Ever wonder what the best air filter is? I spent $2000 to find out!
Part 1 To start this series, I tested single filter + box fans and the DIY standard Corsi-Rosenthal design. Eleven types of filters were tested from 6 different manufacturers including 1″, 2″, and 4″ filters.
In this video I cover the best filters for a 4 cilter Corsi-Rosenthal box as well as theoretical performance for your home HVAC. I used smoke to test with because it is an easily repeatable method for testing the filters on a level playing field.
For you home HVAC be sure to replace high MERV filters at the 2-3 month range because if there is not enough airflow for your furnace, it can be damaged. If there is not enough airflow in the summer your AC can ice up. In the winter too much heat can build up in the system can it can potentially crack the heat pipes and leak natural gas fumes into your home. If these are not issues you want to deal with, go with a low MERV filter for your HVAC and run alternate filtration options (like DIY filters or HEPA filters) elsewhere in your home to clean the air to a desired degree.
Part 2 Coming Soon! In this video I talk about what makes a great filter for your DIY build. The Model-A and Model-B filter kit results are in and they are POWERFUL. I also test a few new single filter options and answer some questions from the comments.
Filter Performance Charts
Chart Details
This first chart covers the performance of the 4 filter Cosri-Rosenthal style filter box. All results are with an Air King box fan.
The Thin Green bar indicates the configuration’s theoretical monthly filtration capacity in # of incense sticks. This number is based on how quickly a DIY air purifier is able to remove 1 stick of incense from the air in the room and how many of them can be sequentially removed from the air in one month’s time. For additional information, the smoke from 1 incense stick is roughly equivalent to the smoke created by burning 3 cigarettes.
The Thick Blue bar in the chart is the cost of filtering 10 sticks of incense from the air. This value is obtained by dividing the total cost of replacement filters for a given configuration by the monthly filtration capacity then multiplied by 10.
The most effective filter is has the tallest thin green bar. The least expensive filters to operate have the smallest thick blue bar. Filters with a high green bar and a low blue bar are the best preforming filters.
For example, the 3M MERV 14 is the best in the test and the Aerostar MERV 11 is the worst performer. That said, the initial cost of the filters is often a factor and this cart is more about how much efficient the filter is per $ spent, not what filter is the cheapest. In the end you may find that a less efficient filter is the right price for your budget, and that’s ok.
Another thing to note is the K&N filter on the far left of the chart. These have some of the highest initial costs but because they are washable, their long term cost of operation is by far the lowest cost option. This is true for all configurations, single filter, CR, Model-B and Model-A. The left blue bar indicates the cost of the filter on the first use. The right blue bar indicates the cost of the filter after 5 years of use (20 washes).
The above chart covers single HVAC filters taped to the back of a box fan, the most simple DIY air filter design. These offer the lowest introductory costs but do not filter better than the worst preforming Cosri-Rosenthal configurations. The best in the test is the 3M MERV 14 filter on an Air King box fan. Using a low cost, low powered box fan like the Lasko 20″ (or most all-plastic box fans) not only lowers performance but it also increases cost of operation in the long run. If you are using a low powered box fan you can expect 30% less air flow.
In order to get a good baseline for the DIY filters I tested 4 professional HEPA filters. These filters are considered undersized for the 2 car garage with high ceilings where they were tested, but I think it’s helpful to know what to expect from a HEPA filter in a worst case scenario. All these purifiers are more expensive to purchase and operate than the DIY options.
That said, if you want to run HEPA filters in your home all of these are great options. If you have one large space you want to filter then the Air Doctor or the Blueair 211+ are the best options. The Blueair is less than 1/2 of the price of the Air Doctor and the lower cost of operation is negligible over time. The same can be said for the Honeywell and the Levoit filters. You can get 5 Levoit or 3 Honeywell filters for the price of 1 Air Doctor. In the end if you have 5 small rooms you want to filter, get the Levoit. If you have fewer, larger rooms to filter, the Honeywell is the lowest upfront and long term cost off all. I do not recommend any of these filters for removing woodworking or industrial dust, the filters clog quickly.
A video will be out with more detail on this test soon.
I have been using all of these in my home and can recommend all of them. There are links for these filters below. Buying anything from them helps support this research.
Air Doctor 3000: https://amzn.to/3I1VImF
Blueair 211+: https://amzn.to/3lrVc9Y
Honeywell HPA 200: https://amzn.to/3E79V0y
Levoit Core 300: https://amzn.to/3HZHXoz
These are the results for the Model A and B air filter kits. Please note that the maximum number of incense sticks that can be filtered by the designs have been scaled to a maximum of 2000, up from the 1200 in previous charts.
The Model-A tends to cost more to operate because it uses 8 (16x20in) HVAC filters rather than the 4 larger HVAC filters in the Model-B (20x30in).
More data on these is coming soon! The video for these is currently in the works.
LINKS to FILTERS and FANS
FANs (For all versions):
Enclosed Motor Caterpillar 4000CFM fan (black) https://amzn.to/3TD9NM3
The original 3000CFM Maxx Air Fan (orange) https://amzn.to/3fXokQC
Lasko 20in Box Fan (best Corsi-Rosenthal price): https://amzn.to/3c3nVNF
Air King 20in Box Fan (best Corsi-Rosenthal performance): https://amzn.to/3Tbzl1O
MERV 14 FILTERs (best small particle capture):
Nordic Pure 20x20x1 (12 PACK): https://amzn.to/3O6GGgr
Nordic Pure 20x20x1 (6 PACK): https://amzn.to/3o5Ge7E
Nordic Pure 20x20x4 (1 PACK): https://amzn.to/3AYyiwC
3M Filtrete 20x20x1(2 pack): https://amzn.to/3duBAxY
Nordic Pure 16x20x1 (12 PACK): https://amzn.to/3MqxJ1c
Nordic Pure 16x20x1 (6 PACK): https://amzn.to/3Oy9NLg
3M Filtrete 16x20x1 (2 PACK): https://amzn.to/3fsenNQ
MERV 13 FILTERs (almost the best small particle capture):
3M Filtrete 20x20x1 (4 PACK): https://amzn.to/3c5wZlu
Filter Buy 20x20x1 (4 PACK): https://amzn.to/3wdtCjk
3M Filtrete 16x20x1 (4 PACK): https://amzn.to/3RjkH7B
AIRx 16x20x1 (9 PACK): https://amzn.to/3S4y8Zt
MERV 12 FILTERs (good small particle capture):
Nordic Pure 20x20x1 (6 Pack): https://amzn.to/3O6HaTN
Nordic Pure 20x20x4 (1 PACK): https://amzn.to/3crRhpm
3M Filtrete 16x20x1 (4 PACK): https://amzn.to/3y2vgW6
Nordic Pure 16x20x1 (6 PACK): https://amzn.to/3D3M2GY
MERV 11 FILTERs (minimal small particle filtration):
K&N Washable everlasting filter 20x20x1 (1 PACK): https://amzn.to/3e9MDNn
Aerostar 20x20x1 (6 PACK): https://amzn.to/3q9Z0M4
K&N Washable everlasting filter 20x20x1 (1 PACK): https://amzn.to/3Vq7oWv
K&N Washable everlasting filter 16x20x1 (1 PACK): https://amzn.to/3Vq7oWv
3M Filtrete 16x20x1 (4 PACK): https://amzn.to/3TFlnH8
Filterbuy 16x20x1 (4 PACK): https://amzn.to/3g8Diqe
MERV 8 FILTERs (for large dust particle collection only):
Nordic Pure 20x20x1 (6 Pack): https://amzn.to/3Rz9T6G
Nordic Pure 20x20x4 (1 PACK): https://amzn.to/3IPFSM1
3D PRINTED PARTs (Build at your own risk):
Air Filter Clips: https://www.thingiverse.com/thing:5366495
Drum Fan Edge Clamps: https://www.thingiverse.com/thing:5501226
BUY 3D PRINTs (if you don’t have a printer):
Air Filter Clips: https://www.etsy.com/listing/1210663842
Drum Fan Edge Clamps: https://www.etsy.com/listing/1287743212
Air filter Clip Wrench: https://www.etsy.com/listing/1323881337
GAFFER TAPE (best option for taping up your Corsi-Rosenthal):
Better than duct tape for this use https://amzn.to/3AR6E4Q
DIGITAL ANEMOMETER (use one of these to test your own air filter):
For testing wind speed https://amzn.to/3OkzmhF