. The glass or frame must be strong enough to support the fan. Glass installation should be done by a trained installer.
4. Inline Exhaust Fans
An inline exhaust fan is installed inside a duct. It is also called a duct fan, inline duct fan, or remote extractor fan.
The fan motor is placed away from the room. Only the intake grille may be visible inside. This can reduce the noise heard in the room.
One inline fan can sometimes connect to more than one intake grille. For example, it may serve two bathrooms or a bathroom and a toilet. The full system must be designed and balanced for this use.
Inline fans are useful for long ducts and systems with several bends. Centrifugal and mixed-flow designs are common because they can work against higher duct resistance.
5. Roof-Mounted Exhaust Fans
A roof-mounted exhaust fan is installed on the roof of a building. It removes air through a vertical duct or a roof opening.
These fans are common in shops, warehouses, factories, commercial kitchens, and large public buildings. They can handle larger airflow rates than most small household fans.
Roof fans may use axial or centrifugal airflow designs. Some discharge air upwards. Others discharge it downwards or to the side. The correct design depends on the air being removed and the area around the roof outlet.
Roof installation must prevent water leaks. The fan also needs protection from wind, rain, and corrosion.
Types of Exhaust Fans by Airflow Design
1. Axial Exhaust Fans
An axial fan moves air in a straight line through the fan. The air travels in the same general direction as the motor shaft.
Axial fans can move a large amount of air when there is little resistance. They are often used for direct wall exhaust, window exhaust, and short ducts.
They may lose airflow when connected to a long, narrow, or complex duct. Each bend, grille, shutter, and duct section adds resistance.
2. Centrifugal Exhaust Fans
A centrifugal fan draws air into the centre of its fan wheel. The spinning wheel then pushes the air out towards its edge.
This design can create more pressure than a basic axial fan. It is a good choice for longer ducts, smaller duct sizes, and systems with several bends.
Centrifugal fans are often used in ceiling-mounted bathroom fans, commercial ventilation systems, kitchen systems, and industrial equipment. They can also be placed inside an inline housing.
3. Mixed-Flow Exhaust Fans
A mixed-flow fan combines parts of axial and centrifugal airflow design. The air moves both forward and outwards as it passes through the fan.
Mixed-flow fans are often compact. They can provide good airflow while working against more pressure than a basic axial fan. They are common in inline duct systems.
They are useful when an axial fan is not strong enough but a larger centrifugal fan is not needed.
| Airflow Type | Main Strength | Common Uses | Main Limit |
|---|---|---|---|
| Axial | Good airflow with low resistance | Walls, windows, and short ducts | Airflow may drop in long or complex ducts |
| Centrifugal | Good pressure performance | Ceiling fans, long ducts, and commercial systems | Housing may be larger |
| Mixed-flow | Balance of airflow, pressure, and size | Inline duct systems | Usually costs more than a basic axial fan |
Types of Exhaust Fans by Application
Bathroom and Toilet Exhaust Fans
Bathroom exhaust fans remove wet air, smells, and stale air. They help reduce condensation on mirrors, walls, and ceilings. They also help control mould growth.
These fans may be installed in the ceiling, wall, window, or duct. A model installed near a shower or bath must have the correct wet-area approval and IP rating.
Useful control options include timers, humidity sensors, and continuous low-speed operation.
Kitchen Exhaust Fans
Kitchen exhaust systems remove heat, steam, smells, smoke, and cooking particles. A cooker hood or kitchen hood is usually placed above the cooking area.
A basic bathroom fan is not suitable for heavy kitchen grease. Grease can build up on the motor, fan wheel, and duct. Commercial kitchens need special hoods, grease filters, ducts, and exhaust fans.
Kitchen exhaust air should not share a duct with a bathroom fan or clothes dryer unless the system has been designed and approved for that purpose.
Laundry and Utility Room Exhaust Fans
Laundry rooms can contain warm and wet air. An exhaust fan helps control moisture from washing, drying, and indoor clothes drying.
A room exhaust fan is different from a clothes dryer outlet. A dryer needs its own duct that is suitable for hot air and lint.
Commercial Exhaust Fans
Commercial fans are used in offices, shops, hotels, schools, public toilets, changing rooms, restaurants, and storage areas.
These systems often run for longer periods than household fans. They may need larger airflow rates, stronger motors, lower energy use, and easier service access.
The fan must be selected at the real working pressure of the duct system. Its free-air airflow value does not show how it will perform after it is connected to a duct.
Industrial Exhaust Fans
Industrial exhaust fans remove heat, dust, smoke, chemical vapour, welding fumes, and process air. They are used in factories, warehouses, laboratories, paint areas, and production lines.
Industrial fans may need special materials or motors. Some systems must resist corrosion, high temperatures, sparks, or explosive gases.
A normal household or commercial exhaust fan must not be used for these risks. The full system must meet the safety rules for its site and application.
Smoke and Heat Exhaust Fans
Smoke exhaust fans form part of a building’s fire safety system. They are designed to work under set fire and heat conditions.
These products are not the same as normal ventilation fans. Their controls, power supply, ducts, and installation must follow local fire rules.
Exhaust Fan Control Options
| Control Type | How It Works | Suitable Use |
|---|---|---|
| Wall switch | The user turns the fan on and off | Simple bathrooms, toilets, and utility rooms |
| Light-linked control | The fan starts with the room light | Toilets and small bathrooms |
| Run-on timer | The fan keeps running after the switch is turned off | Bathrooms and toilets |
| Humidity sensor | The fan starts or changes speed when humidity rises | Bathrooms and laundry rooms |
| Motion sensor | The fan starts when someone enters | Public toilets and commercial spaces |
| Continuous low speed | The fan runs slowly and increases speed when needed | Homes that need steady ventilation |
| Smart control | The fan uses an app, sensor network, or building system | Modern homes and commercial buildings |
How to Choose the Right Exhaust Fan
Calculate the Required Airflow
International fan airflow is usually shown in cubic metres per hour, written as m³/h.
First, calculate the room volume:
Room volume in m³ = length × width × height
Then use the air-change rate required for the room:
Required airflow in m³/h = room volume × required air changes per hour
The correct air-change rate depends on the room, local rules, and how the space is used. A small private bathroom and a busy public toilet will not need the same airflow.
Check the Duct Resistance
A duct makes it harder for the fan to move air. Long ducts create more resistance. Small ducts, bends, filters, grilles, and backdraught shutters also increase resistance.
This resistance is measured in pascals, written as Pa. Check the fan’s performance curve at the expected pressure. Do not select a fan only from its highest airflow value.
Compare Noise Levels
Fan noise is usually shown in dB(A). A lower value normally means a quieter fan.
But the test method, fan speed, airflow, pressure, and test distance can change the result. Compare noise values that were measured under similar test conditions.
The fan may also cause vibration. Flexible connectors, correct supports, and solid installation can help reduce this noise.
Select the Correct Duct Size
Duct size is usually shown in millimetres. Common fan connections include 100 mm, 125 mm, 150 mm, and larger sizes.
A duct that is too small can reduce airflow and increase noise. Use the duct size stated by the fan maker. Keep the duct as short and straight as possible. Use smooth ducting where possible and avoid sharp bends.
Check the IP Rating
The IP rating shows how well the fan is protected from solid objects and water.
Bathrooms and other wet areas have special electrical zones. The required IP rating depends on the installation position and local electrical rules. Use a fan that is approved for the planned position.
Check Energy Use
Fan power is shown in watts. A fan with a good motor and correct controls can use less energy.
An EC motor can offer good speed control and lower energy use. Timers and humidity sensors can also stop the fan from running longer than needed.
Plan the Outdoor Outlet
An exhaust fan must send the removed air outside. It should not release wet or dirty air into a ceiling space, roof space, wall space, or another room.
The outdoor outlet should stop rain and insects from entering. A backdraught shutter can reduce unwanted airflow when the fan is off.
Allow Space for Cleaning and Service
Dust and dirt build up on the grille and fan parts. Kitchen systems can also collect grease.
The grille, fan, and duct should be easy to reach. Regular cleaning helps the fan keep its airflow and reduces noise. Always switch off the power before cleaning or service work.
What Type of Fan Is Shown in the Reference Image?
The product in the image is a ceiling-mounted ducted exhaust fan. It is also called a ceiling-mounted extractor fan.
The square grille draws air from the room. The main housing sits above the ceiling. The round side connection joins the fan to an exhaust duct. The duct then carries the air outside.
This design is often used in bathrooms, toilets, changing rooms, hotel rooms, and small commercial spaces. Its hidden body gives the room a clean appearance.
The image does not show the internal fan wheel. So it is not possible to confirm whether the fan uses an axial, centrifugal, or mixed-flow design from the outside alone.
Frequently Asked Questions
Is an extractor fan the same as an exhaust fan?
In normal use, yes. Both terms describe a fan that removes air from an indoor space and sends it outside. “Extractor fan” is more common in the UK and some other markets.
Is a ceiling exhaust fan the same as a ceiling fan?
No. A ceiling fan moves air around a room. A ceiling exhaust fan removes air through a duct or outside opening.
Does a ceiling exhaust fan need a duct?
A ceiling fan usually needs a duct or another clear path to the outside. A unit that filters air and sends it back into the room is a recirculation unit, not a true exhaust fan.
Which fan is better for a long duct?
A centrifugal or mixed-flow fan is often better for a long duct. But the final choice should be based on the airflow and pressure curve, duct size, duct length, and number of bends.
Can one inline fan serve several rooms?
Yes, some inline systems can connect to several intake grilles. The ducts must be sized and balanced correctly. The controls must also prevent air from moving between rooms.
Can a bathroom exhaust fan be installed above a shower?
Only use a model approved for that position. Check its wet-area approval, IP rating, installation instructions, and local electrical rules.
Conclusion
There are five main exhaust fan types based on installation: ceiling-mounted, wall-mounted, window-mounted, inline, and roof-mounted fans. They can also use axial, centrifugal, or mixed-flow designs.
The best type depends on the room, required airflow, duct resistance, noise level, duct size, safety needs, and control method. The fan shown in the reference image is a ceiling-mounted ducted exhaust fan. It is suitable for removing wet or stale air through a hidden ceiling duct.
