Extractor Fan Requirements: What Every Homeowner Should Know

If you’ve ever stood in a steamy kitchen wondering why the fan can’t clear the air, you’re not alone. The problem is usually not the fan itself but that it doesn’t meet the right requirements for the space. Below we break down the most important factors – airflow, size, noise, ducting and safety – so you can choose a fan that actually works.

Airflow (CFM) – The Heart of Fan Performance

CFM stands for cubic feet per minute and tells you how much air the fan can move. As a rule of thumb, you need 100 CFM for every 10 sq ft of cooking surface. A 30‑inch hob (about 9 sq ft) therefore needs at least 90 CFM, but most experts recommend rounding up to 150 CFM for faster clearance of steam and odors. If you cook often or use a lot of pots, bump the number up by 20‑30 %.

Size and Placement – Fit the Fan to the Opening

Fans come in standard widths: 300 mm, 400 mm and 600 mm (about 12‑24 in). Measure the cut‑out opening in your cabinet or wall and pick a fan that fits snugly. A gap of more than 10 mm lets air bypass the fan, decreasing efficiency and increasing noise. Also, mount the fan as close to the cooking surface as possible – ideally within 600 mm – to capture steam before it spreads.

Don’t ignore the height of the duct. Short, straight ducts keep pressure loss low, meaning the fan can maintain its CFM rating. Every 90° bend adds roughly 30‑40 % resistance, so limit bends and keep the duct length under 3 m (10 ft) when you can.

Noise Levels – Keep the Kitchen Quiet

Noise is measured in sones. A rating of 1.5‑2.0 sones is quiet enough for most homes; anything above 3.0 can be irritating, especially in open‑plan layouts. Look for fans with insulated housings or variable‑speed motors – they let you run a lower speed for everyday cooking and ramp up when you need extra power.

Electrical and Safety Standards

All fans should be wired to a dedicated 13 A circuit with a grounded plug. In the UK, make sure the fan has a CE mark and complies with the Electrical Equipment (Safety) Regulations. If the fan is hard‑wired, it must be installed by a qualified electrician to meet Building Regulations Part F (ventilation).

For bathrooms, the fan must have an IP rating of at least IP44 to protect against moisture. Kitchen fans don’t need that high a rating but should be placed away from direct water spray to avoid short‑circuits.

Maintenance – Keep Performance Up

Even the best‑spec fan will lose efficiency if the filter gets clogged. Clean metal or charcoal filters every 2‑3 months, or more often if you cook greasy foods. Replace charcoal filters annually; metal ones can last longer but still need regular washing.

Check the duct for blockage each spring. A quick visual inspection can spot bird nests, dust buildup or crushed sections that compromise airflow.

Quick Pick‑And‑Install Checklist

• Measure the cut‑out opening – choose 300 mm, 400 mm or 600 mm fan.
• Calculate required CFM: 100 CFM per 10 sq ft of hob, add 20‑30 % for heavy use.
• Pick a fan rated ≤2.0 sones for quiet operation.
• Ensure the duct is straight, under 3 m, and uses max two bends.
• Confirm CE marking and a dedicated 13 A circuit; hire an electrician if hard‑wired.
• Plan regular filter cleaning and annual duct check.

Following these requirements will give you a fan that clears steam fast, stays quiet, and lasts for years. If you’re unsure about any step, give Bridgewater Appliance Fixers a call – we’ll help you pick the right fan and install it safely.