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How to build your own air purifier

If you live somewhere where air quality is an issue, or if you have a common health concern like asthma, it may be time to get serious about buying an air purifier. Air purifiers — devices that clean air of pollutants like dust, smoke, mold, and bacteria — come in all different shapes, sizes, and price points. They’re ideal for dealing with unwanted smells, and they help you breathe easier. 

A good air purifier is worth its weight in gold, but if you don’t have the budget or if you need a solution in a hurry, consider building your own. A DIY air purifier takes about five minutes to put together, costs around $50, and can make a difference in a pinch.

What you’ll need

All air purifiers are fundamentally based on the same underlying model: an air filter attached to a fan. It gets more complicated from there, of course, but to build your own air purifier, all you’ll need is the fundamentals: a box fan and an HVAC furnace filter. 

  • Find a 20-inch box fan. Most box fans are the same and include three speeds. We like Lasko’s 3-Speed Box Fan because it’s so straightforward, although there are plenty of equivalent options like the Genesis 20" Box Fan or the Pelonis 20” Box Fan.

  • Get an HVAC furnace filter that’s at least MERV 13. HVAC filters are the thin, boxy filters that people use with home furnaces. They come in different sizes and with differing degrees of filtration (rated by a Minimum Efficiency Reporting Value, or MERV). We recommend getting one that’s at least MERV 13, although your needs may differ. Most furnace filters cost between $20 and $35 each, but you can save a ton by buying multi-packs like the AeroStart MERV-13 Filters 6-Pack or the FilterBuy MERV-13 Filters 4-Pack.

  • Get some tape or bungee cord. You’ll need something to attach your fan and box spring, although it won’t take much. Pick up some Scotch Tape, or if you prefer, a set of short bungee cords like the Lionma Mini Bungee Cord Set.

How to put it together

  1. Find the airflow arrows on your filter, and place the filter on the back of your fan so that air is passing through accordingly. 

  2. Secure the filter on the back of the fan using tape or bungee cord. Once you turn the fan on, the airflow will naturally hold the filter in place, securing everything so nothing falls off when you turn on the fan.

  3. Sit back, relax, and enjoy cleaner air. Place your DIY air purifier in a central location in your home, and elevate it by putting it on a table or countertop.

Monitoring results

Depending on your original air quality, you may begin to see results in as little as 12 hours. We set one up in a house affected by wildfires, and overnight our filter went from clean to dirty grey/brown.

If you don’t see such dramatic results as quickly, that’s a good thing. Replace your filter any time it becomes grey with dust and particles, and if you live in an especially large space, consider building multiple purifiers to have around your home.


Jaime Vázquez is a writer for BestReviews. BestReviews is a product review company with a singular mission: to help simplify your purchasing decisions and save you time and money. BestReviews never accepts free products from manufacturers and purchases every product it reviews with its own funds.

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