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Vacuum Cleaner Filter FAQ

Q&A About Vacuum Cleaner Filters

by Ed Gadziemski

What are important filter characteristics?

Filter efficiency is determined by the type, size, and the number of particles the filter is able to trap. Overall filter performance depends on a number of factors:
  • Is it pleated? A pleated filter provides additional surface area on which particles can be trapped
  • Is it electrostatically charged? Filters with electrostatic charging can attract and capture particles that other filters can miss
  • What is the filter substate's efficiency? HEPA filters, for example, can capture up to 99.97% of dust and dirt particles
  • What type of particulates does it capture? Some filters will clog when faced with fine particulates like drywall dust. Others capture tiny particles like pollen and soot

How many filters does a vacuum cleaner have?

Not counting the bag, which is part of the overall filtration process on bagged vacuum cleaners, most vacuum cleaners possess at least two filters. They are:
  • (Bagless only) Dust cup filter - traps dirt inside the dust container
  • Pre-filter (also known as pre-motor filter, motor filter or after bag filter) - filters air before it enters the suction motor
  • Exhaust filter (also known as final filter, output filter or after filter) - filters air returning to the room

How effective are multi-layer filters?

  Experiments were conducted on the filtration performance of multi-layered media, such as the white-yellow-green filters used by some vacuum cleaner manufacturers. The experiments showed that multiple layers do not perform as well as calculated from filtration data on the individual layers. The layers must be separated for best results.

What is HEPA Filtration?

HEPA (High Efficiency Particulate Air) is a filtering efficiency specification for highly sophisticated filters developed during World War II to remove radioactive dust from nuclear power plant exhausts. HEPA filters must retain all particles as small as 0.3 micrometer (formerly microns) with an efficiency rating of 99.97%. A 0.3 micrometer filter will capture soot, pollen, black and color copier toner and the majority of atmospheric dust particles.

HEPA filters are a pleated or 'extended surface' filter made of glass microfibers. The HEPA acronym is used primarily in the United States, while Europeans often refer to the same filter as an S-Class filter. Certified HEPA filters in both the U.S. and Europe are marked with a certification number. The United States Department of Energy (DOE) has specific requirements for HEPA filters in DOE regulated applications.

What is a sealed HEPA system?

A sealed HEPA system is not only a HEPA filter but an entire system that meets HEPA standards. This is accomplished by preventing air passing through the system from escaping around or under the filter. If you have a HEPA filter but air escapes without passing through it, the filter will not accomplish its intended purpose. Sealed HEPA systems avoid this by using special filter mountings and other techniques.

Is HEPA always HEPA?

Some manufacturers have developed their own terms. For example, several manufacturers use a 'HEPA type' filter which does not meet the stringent standards set for a true HEPA filter. The key to proper comparison is the size and percentage of particles captured. Almost any system could be rated at 100% filtration if the dirt particles are large enough, so make sure to evaluate not only the percentage but also what size particles are filtered at that percentage.

What about allergens?

  Dust mites (pictured at left) cause allergic responses in many people. It is not the mites themselves that are the problem, it is their waste products. Mites shed their skin and the cast-off skin becomes part of the dust load in your home. In addition, their feces join the cast-off skin and other particulate matter that makes up household dust.

Does this mean special filtration and super efficient vacuum cleaners are required? No, most standard vacuums and all HEPA vacuums will easily handle dust mite detritus. However, for those with significant allergic reaction to multiple substances, HEPA filtration becomes more important, as it will remove not only dust mite leavings, but other even smaller allergens your home contains.

How often should I change the filters on my vacuum?

In general, plan to change foam, cloth or paper pre-filters and exhaust filters every three months. Change them more often if your home is large or has new carpet, if you have children, if there is a lot of foot traffic in your house or if you have pets.

HEPA filters need to be changed (or cleaned, if washable) every six to twelve months. If you cannot see light through the filter when holding it near a light source, change it immediately.

Filters are either disposable, washable or vacuumable. You should follow the manufacturers' guidelines on how often to change, wash or vacuum the filter in your particular vacuum cleaner. Note that cleaning a washable filter requires you to handle the dirty filter - exposing you to dirt and any captured allergens. A disposable filter results in much less exposure since you just place it in the trash.

Tip: When you change your filter, mark the date on a calendar or write it on the filter itself so you know how long it has been since it was replaced.

What happens if I do not change my vacuum cleaner filters?

Vacuums lose suction power and eventually stop picking up dirt when the filters are dirty. Some poorly designed motor filters let air bypass the filter when they are dirty. This can damage the vacuum cleaner's suction motor and result in an expensive repair.

In addition, a clogged output filter (alternatively known as exhaust filter or after filter or final filter) increases strain on the suction motor. This can result in poor suction performance and reduced motor lifespan. In some cases, it can even cause the vacuum cleaner's plastic case and filter mountings to melt and warp. If this happens, you may not be able to ever replace the filter again because a new filter will not fit into the warped plastic.

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