How To Make A DIY Air Purifier In 5 Easy Steps!

Josh Mitchell

Written By

Josh Mitchell

Expert Reviewed By

Holly Curell

Last Updated On

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Key Takeaways

  • You can easily make a DIY air purifier using accessible tools and materials that you can easily find in the market.
  • As far as effectiveness goes, DIY air purifiers can at best remove 90% of small particles. 
  • Depending upon your budget, you can choose to make a DIY air purifier either using MERV or HEPA filters. 

I’ve noticed a surge in the number of individuals interested in DIY projects in recent years, and this trend has finally spilled over into the air purifier market.

Air purity plays a vital role in our health, so I am all for people getting an air purifier using any means available.

If you’re a fan of DIY projects or if an air purifier just isn’t in the budget right now, we’ve got you covered.

Below I’ll explain the 5 easy steps on how to make your very own DIY air cleaner. Keep reading below to find out more!

5 Steps To Make An Awesome Homemade Air Purifier

I get it – air purifiers can be expensive. Fortunately, the 5 steps below make air purifiers accessible to everyone. My list of tools and materials is short because I want DIY air filtration units to be accessible to everyone. All you’ll need is a box fan, string or bungee cord, an air filter, pliers, and measuring tape – things that can be found at all hardware stores.

if this sounds too good to be true, studies have shown that even DIY air cleaners can dramatically decrease the amount of black carbon and smoke pollution in the air. These homemade “filter fans” can remove up to 90% of small particles.[1]

Without any further delay, let’s build some DIY units!

1. Buy Any Box Fan

First, you need to get your box fan which will be the core of your air cleaner. The sizes vary, but a fan measuring 20 x 20 inches will work best for what we’re trying to accomplish. You don’t have to spend a lot of money on a box fan, and I find them in thrift stores all the time (just be sure you’re not buying a damaged or malfunctioning fan).

Make sure your box fan has a flat front and back so you can easily strap your filter on later. Box fans with a flat front will have a recessed motor, so be on the lookout for that feature. Follow the box fan manufacturer’s instructions when setting it up.

2. Buy A Filter That Is Similar In Size

Once you’ve purchased your fan, you can get your filter for your DIY air cleaner. Just be sure the filter is the same size or larger than your fan and pay attention to what it can filter.

I always use HEPA air filters for these projects (more on that later), but you may opt for a MERV filter if you’d like. Whatever you choose, make sure it overlaps your box fan and can effectively protect your home against wildfire smoke, harmful particles, and allergens.

3. Remove The Grating From The Fan (Where Possible)

Now the real work starts. Depending on where your fan controls are, you may need to remove the grating from the front of the fan. This will also increase the amount of fan airflow leading into the filter.

The fan knob, in particular, can get in the way of a HEPA filter. Therefore, use your pliers to pull off the knob and grating, so you have a perfectly flat front surface.

I need to point out that this step may void the warranty of your fan. You’ll also no longer be able to control the speed of your fan since the knob has been removed. You’ll need to set your fan speed to the max before pulling off the knob.

This step isn’t mandatory, but it will provide the best mounting experience for your DIY air filter.

4. Attach The New HEPA Filter

With your string or bungee cord, attach the HEPA filter to the front of your box fan. You could probably use tape or rope, but high-quality string fastened in a tight knot is optimal.

There are various sources online that state you should attach your air filter box to the back of your fan. While this isn’t necessarily wrong, studies and data have shown better results with a front-facing filter.[2]

5. Enjoy Cleaner Home Air

You can now sit back and enjoy cleaner air via your new DIY air cleaner. Remember to place it in the room that you are in the most! Just like regular purifiers, you’ll need to replace the air filter in your DIY purifier. Keep an eye on it to ensure it doesn’t get clogged with dust and other contaminants.

MERV Filters Vs HEPA Filters: Which Is Best To Use?

MERV, also known as “Minimum Efficiency Reporting Value,” is a system used to measure a filter’s ability to capture particles of a certain size range. The MERV rating scale ranges from 1 to 20, with higher ratings indicating better filtration performance. While MERV filters can capture particles as small as 0.3 microns, they can also capture larger particles.

Filters with MERV ratings of 17-20 are rare in residential and commercial settings. They are typically used in specialized applications such as clean rooms or laboratories.

Filters with a MERV rating of 12 to 16 can be used in residential homes and remove up to 75% of airborne contaminants depending on the specific particles in the air and the airflow rate through the filter.

HEPA or High-Efficiency Particulate Air filters are designed to immediately trap particles and capture all viruses and contaminants. HEPA filters are rated using their own standard, known as the HEPA standard.

All HEPA air filters must meet a minimum efficiency of 99.97%, making them ideal for places such as hospitals. A DIY HEPA filter may have higher efficiency, but they are often more expensive when compared to MERV filters depending on the size, type, and brand. A worthwhile expense to capture more particles.

However, if your home is prone to pollution or you want to filter smoke, it’s worth investing in a high-quality HEPA filter for your air cleaner.

How Effective Is Your DIY Air Purifier Against Common Problems


Common airborne allergens include pollen, spores, pet dander, dust mites, and mold. A MERV filter with a rating of 16 or higher can capture at least 95% of airborne allergens 0.3 microns or larger. However, allergens like certain types of viruses, bacteria, and gases, may be smaller than 0.3 microns and may not be captured by a filter with a MERV rating of 16 or higher.

DIY air filtration units with a HEPA filter can capture 99.97% of airborne particles 0.3 microns or larger. This makes it more effective than filters with a MERV rating of 16 or higher for capturing allergens.


Dust can be as small as 0.1 microns, but most will likely be larger than 0.3 microns in size. This gives your DIY air cleaner an even greater chance of trapping particles.

A MERV rating of 12 and above can trap up to 90% of particles that are 3 to 10 microns in size depending on air flow rate and filter thickness.

Viruses / Covid

No definitive research proves the effectiveness of air purifiers against COVID-19. However, air cleaners with HEPA filters may help reduce the concentration of small airborne particles, including those containing the virus.

Some experts believe that although COVID-19 particles are small, they may be carried by larger particles more easily captured by HEPA air filters.

So while we can’t be sure what percentage of COVID-19 particles can be caught by an air purifier with a HEPA filter, they may provide some benefit in reducing the concentration of small airborne particles in general, potentially including particles carrying the virus.

Pet Hairs And Odors

HEPA filters are very effective at capturing and eliminating pet dander because it’s typically larger than 0.3 microns. A HEPA filter can capture up to 99.97% of particles that are 0.3 microns or larger, including pet dander.

However, HEPA air filters may be less effective when it comes to odors. While HEPA filters can capture larger odor particles like those from pet hair and dander, they are not explicitly designed to remove odors from indoor air.

What Is A Corsi-Rosenthal Box?

A Corsi-Rosenthal box is a DIY air purifier that was designed during the COVID-19 pandemic to reduce the levels of viral particles indoors.

Unlike a traditional box fan filter design, the Corsi-Rosenthal was originally made to house 5 filters (preferably MERV 13 and higher) on the sides and bottom of the cube.

A 20-inch fan would then be mounted with duct tape on the top of the cube to draw indoor air through the filters and up/out of the box. The overall cost fluctuates from around $50 to $150.

Important Tips While Using A Fan

  • The filter fan should be positioned in the middle of the room, away from walls and drapes.
  • You may need multiple filters/air purifiers or portable air cleaners if your house is particularly large.
  • MERV filters should have a rating of 13 or higher to effectively filter out smaller particles
  • HEPA filters should be replaced every 6 months, while MERV filters should be replaced every 90 days. Follow the manufacturer’s instructions or replace the filters when they become visibly dirty or clogged.
  • Close all windows/doors for best results when running air cleaners. However, always ensure proper ventilation, especially if multiple people are occupying the space.

Frequently Asked DIY Air Purifier Questions

How Much Does It Cost To Make Your Own DIY Air Purifier?

The total cost should be approximately $25 to $50 to make your own DIY air purifier. The ultimate price is determined by the type of filter and the quality of the fan. For example, thicker filters will cost more.

How Long Does It Take To Make You A DIY Air Purifier?

You can make your own DIY air purifier in just 5 minutes if you’re handy! If you’re still unsure, search YouTube, and you’ll find multiple videos to watch that go through all the details/steps.

Are There Any Risks When Making Your DIY Air Filter?

There are potential risks when making your DIY air filter, but they’re the same risks you assume when using any air filter. Be sure to use a high-quality filter and your fan should be new or just a few years old to avoid any potential fire hazards.

What’s The Clean Air Delivery Rate Of A DIY Air Purifier?

The CADR (Clean Air Delivery Rate) of a DIY air purifier will depend on the size of the device, the quality of the filter, and the fan’s airflow rate. Typically, CADR ratings are only given to commercially manufactured air purifiers that have undergone standardized testing.


I love seeing people take control of their indoor air quality. Even if you can’t afford a brand-new air purifier, you can have your very own DIY air cleaner after a quick trip to the store and about 5 minutes of work.

With a 20×20″ box fan, a high-quality filter, string, and a few workshop tools, I’m confident you can make your own air filter that will work for you!

Enjoy your clean air!


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Josh Mitchell


Josh Mitchell
My name is Josh and I am obsessed with home appliances. From portable AC units to heaters and air purifiers, I enjoy testing, learning and using these devices to improve the air quality inside my family home.

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Midea U Shaped Window Air Conditioner

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