How to make a HEPA filter system for less than $25

Many of my patients with sinus problems have underlying allergies to dust, mold, animal danders and other indoor allergens.

Since the first principle of treating allergies is to avoid the allergens as much as possible, or remove them, many doctors recommend a good high effiiciency particulate air filter.    Unfortunately, these are very expensive, running upwards of $100 dollars and as high as $300 for some models.

I recommend a very simple solution for those that don’t want to spend that much.   And I have pictured it below.  Here’s all you need to do.

Buy a 20 inch box fan, preferbly with variable (usually 3) speeds, from any hardware store–large or small.  They cost around $12-$14 .

Then buy a HEPA filter that is the same size:   20 inches by 20 inches by 1 inch thick.   You don’t need a 4 inch one.  They are too expensive.

You will want a HEPA filter that is rated at least an 8, but no higher than a 13 MERV rating.   The higher the rating, the finer the particle size that will be filtered.   But the higher the rating, then slower the airflow will be as well.   I reommend a filter between 8 and 11 or so.  That should cost about $10-11.


Simply attach the filter to the “air intake” side of the fan.  Use a large rubber band, or a couple of pieces of any sort of tape.   Duct tape works great, but it may leave a residue on the fan.







Make sure you orient the filter properly, so the arrows on the filter that demark the airflow direction are matching the air flow.

There have been some people who advocate for the commercial air filters with custom sized (expensive) HEPA filters.   One argument is that these filters have slow fans that don’t kick up dust particles.  Or that they don’t have any leaks around the filter.  Those are both true.

If blowing up dust  is a concern for you, then put this system on a timer (also inexpensive at hardware store) and have it turn on after you leave your room in the morning and turn off an hour before you come home.   That should minimize the dust that might be stirred by the airflow.  Alternatively, you can turn the fan to low.

You can tell when its time to change the filter by the color of the filter.    In the second photo you can see a new filter that is pur white, with an older filter, yellow from all the debris caught in the filter.  Definitely change the fil

ter before it gets this dirty. DSC_0011.JPG

Thats it.


If you are looking for a really expensive air filtration and purification system, with all the bells and whistles, I will write about that later (assuming I hear from a couple of readers).

I hope you find this useful.


Jeffrey E. Terrell, MD

Michigan Sinus Center

Follow Sinus411  on Facebook, too, by CLICKING HERE






2 comments to How to make a HEPA filter system for less than $25

  • Brandy

    Oh my God!!! My child has severe asthma and allergies!!! We use box fans yr round. Wish I’d herd this before now. I’m gonna but 2 filters tomorow and see what happens! Thank you soooo much for posting this info! I’ll let you know what happens!

  • This is a really great idea. I love my big air cleaner because it also blocks street noises while I sleep. But regular fans attract a lot of dust, and they tend to be made now so that you can’t take them apart and clean them. So your very practical suggestion solves two problems at once. Thank you!

    (P.S. When my first air cleaner broke, I needed an interim solution. So I removed the donut-shaped HEPA filter, set it on the floor, and laid a box fan on top. Not very elegant, but it worked. :)

Leave a Reply

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>




A sample text widget

Etiam pulvinar consectetur dolor sed malesuada. Ut convallis euismod dolor nec pretium. Nunc ut tristique massa.

Nam sodales mi vitae dolor ullamcorper et vulputate enim accumsan. Morbi orci magna, tincidunt vitae molestie nec, molestie at mi. Nulla nulla lorem, suscipit in posuere in, interdum non magna.