You switch on the bathroom extractor fan.
It makes a noise.
So it must be working.
Right?
Not necessarily.
An extractor fan's job isn't simply to spin. It needs to move moisture-laden or stale air out of the room effectively.
Over time, fans can become clogged with dust, vents can become obstructed and components can deteriorate. Sometimes the fan itself works perfectly well, but the wider ventilation arrangement prevents it from performing effectively.
Here are eight signs your bathroom or kitchen ventilation might deserve some attention.
1. The Mirror Stays Wet for a Long Time
A steamy mirror immediately after a hot shower isn't unusual.
The more useful question is:
What happens afterwards?
If the room remains heavily condensed long after you've finished, ventilation may not be removing moisture effectively enough.
Look beyond the mirror too.
Check:
Windows.
Tiles.
Ceilings.
Cold external walls.
And other surfaces where condensation repeatedly forms.
One steamy shower doesn't diagnose a ventilation problem, but persistent moisture is worth investigating.
2. Mould Keeps Returning
You clean a patch of mould.
A few weeks later, it's back.
You clean it again.
Then it returns.
Cleaning removes what you can see, but it doesn't necessarily address why the surface keeps becoming damp enough for mould to develop.
Poor ventilation can be one contributor.
Other possibilities include leaks, building defects, inadequate heating or cold surfaces, so don't automatically blame the extractor.
But if mould repeatedly appears in a moisture-heavy room, ventilation should be part of the investigation.
3. The Fan Has Become Much Noisier
You probably become accustomed to the normal sound of your fan.
So a noticeable change can tell you something.
Perhaps it now:
Rattles.
Buzzes.
Vibrates.
Grinds.
Or simply sounds considerably louder than before.
Dust and debris can contribute to problems, while worn components or mounting issues may also be involved.
Don't assume that more noise means more extraction.
Sometimes the opposite is true.
4. The Fan Runs but Seems to Move Very Little Air
This is one of the clearest distinctions between:
The fan is running
and
the ventilation is working effectively.
A fan can operate while airflow is restricted elsewhere.
Depending on the installation, possible contributors could include a dirty grille, obstructed ductwork, an external vent problem or an issue with the fan itself.
There may also be problems with how the system was originally designed or installed.
The important thing is to consider the whole airflow path—not just the visible fan on the wall or ceiling.
5. The External Vent Is Blocked
Where does the extracted air actually go?
In a properly arranged system, it needs an appropriate route to the outside.
External terminals can potentially become obstructed by dirt, debris or other problems.
If the outlet is safely visible from ground level, an obvious obstruction may be noticeable.
Don't climb onto roofs or put yourself in unsafe positions just to inspect a vent.
And don't assume every external grille belongs to the extractor you're investigating.
If access is difficult, leave the inspection to somebody equipped to do it safely.
6. Moisture Appears Somewhere Unexpected
This deserves more attention.
Suppose the bathroom itself doesn't seem particularly bad, but you discover moisture around a loft space or another area near the ventilation route.
The issue might not be the fan's extraction rate at all.
Ducting problems can potentially allow moisture to end up where it shouldn't.
That's different from ordinary bathroom condensation and may require the ventilation route to be inspected properly.
Extracting moist air from the bathroom is only useful if that air is being taken to the appropriate destination.
7. Kitchen Smells Linger for Hours
Kitchen ventilation has a different job from bathroom extraction, but similar clues can appear.
Cooking smells that remain for a long time may suggest ventilation isn't performing as effectively as expected.
However, kitchen extractor arrangements vary considerably.
Some cooker hoods extract air outside.
Others recirculate air through filters back into the room.
Those systems don't operate in the same way.
If you have a recirculating hood, filter condition becomes particularly important.
Before assuming something is broken, establish what type of system you actually have.
8. You Can't Remember the Last Time It Was Cleaned
Extractor fans move air.
Air carries dust.
Kitchen systems may also encounter grease.
Over time, that means components can become dirty.
Cleaning requirements vary by product, so follow the manufacturer's instructions rather than spraying cleaning products into electrical equipment.
Accessible covers or filters may be designed for routine maintenance.
Other components shouldn't be dismantled by the homeowner.
If your answer to:
“When was this last maintained?”
is:
“I didn't know it needed maintenance,”
it's probably worth checking the instructions.
Don't Block Ventilation Because the Room Feels Cold
This can be tempting during winter.
A vent appears to be letting cold air in, so you cover it.
Problem solved.
Except the ventilation may exist for an important reason.
Homes need appropriate ventilation to help manage moisture and indoor air quality, and some openings or systems may form part of the property's intended ventilation strategy.
Don't automatically block:
Air bricks.
Trickle vents.
Extractor outlets.
Or other ventilation openings
without understanding what they're for.
Fixing an unwanted draught and disabling necessary ventilation are not necessarily the same thing.
Check the Door Too
An extractor fan has to move air out of the room.
That means replacement air needs to be able to enter appropriately.
In some situations, airflow through or around the doorway forms part of how the ventilation arrangement works.
If alterations have changed the room significantly—for example, different doors, flooring or ventilation components—the overall airflow may no longer behave exactly as intended.
Again, the system should be considered as a whole.
What About the “Tissue Test”?
You'll sometimes see advice suggesting holding a piece of tissue against an extractor grille to see whether the fan holds it in place.
It can indicate that some air is moving toward the fan.
What it doesn't tell you reliably is whether the system is achieving the ventilation performance it should.
A fan can move enough air to hold lightweight tissue while still performing poorly overall.
Treat it as a basic observation, not a professional airflow measurement.
Should You Just Fit a More Powerful Fan?
Not automatically.
If airflow is poor because a duct is obstructed, fitting a stronger fan doesn't necessarily address the real problem.
Likewise, duct length, routing, fan selection and the wider ventilation design can all affect performance.
Before replacing equipment, establish why the existing setup isn't doing its job.
Otherwise you risk buying a new fan and keeping the old problem.
When Is It Time to Get Someone In?
Consider professional assessment if:
The fan has stopped completely.
It makes unusual mechanical noises.
There are signs of electrical problems.
Moisture problems continue despite reasonable use.
You suspect ducting is damaged or disconnected.
You find moisture somewhere along the ventilation route.
The external outlet is inaccessible.
Or you simply can't establish whether the system is performing properly.
Electrical work in bathrooms can also be subject to specific safety and Building Regulations requirements, so this isn't an area for improvisation if work extends beyond ordinary user maintenance.
Use the Fan Properly Too
Even a good ventilation system can't help much if it isn't used appropriately.
If your fan has manual controls, use it when producing significant moisture and follow the manufacturer's guidance.
Some installations continue running after the light is switched off.
Others use humidity controls or different operating arrangements.
If you've moved into a property and don't understand what the controls do, it's worth finding out rather than assuming the fan is faulty because it behaves differently from one in your previous home.
Ventilation Problems Often Develop Gradually
That's why they're easy to miss.
The fan becomes slightly noisier.
The mirror takes slightly longer to clear.
A little mould appears in one corner.
The kitchen smell hangs around longer than it used to.
Nothing feels urgent.
But several small clues together can tell you that something has changed.
You don't need to obsess over every patch of condensation.
Just pay attention when the room stops behaving the way it normally does.
Because an extractor fan's real job isn't to make a reassuring humming sound.
It's to move air.
If the fan is running but the moisture isn't going anywhere, it's worth finding out which part of the ventilation system isn't doing its job.