Expert advice on pollen filters

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You've probably heard people mention pollen filters. But what are they? Where are they, and do they need replacing?

What is a pollen filter?

You may, understandably, think that a pollen filter is there to filter pollen. And you'd be right. But they do more than that. Pollen filters could be more accurately described as cabin air filters as they actually filter out debris, spores, pollution, and some even prevent odours from entering the cabin.

They can extend the life of the car's heating and ventilation system, and lower the amount of pollutants and allergens from entering your car - which is great news if you're a hay-fever sufferer, or an asthmatic. They were originally fitted to cars to protect the air conditioning system, but now most new cars come with them as standard.

What are they made of?

They generally come in two types, an electrostatic paper element, or a carbon impregnated filter. The paper elements are by far the most common, and air coming into the cabin first flows through the filter element, and here most of the contaminants get trapped. Carbon filters perform the same function but the carbon also works to neutralise and absorb unpleasant odours.

How often should I replace it?

Most manufacturers have service intervals of between 12-20K miles, or 1-2 years depending on the type. It's not a safety critical component, so not replacing it won't cause any issues with the car mechanically – but you may find that the interior becomes smelly, particularly when you use the air conditioning. Replacing the filter, and using a decent air-con system cleaner can often solve this.

You may be surprised at how much gets trapped by the filter, especially if you do a lot of town driving. If you're unsure whether it needs replacing, and when it was last replaced it's worth finding where yours is, popping it out and giving it a visual inspection. Unless it's clean and 'fresh' looking, swap it for a new one.

Where is the pollen filter?

It varies from car to car but you'll always find them somewhere between the engine and the driver! Often they're behind, or underneath the glovebox, or behind a trim panel in the lower dashboard. In some cars they're in the scuttle area beneath the windscreen. If in doubt consult your handbook or check the internet. It's not common to find one that's difficult to access, so they're generally fine even for amateur DIYers to attempt.

How do i replace it?

Once you've located the filter, it's simply a case of removing the old one and slotting in the new one. It makes sense to vacuum around the area to make sure you remove any dirt or dust that's hanging about. If the filter is beneath the windscreen it's vital that you replace any cover so that the seal is watertight.

If your filter gets wet it will quickly become mouldy and the car will smell damp. If this happens remove the filter, find out where the leak is, and replace with a fresh one. A leaking pollen filter can cause water to enter into the cabin, which is obviously the last thing you want to happen! So take your time, and make sure any seal, or cover is in good order before you replace it.

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