Several weeks ago I presented the test results from tests of 10 different air filtration systems. The results were amazing and a $100 DIY system beat the $500 Powermatic PM1200 air filtration system by a pretty wide margin. You can read that article HERE. Below is a summary of some of the performance results from that article. Particle counts were logged using a laser particle counter. All tests were performed by cutting about 12 ft of ½” MDF and 12 ft of ¾” melamine on a table saw with the blade elevated 2” above the stock (to create more dust). For reference, the green band at the bottom of the graph is where you want your shop air to be for a healthy environment. Anything above that band is unhealthy.
I learned a great deal during the air filtration system testing and I'll distill the most important findings in this article. I learned enough to design a system that you can build yourself that will outperform the equivalent of two $500 Powermatic systems! Next week I'll present the Shop Hacks Ultimate Air Filtration System in a "How-To" article.
This article is laid out as follows:
How many filters are ideal and why?
The surface area of your filtration material matters. It matters a lot. Each time you double the filter material area you cut the flow resistance at any given flow rate down by 4x. If you increase the filter area by 4x you decrease the resistance 16x. Increasing the filter area by 10x decreases the resistance by 100x. You get the point... put mathematically, the flow resistance at any flow rate decreases as the square of the filter area.
What does this mean in practical terms?
For a 20" box fan the flow using 1, 2 and 4 @ 20"x20"x1" new (clean) filters is...
For the Lasko High Velocity Fan
As you can see, the benefits of adding more filters drops off after two filters. However, dirty filter will have about 2x the resistance of a clean filter. This means
So, a 4 filter system with dirty filters will perform 35% better than a 2 filter system with dirty filters. I have a 3 year old, 4 filter system in my shop and I've only swept the filters a few times and it still performs very well. It is nearly a no-maintenance system.
For this reason, the Shop Hacks Ultimate Air Filtration System will be modular. You can use 2,3, 4 or 5 filters with it depending on your budget preferences. That will allow those who want to save some $$ to use just two filters and those who want the least amount of maintenance and the highest performance to use 3, 4 or 5 filters.
What Fan and Filters Should You Buy?
After running the Air Filtration Shootout Tests I realized that lower MERV ratings do not mean that filters will have lower resistance to flow. In fact, THIS filter, when clean, has a lower flow resistance than ANY filter I've tested, including cheap fiberglass filters. I found this test data to back up this notion...
So, the stacked MERV 8 and MERV 11 filter configuration that I used in the Air Filtration System Shootout was both more restrictive and filtered fewer particles than a system using THIS filter alone. I'll link to the fan that I'll design the Shop Hacks Ultimate Air Filtration System around below also.
I look forward to presenting the Shop Hacks Ultimate Air Filtration System design and a link to the plans to you in next week's article. If you have any questions in the meantime, please leave them in the comments section below this article! I'll be happy to help you out.
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