What does a pollen or cabin filter do and when to change it?

A pollen filter, also called a cabin filter, cleans the air that the ventilation system draws into your car. It catches dust, pollen and similar particles before they reach the vents, and some types also help reduce odours.

Over time it clogs. The result is weaker airflow, slow demisting, more noise from the fan and often a musty smell. How often to change it depends on the vehicle and where you drive, so check your handbook.

What is a pollen filter and where is it?

It is a pleated panel of paper or fabric, sometimes with a carbon layer, fitted in the ventilation intake. On many cars it sits behind the glovebox, under the bonnet scuttle or beneath the dashboard. The location and the ease of access vary a great deal between models.

Not every car has one, particularly some older vehicles, so the handbook is the place to confirm.

Some cars have two filters side by side, and a few have a larger one in a housing that needs a cover removed. If you are unsure, ask when you book and we will check what your car uses.

How do I know when my cabin filter needs changing?

The signs build slowly, so many drivers do not notice until the difference is obvious after a change. Common clues include:

• Weak airflow even at full fan speed
• Windows that are slow to clear
• A musty or stale smell when the fan starts
• Louder fan noise as it struggles to draw air
• More dust on the dash or sneezing for hay fever sufferers

Will a new filter help with hay fever?

A fresh filter can reduce the amount of pollen entering the car, which many sufferers find helpful in spring and summer. It will not remove every particle, and windows left open or pollen already inside the car still matter. Keeping the recirculation setting on for a while on high pollen days can also help.

A filter that has been left too long may hold on to pollen and damp, and then do the opposite of what you want.

If you drive often on country lanes with overhanging hedges, or park under trees, leaves and seeds can reach the intake and clog the filter sooner. Clearing the scuttle area under the bonnet of leaves is a simple habit that helps.

Can I change it myself?

On some cars it takes a few minutes and no tools; on others the glovebox, trim or even part of the dash must be moved. If you try it yourself, note which way the airflow arrows point, because a filter fitted the wrong way round does not work properly. Make sure you buy the right filter for your exact vehicle.

If access looks awkward, a garage can do it as part of other work or a service, which can save time and avoid broken clips.

What does a garage do and what affects the cost?

We would locate and inspect the filter, replace it with the correct type and check airflow and demisting afterwards. Cost drivers are the filter type, such as plain or carbon, and how much trim has to come out to reach it. Ask for a quote with your make, model and year.

If airflow is still weak with a clean filter, there may be a blower, flap or duct problem, and the system needs further diagnosis. A damp, mouldy smell can also mean the evaporator needs attention, and we would look at that separately.