CleanAirKits - Corsi-Rosenthal Box

An extremely effective option is a Corsi Rosenthal box, they're diy and dirt cheap, but kind of ugly. Just Google Corsi Rosenthal box and there are directions everywhere, or you can buy an assembly kit on Etsy for pretty cheap

I still love my Corsi Rosenthal air purifier.  Its on an Alexa plug and turns on at night in my living room. 

If i wanted to upgrade from my CorsiRosenthal, this is where I'd start. https://www.cleanairkits.com/

Coris rosenthal or the Coway filters. Don't just run them now, run them all the time. Great way to remove dust, allergens, and viruses from the air.

I've bought a couple of Luggable air filters from [Clean Air Kits](https://www.cleanairkits.com/) that seem to work really well. They're tall but skinny. They're built with computer cooling fans, so they move huge amounts of air very quietly. And they use the same Filtrete MPR1900 filters that you would use in a furnace/central air system.

A CR box made with computer fans (like [this kit](https://www.cleanairkits.com/)). The nice thing is that the filters are generic MERV 13 filters, which are fairly widely available.

A [CR box](https://corsirosenthalfoundation.org/instructions/) (Filtrate 1900 or MERV 13 furnace filters and a box fan) is your best option: they're cheaper and more efficient than commercial air filters; because the filters are just furnace filters, you can get them basically anywhere; and they can be designed in lots of ways to suit your space (the standard 4-filter design, two filters in a triangle shape with the fan as the third side, one filter with a spacer between the fan and filter, two or four filters with computer fans for quieter filtration, mounted to a wall like a floating shelf, etc). Look online for pictures and further instructions for different shapes.

The only viable option for affordability short term and long term.

r/crboxes Cheapest and best option available both up front and over time https://www.cleanairkits.com/ just an example of a pre-made kit, I'd recommend making something with a 4-5" thick filtration medium for longevity over buying a 1" filter kit. Those 4" filters last a year for $90 The total cost of a project like this should run you about $200-300 depending on what fans and materials you use

The best is a Corsi Rosenthal box. You can make your own but people have started to make fancy enclosures and you'd just need to change out the HVAC filters as needed. They're the best performing and quieter than commercial units with their proprietary filters. https://www.cleanairkits.com/ is an example.

I'm here to pile on to the "Corsi Cube" brigade - they are the cheapest and work the best!

I am currently running the house special of "I bought whatever was on sale at the time." So I have a mix of Levoit, Winix, Blueair, and a couple of decades old Honeywells to round it out. My AC system also has a "circulate" option and has a built-in HEPA filter and UV light. I monitor it all with a Airthings 2960 (one upstairs, one downstairs). Currently, I am trying to consolidate to a single brand (settled on Levoit - 300 and 600 sizes) just to make filter replacement simpler. Trying to get to a 6mo filter replacement schedule (currently closer to 4mo here in Texas, thanks to all the allergens). From my testing, here's the short version - as long as it moves air and has some sort of filtration, it'll probably help the air quality in your home. Everything else - air quality monitoring, app access, noise level - it's all bonus features that don't really affect the overall performance of the device. According to my Airthings AQ monitor, they do make a difference. I see VoCs and PM1 and PM2.5 go down when you ramp up the filter fan speeds. For recommendations - Level 1 - regularly change the air filter that your home uses - go cheap and replace more frequently rather than going expensive and hoping it lasts longer. Also, vacuum and dust regularly. Level 2 - bang-for-the-buck is the Corsi–Rosenthal box - and it will always be what I recommend to people who are trying to figure out if air filters will make a difference for them. Level 3 - buy the system that moves the most amount of air and has replacement filters that don't cost an arm and a leg. Levoit, Winix, Blueair, are all honestly decent systems - and if you open them up to replace their filters, you find out that they're really just doing the same thing the Corsi-Rosenthal is. They're just intake fans sitting on top of a filter. As price goes up, you're really just paying for things like automation (fan automatically ramping up when it senses high particles), noise reduction, filter change nagging, etc. My suggestion is to buy whatever goes on sale next time and stick with the brand/size for ease of maintenance. Minimum size I'd recommend is 1000sqft even if your home/room is smaller than that. The max room size is calculated by their highest fan speed - chances are, you probably won't be running it that high all the time. It is better to get multiple smaller units that are local to the area you're using versus a single large unit for a big space. These do not move air vigorously (less than your standard fan) - so even if they say they'll do "3000sqft" - they are assuming you're in a single rectangular room with only four walls. If your home is 2000sqft with lots of rooms and hallways, a single unit will not work. However, the number one thing about any air filter is that they are a continuous cost and will only work as long as you are regularly replacing their filter media. At least with air filters you will be able to see exactly what they're doing when you replace them - mine are usually pretty grey-looking by the time I take them out. Oh, I wouldn't bother with all of the fancy filters (like pet, charcoal, or whatever) unless you have a very specific need for them. Those are are mostly gimmicky. Air quality monitors (like the Airthings) are also not needed - and in fact, many of the higher end filters have particulate sensors in them. It's mostly informational for people like me who just really wanted to know if all of these filters actually did anything. Plus, AQ monitors don't tell you *what* the stuff in the air is, they just tell you it's high. I found out that vaporizing humidifiers make PM sensors show deep red spikes because they're literally throwing tiny bits of water into the air (but it's not specifically a negative thing - especially when you're trying to raise humidity). For the "do they work?" question, my answer is "Eh... sorta." They definitely help with things like odors (such as from cooking or pets). I have not noticed a huge decrease in dust build up (but my house is not sealed in any shape). I definitely notice that my allergies get worse when I go outside versus hiding in my house, but it's not like they're completely eliminated when I'm home. So for me at least, they help, but they're not some sort of miracle cure that'll magically fix everything.