An extraction system that only removes air without replacing it creates negative pressure — which causes doors to stick, reduces fan performance, and can even pull in unwanted air from other spaces. This is where make-up air comes in.
Why Balance Matters
Every cubic metre of air an extraction fan removes needs to be replaced from somewhere. Without a planned make-up air source, a building draws in air through gaps, doors, and windows — often unfiltered and uncontrolled, and it makes the extraction fan work harder than it should.
Signs Your System Is Unbalanced
- Doors are difficult to open or slam shut on their own
- Extraction seems weaker than the fan's rated output
- Noticeable draughts from unexpected gaps
- Fan runs constantly at high speed without achieving expected results
Getting the Balance Right
For most single-fan workshop or kitchen setups, ensuring there's a passive air inlet (a louvre, vent, or gap under a door) sized appropriately for the fan's output is often enough. Larger sites may need a dedicated supply air system to match extraction rates.
If your extraction fan seems underpowered despite being correctly sized, an unbalanced make-up air supply is one of the most overlooked causes — worth checking before assuming the fan itself is the problem.
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Canopy Man manufactures commercial kitchen extraction in Birmingham and delivers across England & Wales. Call 07458 148000 / 07300 815599 or contact us for advice or a quote.