The best portable home air purifiers can be sinfully expensive. I know of a True HEPA air purifier with medical-grade air filters that lives somewhere north of $1,000. But dropping a grand on an air purifier is insanely expensive for most people.
Related: How to Clean a HEPA Filter
But there’s good news, too. You can actually build your own air purifier at home using relatively inexpensive supplies. I’m about to show you how to DIY your own air cleaner — how to make a simple air purifier at home.
Can I Actually Make My Own Air Purifier At Home?
Yes, you ABSOLUTELY can. And you don’t need any kind of expensive equipment, materials, or technical know-how to create a simple but highly effective DIY home air purifier. With a MERV-rated furnace filter measuring 20″ x 20″x 1″ or a HEPA filter and a 20″ x 20″ box fan, you can make a home air filtration system in 30 minutes tops.
How to Make an Air Purifier Using a Box Fan and a Merv-rated Furnace Filter
First, gather the following supplies:
- Clear packing tape: I recommend the Duck HD Heavy Duty Clear Packing Tape. It costs roughly $15. Since the tape is over 50 yards long, you’ll use it for many future builds.
- A MERV-rated furnace filter or a HEPA filter: A MERV 10-12 filter should be fine. Usually, the filter manufacturer indicates the rating of the filter somewhere. But not everyone uses the MERV filter rating. If it’s a different rating, choosing one with a higher rating is best. Expect to spend between $17-$20.
- *A traditional air filter/furnace filter with a MERV rating of 12-13 performs at a level that’s not too far away from HEPA filtration. If you’re looking to remove really small particles, go for a HEPA filter.
- A flat, square-shaped box fan: I recommend the Holmes Box Fan. It retails at around $18-$20. Why a flat box fan? Because you’ll be working with a flat furnace filter/HEPA filter, which means you’ll have a better seal (no leaks). An awkwardly shaped fan would make achieving a tightly seal incredibly harder if not impossible.
Follow this make-an-air-purifier-at-home-guide, and you’ll end up with a device that cleans the air pretty much like any other mechanical air cleaner out there.
Step #1: Find a comfortable working space. A table will do.
Step #3: Disconnect the box fan from power (if using an existing fan) and stand it on the table.
Step #4: Take the furnace filter/HEPA filter and place it on the front or back of the fan. I prefer to put it on the front.
If you put the filter on the front, adjust the fan speed knob to the highest setting (usually 3). Then, take off the grating on the front using pliers. Next, remove the knob because if you don’t, the filter won’t be able to lie completely flat on the face of the box fan.
Some people feel the filter should be on the front of the box fan while others feel it should be on the back. But does it matter what comes first, the filter or fan?
Someone here carried out tests in an attempt to settle this debate. And the test results showed it doesn’t matter whether the filter goes on the front or on the back of the box fan.
Step #5: Align the two so that they stand side by side and tape them together.
- Since the box fan and filter are the same shape and size, aligning them should be easy. What if the fan and HEPA filter aren’t the same size with the filter being larger? In this case, use a string to hold the two firmly together as shown in the image below.
- Holding the fan and the filter together with one, put some clear packing tape on one side of the filter’s edge. Then, tape the remaining edge of the tape against the frame of the box fan.
- Firm the tape down onto the “join” and all around it. Once done, repeat this step for the remaining three sides.
- Make sure that the taping you did creates a tight seal between the edges of the fan and those of the furnace filter/HEPA filter.
- Inspect your unit for gaps. And if you spot any gaps on the frame, use extra tape to cover them. If you don’t do this, some of the air won’t get into the filter, something you don’t want. You may not get an airtight seal the first time round, but once you get the hang of it, you’ll do it right each time.
- Plug in the homemade box fan air purifier and voila! air purification kicks off.
Watch the video below to see someone building an air cleaner using a box fan and a furnace air filter.
Use the Right MERV Air Filter for the Build (10-12 MERV)
Get one of those white felt MERV-rated air filters or a True HEPA filter. Traditional air filters cost $20ish. And their tightly woven felt-like structure captures tiny particulates really well. But they’re not as thorough as True HEPA filters as far as air purification.
True HEPA filters can be pretty expensive. Some cost way more than what some decent air cleaners do! You can get a good one at $30-50 though.
Stay away from those cheap blue or green MERV air filters. They may be cheaper, but that’s because they’re pretty basic filters that don’t do much of anything.
These cheap blue and green air filters seem like they’re constructed using loosely woven nylon strings. They look like a net of sorts, and while they may trap the largest air contaminants, they let the finest air contaminants in the room pass right through. And it’s the smallest air particles that keep folks with breathing issues awake at night.
BTW, what rating should you aim at when choosing the right furnace fan for the build? Get a fan with a MERV rating of 10-12. That’s what works best for this sort of setup.
How Well Does a Box Fan Air Purifier Clean Indoor Air?
I no longer use a homemade air purifier, but when I completed this little project a few years ago, I got decent results. It certainly made a difference in the air quality of the room.
An indoor air quality expert I bumped into on YT when researching for this post actually measured the air filtration efficiency of a Box fan air purifier at clearing up smoke particles. The tester burned a couple of matches in a room and fired up their made-at-home air purifying device and left it to purify the air for 30 minutes.
And the findings were interesting:
The box fan air cleaner removed fully 87 percent of the particles compared to a performance of 99 percent from a HEPA air purifier, the Coway APH-115. These results are pretty similar to what a few other testers got.
Conclusion: A properly built homemade air cleaner gets the job done, but it’s not as efficient at filtration as a good residential home air cleaner.
Also, this simple purifier isn’t a permanent air-cleaning strategy because its longevity is questionable. In the end, you may need to invest in a decent home air cleaner such as these Medify air purifiers or these Levoit purifiers or these Airthereal air cleaners.
Does a Homemade Air Purifier Make Sense?
Total budget needed to build a simple air cleaning system at home: $50-$55. Here’s the kicker. Amazon and many other places online offer tons of complete HEPA-filter air purifiers at $50ish.
But that’s not all.
The simple mechanical air cleaner we’re about to build doesn’t filter mold, dust, bacteria, and virus-laden indoor air as efficiently as do factory-made HEPA air purifiers.
If you’re looking for a fun Saturday afternoon project to complete and aren’t too concerned about aspects such as performance versus the spend, go ahead.
But if you want a homemade air purifier that costs very little to build, filters out impurities incredibly well a long-term air cleaning solution, this isn’t the idea.
If you’re interested, here’s a list of good filter-based air purifiers that cost under $50.
2. JINPUS Small Bedroom Air Cleaner
3. POMORON MJ002H 4-in-1 Home Air Purifier
4. KOIOS Small-space Air Purifier
5. RIGOGLIOSO Compact Bedroom Air Purifier
All of these little air cleaners cost less than $50 at this writing. Click each link to see the current price at Amazon. They work best for small rooms because all of them have a really small CFM. BUT they work.
What if I have all these materials lying around? In that case, building an air purifier at home will cost you absolutely nothing!
Final Thoughts on Homemade Air Cleaners
There you have it! That’s how you construct a simple air cleaner at home using readily available and cheap materials. It’s doubtful this is the only room purifier you’ll ever need though. It’s a short-term contaminant removal strategy.
But if wildfire smoke’s blowing into your home right now and you can’t get your hands on a dedicated HEPA air purifier, go head and build your own air purifier and deal with the emergency.