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How do I compare two room air purifiers?

It is possible to compare two room air purifiers by looking at their Clean Air Delivery Rates (CADR) The higher the clean air delivery rate, the faster the purifier will clean the air. Another useful measure is the effective room size. Ensure the air purifier you purchase has an adequate effective room size.

Further information concerning CADR and details of how to measure the size of a room are detailed below.

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What is Clean Air Delivery Rate (CADR)?

Clean Air Delivery Rate (CADR) is a measure of an air cleaner’s delivery of particle-free air. It is calculated from independent laboratory tests. To compare two room air purifiers look at the CADR numbers. CADR is measured across 3 particles; Smoke, Dust and Pollen, which due to their different sizes are filtered at different rates. The combined CADR is the rate for each of the particles added together to provide an accurate picture of the overall effectiveness of the purifier. The higher the CADR, the quicker the air cleaning. It is measured in cubic feet of particle-free air per minute. Because CADR is independently tested it is the most reliable way of comparing two room air purifiers.

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What is the benefit of using replaceable filters?

Once a filter has become ‘fully loaded’ with particles it will become much less effective at filtering due to reduced air flow and lost electrostatic charge. Some permanent filters require regular cleaning or washing. This process often returns particles back to the environment and doesn’t effectively remove all the particles from the filter. Cleaning and washing a filter may also remove its electrostatic charge and as a result impact the filters ability to capture particles. By replacing a filter after 3 months of continuous use effective purification is delivered on a sustained basis. Once Filtrete filters are fully loaded they and the captured allergens can then be disposed of effectively and easily.

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How do I work out the size of a room?

The size of a room can be calculated by multiplying the width of the room by the length. For example if the room is 3m wide and 4m wide. The room size is 12m2.

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How much does it cost to run a Filtrete room air purifier?

Filtrete room air purifiers are very cost effective to run. See the below table for cost details. All costs based on £0.108 per KWH with the purifier on high speed setting running constantly.

  FAP02 Ultra Clean
(Small size)
FAP03 Ultra Clean
(Large size)
Cost per hour £0.0059 £0.019

*HEPA purifiers with comparable room size and CADR.

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How noisy are the Filtrete room air purifiers?

Decibels are a subjective measure of noise level. The higher the number, the louder it is. To give an example of noise level – a typical fridge may be around 50 decibels. A change in 2 decibels is generally noticeable to the human ear.

Model Description Decibels Low Decibels Medium Decibels High


Filtrete Ultra Quiet Air Purifier





Filtrete Ultra Clean Small Air Purifier





Filtrete Ultra Clean Large Air Purifier




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What size are the air purifiers?

Product Height Depth Width





FAP02 Ultra Clean Small




FAP03 Ultra Clean Large




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Are Filtrete Air Purifiers covered by a warranty?

Filtrete Air purifiers are covered by a two year warranty, valid only with a copy of the original receipt or invoice received when purchased. If your air purifier develops a fault within two years of purchase please contact our customer helpline on 0845 603 5575 or alternatively use the contact us webform on the left hand side of this page.

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Who can I contact if I have further questions?

If you still have an unanswered question, please contact the 3M Filtrete Air Purifier customer helpline on 0845 603 5575 or alternatively use the contact us webform on the left hand side of this page.

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Allergy Info Centre

 Allergy Info Centre

Find out which airborne particles and allergens can trigger Hay fever and asthma attacks.