First bigger surface area two you can run it backwards each time you power it on and the filter increases time between automatic cleaning and helps with dusty environments.
It’s more a function of surface area to volume ratio of the filter. More surface area to volume means more energy is lost due to flow friction between the air and filter walls. However the trade-off is that a higher surface area to volume ratio results in higher filtration efficiency so you have to optimize between flow rate and filter efficiency to get a
overall optimum filtration performance.
Feel the air coming out, vs without a filter. The slower the air is, the fewer opportunities you get to trap each dust grain. Overall miss rate improves exponentially with airflow speed.
Filter's airflow restriction is primarily a function of surface area and filtration medium layers. More surface area results in a better airflow and more filtration medium layers results in a worse airflow.
To maximize surface area of a filter, you can get a thicker accordion filter. This will generally provide good airflow and filtration characreristics.
Sorry about video links below, I liked them at chart times, so you don't have to watch the video to check out the summary.
Here is an example of airflow restriction vs filter. Note that 4 inch Honeywell filter only provides small static pressure rise over no filter option: https://youtu.be/RkjRKIRva58?t=456
Thicker filters cost more, but also last longer. General rule seems to be that when you double the filter thickness, time between replacements doubles as well.
Fan and then filter could lead to the fan blades getting dirtier faster. Other than that, I'm not sure if it makes a difference as far as effectiveness.
To let air pass the filter easier, bigger surface is encouraged - bigger area, for the same pressure difference less flow per unit area. Why not to have two circular filters, on each side of the mask?
One is you are running the same air through the filter all day.
The other is you are using a vacuum cleaner that is sucking up dust from the floor and pumping out that air.
I assume in the vacuum cleaner case, you are better off with a higher performing filter since you need to trap that dust on first pass through, whereas with the filter that is circulating the air all day, you get a "second chance" to capture a given particle?
It isn't just a backup; you want it there before the expensive fine-grained filter, to catch the big stuff and extend the life of the more expensive filter.
putting it on the intake keeps the motor cleaner (which will help with motor life), you can vacuum the filter without disassembly, and the air flow will tend to help the filter stay on, instead of pushing it away.
What benefits do you feel from having four filters? Not hating, genuinely curious. It's just never occurred to me to filter the air in my home aside from burning something on the stove or similar
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