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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8/24/2020 09:34:25 pm
12/8/2020 07:01:57 pm
Doubling the area decreases the air velocity in half which lowers flow resistance by 4x. Flow resistance is inversely proportional to the square of the filter area.
11/6/2020 11:33:43 am
Great test, thanks for documenting all of it. I am happy to see these articles and conversations about using the best air filtration to improve indoor air quality, without affecting air flow or straining your system. MERV 13's are a much better options than using a MERV 8 and 11 stacked on top of each other.
11/26/2020 03:26:44 pm
I read many of the reviews of the Lasko fans and I will NOT be purchasing one...apparently, too many of them have a whiny pitch that varies over time and too many of them fail shortly after purchase.
12/8/2020 06:58:39 pm
The Lasko fan is quieter than the Powermatic PM1200 air cleaner system. See the dB measurements in the test document. I don't find it noisy or annoying at all. I guess you could use a furnace squirrel cage blower and put some foam on the outlet to quieten it down. But, if you do that you will get about half the performance of this system.
12/20/2020 09:17:29 am
How do you position your filtration system? I am thinking of putting it on a rolling cart so that it can be near where I am working. What size workshop did you perform your tests? The larger the shop the more cubic feet of air that needs to be cleaned. Do you have a recommendation for filtration size versus cubic feet of the shop?
12/22/2020 01:39:13 am
William, it doesn't matter which way you point it or where you put it... the performance will be roughly the same.
4/22/2021 01:26:23 am
It's great to learn that you can get great filtration if you pay attention to the surface area of the filtration material. My husband and I would like to make sure that his workshop has breathable air. Maybe we should also look for a UV blaster to make sure that any pollutants in the air won't harm his body.
9/23/2021 10:45:16 am
I want to make sure that my workshop has a good air system. It makes sense that I would want to get a professional to help me out with this. They would be able to ensure that my workshop has clean air to breathe.
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