If you're choosing between extractor fan types for a bathroom, kitchen, or commercial space, mixed flow fans are worth understanding. They combine the best features of axial and centrifugal designs — delivering higher airflow and pressure in a compact, quiet package. This guide covers how they work, when to specify them, and which models suit residential and commercial projects.
How Mixed Flow Fans Work
A mixed flow extractor fan uses a specially designed impeller that blends two airflow principles. Axial fans pull air straight through the unit (think of a desk fan). Centrifugal fans spin air outward using curved blades, generating higher pressure. A mixed flow fan combines both — air enters axially but exits at an angle, producing more pressure than a standard axial fan without the bulk of a centrifugal unit.
This design means mixed flow fans can push air through longer duct runs without losing performance, making them ideal for installations where the ducting path is complex or extends beyond 3–4 metres.
Mixed Flow vs Axial Fans: Key Differences
| Feature | Axial Fan | Mixed Flow Fan |
|---|---|---|
| Airflow pattern | Straight through | Combined axial + centrifugal |
| Static pressure | Low | Medium–high |
| Max duct length | 1–3m typical | 3–8m+ depending on model |
| Noise level | Moderate | Lower at equivalent output |
| Size | Compact | Slightly larger |
| Best for | Short, direct ducting | Longer runs, bends, commercial |
| Typical price range | £20–80 | £50–200 |
The key advantage is pressure. If your ducting includes bends, long runs, or vertical rises, an axial fan may struggle to move enough air. A mixed flow fan maintains its rated airflow even with significant duct resistance.
When Should You Choose a Mixed Flow Fan?
Bathroom installations with long duct runs
Building Regulations Part F requires minimum extract rates of 15 l/s for bathrooms. If your ducting runs more than 3 metres or includes elbows, a mixed flow fan ensures you hit that extraction rate reliably. Read our guide on whether you need an extractor fan in your bathroom for more on the regulations.
Kitchen ventilation
Commercial kitchens require continuous extraction, and mixed flow inline fans can handle the heat and grease-laden air more effectively than basic axial units.
Loft or ceiling-mounted installations
Mixed flow fans work well mounted in loft spaces where they connect to ceiling-mounted valves below and roof terminals above — a setup that keeps noise out of the living space entirely.
Multiple room extraction
Some mixed flow inline fans are powerful enough to serve two or three rooms from a single unit, reducing costs and simplifying your ventilation system.
Commercial and industrial projects.
For offices, schools, and larger buildings where ducting runs are longer and more complex, mixed flow fans provide the pressure needed to move air reliably through the system.
Popular Mixed Flow Fans at eFans Direct
We stock mixed flow inline fans from leading UK brands including:
- S&P TD Series — the industry standard for inline mixed flow ventilation. Available in 100mm to 315mm with EC motor options for ultra-low energy consumption.
- Systemair K Series — heavy-duty mixed flow fans for commercial and industrial applications. Galvanised steel casings with backward-curved impellers.
- Vent-Axia ACM Range — compact mixed flow inline fans designed for residential and light commercial use.
All our mixed flow fans come with free UK delivery and expert advice. Not sure which size or model suits your project? Get in touch — we can help you calculate the correct airflow rate for your space.
Installation Tips
Mixed flow fans are typically mounted inline within your ducting — not on the wall or ceiling like axial fans. This means:
- Mount the fan as close to the extract point as practical to maximise suction at the room valve.
- Use rigid ducting where possible — flexible ducting adds resistance and reduces performance.
- Include anti-vibration mounts if mounting on joists or rigid structures — these fans are quiet, but vibration transfer can cause noise.
- Ensure access for maintenance — even low-maintenance EC motor fans need occasional cleaning.
Frequently Asked Questions
Are mixed flow fans quieter than axial fans?
Generally yes. Because they generate more pressure per revolution, they can run at lower speeds to achieve the same airflow, producing less noise. Many models operate below 30 dB — quieter than a whisper.
Can I use a mixed flow fan in a bathroom?
Absolutely. They're one of the best choices for bathroom ventilation, especially where the ducting route is longer than 1–2 metres. Look for models rated IPX4 or higher for moisture protection.
Do mixed flow fans use more electricity?
Not necessarily. EC motor versions are extremely energy efficient — some draw less than 10W on trickle speed. Running costs are typically £5–15 per year for continuous operation.
What size mixed flow fan do I need?
For a standard bathroom (15 l/s required), a 100mm mixed flow fan is usually sufficient. For kitchens (30–60 l/s), step up to 150mm. Commercial spaces may need 200mm+ — contact our team for sizing advice.