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The Ultimate Guide to Vacuum Cleaner Filters

Written by James Hall |

Are you thinking of buying a new vacuum cleaner but are confused about filters? Or do you have an allergy and want to know which is the best filter? This article explains everything you need to know about vacuum filters.

An overview of vacuum filtersBottom Line

  • Vacuum cleaners need filters to prevent dust and other allergens escaping back into the air.
  • Many vacuums have a primary and secondary filter. For bagless vacuums, the primary is often the cyclonic system. For bagged, it is the bag itself.
  • There are a variety of types of filters, including sponge, disk, cloth and cartridge.
  • Basic filters use a “sieve” method to remove particles, but smaller allergens can pass straight through.
  • HEPA filters are more effective, as they use a variety of methods to trap smaller particles.

Why Vacuums Need Filters

At their most basic level, vacuum cleaners suck up particles before depositing them into the canister. As the vacuum can’t continuously fill up with air, it also needs to expel “exhaust” air back into the room.

Without a filter, the exhaust air would be filled with dust and other particles. This would cause increased allergy symptoms, a musty smell and spread bacteria around the home. It would also mean vacuuming was just moving dirt around the house!

To avoid this, all vacuums come with filters. The purpose of these filters is to remove dust and dirt before it escapes back into the room. Where vacuums vary is the effectiveness of the filters they use.

Primary & Secondary Filters

The first thing to note is that many vacuum cleaners come with more than one filter.

  • Primary filter. The primary filter collects most of the dust, dirt and other debris in the vacuum’s canister. In the case of a bagged vacuum, the bag itself usually acts as the primary filter. Air can pass through small holes in the bag, while dust and dirt remains inside. Bagless vacuums may have a pre-filter before the dirt canister, but the canister itself can act as a filter. In the case of a cyclonic vacuum, for example, the circular motion causes heavier particles to be pushed outwards and caught.
  • Secondary filter. Many vacuums also come with a secondary filter. For bagged vacuums, the secondary filter is placed after the bag to remove smaller particles. Bagless vacuums often have a filter after the collection canister.

Not all vacuums have multiple filters though. Some bagged vacuums rely on the bag alone, while cheaper bagless models tend to only have a single filter after the dust canister.

Keep in mind that the design of the vacuum can also play an important role in the level of filtration. A vacuum can still release plenty of allergens even if it has a great filter, for example, if some of the air is able to leak around the filter.

Types of Filters

While all vacuum filters have the same purpose, they come in a variety of shapes and sizes. Some of the most common include:


Vacuum bags act as initial filtersBagged upright or cylinder vacuums use the bag as the primary filtration system.

Bags are made from synthetic material, cloth or paper. As air enters the bag, it is able to escape through small holes. Any dust and dirt that’s larger than the holes is caught and deposited into the bag.

As you can probably tell, smaller particles are able to escape. This is why the best bagged vacuum cleaners have a secondary filter.

Cyclonic Action

Many bagless vacuum cleaners, including the Dyson range, use cyclonic action as their first filter.

Instead of a physical filter, air is spun around a cyclone in the middle of the canister. Dirt particles are forced outwards, in the same way that you feel an outward force while riding a carousel.

As dust is forced out, it leaves the air and falls down to be collected in the canister. Air is instead forced upwards, where it is often then passed through a secondary filter.

Foam Filters

An example of a foam vacuum filterFoam filters are probably the most basic type. Air is forced through a layer of foam, which collects small dust particles and allergens.

Foam filters are usually placed after the canister or primary filter, as they are not designed to handle larger debris. They are often washable, but you should check with the manufacturer first.

The downside to this filter is that it can quickly become clogged, so it needs regular cleaning. If you have a Shark vacuum, we’ve written a detailed guide to cleaning a Shark’s foam filters.

Disk Filters

Disk filters are often made with paper or types of cloth. The disk shape allows them to fit into smaller devices, but they typically need to be cleaned more often than other types of primary filter.

Cartridge Filters

An example of a cartridge filterOne of the most common types of vacuum filters are cartridges. They are circular in design and often made with folded paper or synthetic materials. This increases the surface area and allows for greater filtration.

While some cartridge filters are washable, others need to be replaced when dust can’t be removed with via tapping.

Cloth Filters

Cloth filters are the most robust, so are typically found in industrial vacuums. They are designed to filter large or potentially heavy debris without being damaged, which means they are best suited to workshops or on-site locations. They can also be washed and reused.

The downside to cloth filters is that they aren’t great at removing smaller particles. This is why they are often used in conjunction with secondary filters.

Filtration Methods

Aside from the type of filter, the method of filtration can also vary.


A basic filter works by forcing air through a fine mesh in a similar way to a sieve. Air can pass through the small holes, while dust and dirt that’s larger than the holes is caught. There is a limit to how small the holes can be without reducing suction power though.

As you’ve probably guessed, this type of filter isn’t effective at removing the smallest particles of dust and other allergens. It’s a simple way of removing most particles from the air though.


A HEPA vacuum filter is designed to fix the shortcomings of a standard filter. It was originally developed to remove radioactive particles from lab environments, but the technology has proven effective for use in home appliances.

Unlike standard filters, HEPA filters use several methods for removing particles. They also don’t rely on basic filtration. This allows them to remove up to 99.97% of particles with a diameter of 0.3 microns or more.

If you suffer from allergies, we recommend looking for a vacuum cleaner with a HEPA filter. Just make sure the vacuum has a HEPA filter that matches the 99.97% standards, as some brands have started to sell “HEPA-style” vacuums that aren’t as effective.

A downside to HEPA filters is that they can restrict airflow. This means a vacuum cleaner must output more power to generate the same level of suction.

Side note: ULPA filters are a step up from HEPA. They can filter 99.999% of particles down to a size of just 0.12 microns, making them suitable for commercial usage. ULPA filters aren’t as robust as HEPA, however, so they typically aren’t found on consumer models.


Some SEBO vacuums come with S-Class filtration systems. These aren’t as effective as HEPA, but can still filter up to 99.9% of particles at 0.3 microns or smaller.

Activated Charcoal

Charcoal filters are designed to eliminate odours, which is why they are commonly found in pet vacuums.

Activated charcoal is carbon that’s had oxygen added to it. This allows air to pass through, but attracts certain substances (while ignoring others). The result is that some odours are absorbed and the air comes out smelling fresher and cleaner.

An activated charcoal filter has a limited number of “bonding” sites. Once these have been taken, the filter won’t work and needs to be replaced.


The wide range of vacuum cleaner filters can make it difficult to know which is the right choice. Manufacturers don’t help by overselling the efficiency of their vacuum’s filters or claiming to have “HEPA-like” filters. Hopefully the information in this article will help you make an informed decision about the best filter for your needs.

If you have any questions about vacuum filters, or anything related to vacuums, let us know in the comments! You may also want to read our article about how often you should clean a vacuum filter.

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