How Can I Find a Suitable Fan for a DIY Air Purifier?

If you’re looking to make a DIY air purifier you will need a fan and a filter. We suggest you first find a suitable HEPA or MERV filter, then find a fan that will fit the filter. Follow these steps to find a suitable fan and motor for your DIY air purifier:

  1. Find a fan with a flat front or back. It is important to your fan has at least one flat side on it, so that when you attach the HEPA filter, it will remain flat and flush with the HEPA filter.
  2. To ensure a good fit around the HEPA filter, find a fan that is slightly smaller than the size of the HEPA filter.
  3. The size of the fan you need will depend on the size of the room you are trying to clean. For a room size of 10-202, a fan with diameter of at least 30cm is recommended.
  4. If possible, size the fan based on the airflow specifications of the fan. You can use the following as guidelines:
    • For a room of 10-20m2, try to find a fan with an airflow rating of at least 300m3/hr.
    • An approximate rule of thumb is that the CADR of an fan + HEPA filter configuration is approximately 1/5th the original fan airflow (without a HEPA filter attached)..
    • As an example, a fan with an airflow of 500m3/hr (without the HEPA filter attached) will give a CADR of approximately 100m3/hr (with the HEPA filter attached).
  5. Breathe safe!

Learn more: simple steps to building your own DIY air purifier »


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Smart Air is a social enterprise that creates simple, no-nonsense air purifier and provides free education to protect people’s health from the effects of air pollution. We are proud to be the only certified B-Corp dedicated to fighting air pollution.