Extractor Fan

A mechanical ventilation fan installed in kitchens, bathrooms, and utility rooms to remove excess moisture, odours, and stale air.

An extractor fan is an electrically powered fan that draws moist, stale, or contaminated air out of a room and expels it outside, either through an external wall or via ducting to a roof vent. Extractor fans are a building regulations requirement in bathrooms, shower rooms, and kitchens in most countries, and they play a vital role in preventing damp, condensation, and mould.

Where extractor fans are required

  • Bathrooms and shower rooms — to remove steam and moisture from bathing and showering
  • Kitchens — to remove cooking fumes, steam, and grease-laden air (a cooker hood with extraction serves the same purpose)
  • Utility rooms — where a tumble dryer or washing machine produces moisture
  • En-suites and wet rooms — especially critical in these smaller, often windowless spaces where moisture concentrates quickly

Types of extractor fan

  • Axial fans — the most common type, mounted in a wall or window. Simple and affordable, effective where the duct run to the outside is short (under 1.5 m)
  • Centrifugal (inline) fans — mounted within the ducting rather than in the room, capable of moving air through longer duct runs. Quieter in the room itself since the motor is remote
  • Ceiling-mounted fans — extract air into the loft space and then outside via a duct. Common in bathrooms where an external wall is not accessible
  • Continuous mechanical extract ventilation (MEV) — a whole-house system with a central fan extracting from multiple rooms simultaneously

Extraction rates

Building regulations specify minimum extraction rates:

  • Bathroom — 15 litres per second (l/s)
  • Kitchen — 30 l/s (adjacent to the hob) or 60 l/s if the extractor is elsewhere in the room
  • Utility room — 15 l/s

Timer and humidity controls

Modern extractor fans often include:

  • Overrun timer — the fan continues running for a set period (typically 15-20 minutes) after the light is switched off, ensuring moisture is fully cleared
  • Humidity sensor — the fan activates automatically when it detects high moisture levels, then switches off when humidity returns to normal
  • Pull-cord or switched — manual control, sometimes required in addition to automatic controls

Practical tip

When planning a bathroom renovation, discuss extractor fan specification with your contractor during the first fix stage, as wiring and ducting need to be in place before walls and ceilings are closed up. A quiet fan with a humidity sensor and overrun timer is worth the small extra cost — a noisy or ineffective fan often gets switched off by residents, leading to damp problems.