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Types of Bathroom Extractor Fan: Axial, Centrifugal, Inline and More
Updated October 2026 · Meteor Electrical guides · 9 min read
Quick answer: The main types of bathroom extractor fan are axial, centrifugal, mixed-flow and inline. Axial fans suit short ducts through a wall, centrifugal fans push air along longer ducts, mixed-flow fans sit between the two, and inline fans fit in the duct, usually in the loft. Fans also differ by mounting (wall, ceiling or window) and control (timer, humidistat, PIR or pull cord).
Choosing between the types of bathroom extractor fan comes down to three questions: how far the air has to travel, where the fan will be mounted and how you want it to switch on. This guide explains each fan type, mounting option and control, the bathroom zone and SELV rules, and which type suits which bathroom.
If you already know the type and need help with extraction rates and sizing, read our guide on how to choose a powerful bathroom extractor fan.
In this guide
What types of bathroom extractor fan are there?
Bathroom extractor fans are grouped by how the motor and blades move air. This matters because every metre of duct and every bend adds resistance, and some fan types cope with it far better than others.
| Fan type | How it moves air | Duct run it suits | Typical use |
|---|---|---|---|
| Axial | Propeller blades push air straight through | Short: through a wall or a short ceiling duct | Small bathrooms and WCs on an outside wall |
| Centrifugal | An impeller throws air outwards at higher pressure | Longer runs with bends | Internal bathrooms, ceiling fans ducted through the loft |
| Mixed-flow | A blend of axial and centrifugal designs | Short to medium runs | Upgrading an axial fan that struggles with its duct |
| Inline | Fitted inside the duct, away from the room (often mixed-flow or centrifugal) | Medium to long runs, sometimes several grilles | Showers, en-suites, quiet installs, loft-mounted |
Axial extractor fans
An axial fan uses propeller-style blades to push air straight through the fan. It moves plenty of air when the duct is short, but its output drops quickly as resistance builds, so it is best fitted through an outside wall or with a short, straight ceiling duct.
Axial fans are compact, simple and usually the lowest-cost option. Examples include the Airflow iCON eco 15 100mm extractor fan and the Xpelair 100mm extractor fan with timer.
Centrifugal extractor fans
A centrifugal fan uses an impeller that spins air outwards, building much more pressure than an axial fan. That pressure keeps the airflow up along longer ducts with bends, which makes centrifugal fans the usual choice for internal bathrooms and ceiling fans ducted across a loft.
They are often a little bigger and dearer than axial fans, but they are far less likely to underperform once installed. Always check the fan’s performance against the length of duct you plan to use.
Mixed-flow extractor fans
A mixed-flow fan combines features of both designs, giving more pressure than an axial fan while staying compact and quiet. It is a good upgrade where an axial fan struggles with its duct. The Airflow Aventa AV100 100mm mixed-flow two-speed fan is one example.
Inline extractor fans
An inline fan fits inside the duct itself, usually in the loft, with only a grille on the bathroom ceiling. Because the motor is away from the room, inline fans are often the quietest choice and suit en-suites, showers and wet rooms. Some can extract from more than one grille.
Inline fans can be axial, mixed-flow or centrifugal inside. Options include the Airflow Aventa AV100T 100mm in-line fan with timer, the Airline 100 inline extract fan with timer and the XIMX 125mm inline mixed-flow fan. For loft ducting, see our ceiling extractor fan guide.
Wall, ceiling or window: where should the fan go?
The best position is as close as possible to the main source of steam, usually the shower or bath, and ideally opposite the door so replacement air sweeps across the room. Fit the fan high on the wall or in the ceiling, where warm, moist air collects.
| Mounting | Best for | Things to check |
|---|---|---|
| Wall | Bathrooms with an outside wall | Wall thickness and core drill size; a grille with gravity flaps outside |
| Ceiling | Fans above the shower or bath, internal bathrooms | Loft ducting, condensation, zone position, fire-rated ceilings |
| Window | Rooms where wall or ceiling ducting is impractical | Needs a hole in the glass; a sealed unit usually has to be made with one |
| Inline (in the loft) | Quiet extraction, long duct runs | Access for maintenance, isolator position, ceiling grille in the right place |
Wall-mounted fans
A wall fan through an outside wall gives the shortest possible duct, so even a small axial fan can perform well. Finish the outside with a grille or gravity shutter to stop draughts and keep birds and insects out.
Ceiling-mounted fans
A ceiling fan can sit directly above the shower, which is often the most effective spot. The duct then has to cross the loft to a roof or soffit vent, so condensation control and duct length matter much more. Our ceiling extractor fan guide covers loft ducting step by step.
Window-mounted fans
A window fan fits through a hole cut in the glass. It avoids drilling walls, but double-glazed sealed units normally have to be made with the hole in place, so it is now a less common choice than a wall or ceiling fan.
Timer, humidistat, PIR or pull cord?
The control decides when the fan runs. A fan that only runs while the light is on often stops before the steam has cleared, so most bathrooms benefit from an overrun timer or a humidistat.
| Control | How it works | Best for |
|---|---|---|
| Overrun timer | Starts with the light switch and runs on for a set time after it is switched off | Most family bathrooms and windowless rooms |
| Humidistat | Starts and stops automatically as the humidity changes (usually with a timer too) | En-suites, rentals, rooms where the fan gets forgotten |
| PIR | A motion sensor starts the fan when someone enters, then a timer runs it on | WCs, cloakrooms and commercial washrooms |
| Pull cord | The user switches the fan on and off with a cord on the fan | Simple installs where the fan is controlled separately from the light |
| Continuous running | Runs at a low trickle speed all the time and boosts when needed | Airtight homes and bathrooms that need constant ventilation |
Some fans take plug-in control modules. For example, the Airflow iCON range has an iCON timer module and an iCON humidity and timer module, so you can choose the control to suit the room.
Pro tip: A fan with an overrun timer needs a permanent live, a switched live and a neutral. That usually means 3 core and earth from a triple-pole fan isolator to the fan. See our guide to 3 core and earth vs twin and earth.
Bathroom zones, IP ratings and SELV fans
BS 7671 Section 701 divides a bathroom into zones based on how close they are to water. In Ireland, I.S. 10101 uses the same approach. Zone 3 no longer exists: it was removed from the Wiring Regulations in 2008, so anywhere beyond zone 2 is simply outside the zones.
| Zone | Where it is | What the fan needs |
|---|---|---|
| Zone 0 | Inside the bath or shower tray | Not a place for an extractor fan |
| Zone 1 | Above the bath or shower tray, up to 2.25m from the floor (or the highest fixed shower head if higher) | At least IPX4 and rated by the maker for zone 1; often a 12V SELV fan |
| Zone 2 | 0.6m out from the edge of zone 1, up to the same height | At least IPX4; 230V mains fans are common here |
| Outside the zones | The rest of the bathroom | No specific IP rating in BS 7671, but use a bathroom-rated fan |
IPX4 (protection against splashing water) is the minimum in zones 1 and 2. Use IPX5 where water jets may be used for cleaning, as in some wet rooms and commercial showers. For what the numbers mean, see our IP rating guide.
What is a SELV extractor fan?
SELV stands for separated extra-low voltage. A SELV fan runs at 12V from a safety isolating transformer, so the voltage at the fan is too low to give a dangerous shock. That is why fans in zone 1, directly above the bath or shower, are often SELV 12V models. The Xpelair Simply Silent 100mm SELV bathroom fan with timer is one example.
The transformer must be fitted outside the zones, in the position the manufacturer specifies. A 230V mains fan can only go in zone 1 if the maker states that it is suitable there.
Safety: Bathroom circuits need 30mA RCD protection, and the fan isolator should be outside the zones. New circuits in bathrooms can be notifiable under Part P in England and Wales, and in Ireland the work should be done by a Registered Electrical Contractor. If you are unsure, use a qualified electrician. Read more in our bathroom electrics safety guide.
100mm or 150mm: which fan size?
Most domestic bathroom fans are 100mm (4 inch), which matches the standard 100mm duct and is enough for a typical bathroom with a sensible duct run. Larger bathrooms, wet rooms, kitchens and long ducts may need a 125mm or 150mm fan with matching ducting.
In England, Approved Document F asks for an intermittent extraction rate of at least 15 litres per second from a bathroom. What counts is the rate the fan achieves once installed, not just the figure on the box. Our powerful bathroom extractor fan guide explains the rates and how duct length affects them.
Which type of fan suits which bathroom?
Use this as a starting point, then check the fan’s performance against your duct run and its zone rating against where it will be fitted.
| Your bathroom | Fan type | Mounting | Control |
|---|---|---|---|
| Small bathroom or WC on an outside wall | Axial | Wall | Timer or PIR |
| Family bathroom, fan above the bath or shower | Axial or mixed-flow (SELV if in zone 1) | Ceiling | Timer |
| Internal bathroom with no window | Centrifugal, mixed-flow or inline | Ceiling or inline | Timer with a 15 minute overrun, or humidistat |
| En-suite next to a bedroom | Inline or a quiet mixed-flow | Inline in the loft or ceiling | Humidistat or timer |
| Wet room or large shower | Inline or centrifugal | Ceiling grille above the shower | Humidistat and timer |
| Rental property | Axial or mixed-flow | Wall or ceiling | Humidistat or continuous running |
Where the whole house suffers from condensation, not just the bathroom, positive input ventilation can work alongside your extractor fans.
Key takeaways
- The four main types of bathroom extractor fan are axial, centrifugal, mixed-flow and inline.
- Axial fans suit short ducts; centrifugal, mixed-flow and inline fans cope better with longer runs.
- Wall fans give the shortest duct; ceiling fans need careful loft ducting to a roof or soffit vent.
- Overrun timers and humidistats keep the fan running until the steam has cleared.
- Zone 3 no longer exists. IPX4 is the minimum in zones 1 and 2, and zone 1 fans are often 12V SELV.
- Approved Document F asks for at least 15 l/s from a bathroom in England.
Choosing the right type of bathroom extractor fan
The right type of bathroom extractor fan depends on your duct run, the mounting position and how you want it controlled. Choose an axial fan for short runs through a wall, a centrifugal, mixed-flow or inline fan for longer ducts, and a timer or humidistat so it runs long enough. Check the zone, use IPX4 or better in zones 1 and 2, and choose a SELV fan where it sits in zone 1 above the bath or shower.
Shop bathroom extractor fans
Axial, mixed-flow and inline fans from Airflow, Xpelair and more, plus grilles, shutters and ducting. Trade prices, next working day delivery across NI & ROI on in-stock orders before 5pm.
Shop extractor fans Shop Airflow fansNeed help choosing? Call our team on 028 8675 1515 (048 from ROI), Monday to Friday, 8am–5pm.
FAQs
What are the main types of bathroom extractor fan?
The main types are axial, centrifugal, mixed-flow and inline fans. Axial fans suit short ducts through a wall or ceiling, centrifugal fans push air along longer ducts, mixed-flow fans sit between the two, and inline fans fit inside the duct, usually in the loft, with only a grille in the bathroom.
Which type of extractor fan is best for a bathroom with no window?
A centrifugal, mixed-flow or inline fan is usually best, because an internal bathroom often needs a longer duct to reach outside. Choose a timer or humidistat model so it overruns after use. Approved Document F asks for a 15 minute overrun in rooms with no openable window.
Is a ceiling or wall extractor fan better?
Neither is better in every case. A wall fan through an outside wall has the shortest duct and is easy to fit. A ceiling fan can sit right above the shower, where the steam rises, but needs ducting through the loft to a roof or soffit vent. Choose whichever gives the shortest, straightest duct run.
Do I need a SELV extractor fan?
You need a SELV fan if it is in zone 1 and the manufacturer does not rate the mains version for that position. Many zone 1 installations use 12V SELV fans, with the transformer fitted outside the zones. Outside zone 1, a 230V mains fan with the right IP rating is normally fine.
What IP rating does a bathroom extractor fan need?
BS 7671 requires at least IPX4 for electrical equipment in zones 1 and 2, or IPX5 where water jets may be used for cleaning. Outside the zones there is no specific IP requirement, but a bathroom-rated fan is still the sensible choice because of steam and condensation.
Is a humidistat or timer extractor fan better?
A timer fan runs with the light and keeps going for a set time after it is switched off, which suits most family bathrooms. A humidistat fan starts and stops by itself as humidity rises and falls, so it suits en-suites, rentals and bathrooms where people forget to switch the fan on.