https://scosman.net/blog/using_in_wall_computer_fans_for_hom...
There's also systems which can move air both ways through the whole house - https://www.ventilation-alnor.co.uk/index/support/alnor-know...
Your DIY solution looks a lot cheaper though.
Recently a daughter moved into a really nice apartment close to a major university/freeway where she will live for the number of years it takes to get a Phd. I got concerned about tire dust. So I am about to start building a really nice air DIY air filter using eight Noctua NF-P14s (about 1000 cfm). XMas present.
I really wanted to use merv-13, but got quite worried about air flow restrictions, plus cost to replace (assume monthly). Instead I went with two 12x24 Carter reusable electrostatic merv-8 filters. I use Carter filters on my house blower, and really like them (just washed them... scary how much junk is in household air). Also, I got the 12x24 direct from Carter for a very low price as they were returns. Note: This is NOT a low cost project, but I just got scared re: merv-13 so went with what I know.
Anyway, the final product will NOT be like this guy's DIY. I will use my somewhat decent woodworking skills to fashion a good looking standing "lamp like" appliance that should look good in most living rooms. I am thinking of going with knotless cedar as I really like working with cedar, and there are some mills here in NW WA where one can go to get such wood (not a HomeDepot specialty).
My question is whether an electrostatic merv-8 filter would do well with tire dust. I am not looking to create "clean room" conditions in the apartment. Just get rid of some of the bad stuff. I am very weak re: understanding filters, mervs, etc. APPRECIATE any insights. Thx, RF
At some point I found a nice chart, IIRC from the EPA, showing the efficiency plotted vs particle sizes for a variety of filters. IIRC the filters generally split into two categories: those with decent efficiency all the way down to zero microns and those with very poor efficiency at small sizes. IIRC the split was around MERV 12. Obviously your filter is not the filter in the chart.
So I would go with MERV 13 or even a bit higher. Also, keep in mind that pressure drop is related to the velocity of air through the filter, so a physically larger filter will have lower pressure drop at the same flow rate. But the need to replace a filter is related to collected gunk per unit area, so doubling your filter area will cost twice as much but last twice as long and will use less power and run quieter.
Also, electrostatic filters can lose their charge from exposure to various contaminants.
edit: it was the chart here, also mentioned down thread.
https://www.frdmtoplay.com/nagivating-air-purification/
Portable Air Cleaners, Furnace, and HVAC Filters. 3ed. EPA 402-F-09-002
And I remembered a bit wrong. Even MERV 10 will pick up the smallest particles, but MERV 8 may miss some. But for good performance at the most penetrating size, you want MERV 12-ish. For a single-pass filter (filtering outdoor air as it enters), you want much higher - MERV 16 or even HEPA or near-HEPA, if you want acceptable performance against potentially nasty outdoor conditions due to wildfire or nasty human particle sources.
I would stick with merv-13 because you'll get solid performance across a lot of things you might want to remove, from viruses to general pm2.5 and things like volatilized cooking oil. Clean air is awesome and tire dust isn't the only thing that's annoying.
The lead line for this article pretty much reflects the reason for my post: "The air purifier marketplace is an apt metaphor for how a particle must feel while being trapped in a filter - at every turn there's a new acronym or regulatory agency or purifier type."
In any case, if you see lots of gunk, that’s not the hard-to-filter stuff. I can say, as the proud owner of a monstrous HEPA filter with a dirt cheap noting-special MERV 8 pre filter and an utterly boring metal louver before that, all continuously collecting outsize air, the louver gets a bit gunky, the MERV 8 filter turns black after a while, and the HEPA filter is indistinguishable from brand new. This whole system replaced an older “ISO ePM1” (yes, the manufacturer conveniently forgot the number after that, but it’s MUCH higher spec than MERV 8), and the indoor air quality as measured by a little particle sensor suggested that the ePM1 filter missed about 50% of the outdoor PM2.5, whereas the new system produces air that measures zero across all particle sizes. And that ePM1 filter did a fine job of turning black :)
Get a particle counter and test your system!
P.S. the HEPA system uses less power and will cost less to operate over time because it is HUGE but has the same flow rate.
vid of the noise levels https://youtu.be/wOc0TM1ErYA?t=195
1. Are box fans just really terrible? I would expect the amount of airflow from a box fan to absolutely demolish these little case fans.
2. Does airflow not actually matter that much? Assuming the box fan really does move far more air, that would imply that air filtration is somehow not driven by air flow. Or else the testing methodology is flawed.
Computer cooling fans also might not have been designed to handle that much "load", but in the case of the box fan, we have an actual report of someone who almost burned down the house:
AFAIK PC fans are designed to move air at low pressure while quality air purifiers are designed to handle more pressure.
Other than that, it’s a neat writeup. Would like to see a follow-up with static pressure considerations.
https://www.amazon.com/dp/B01728NLRG
Quiet, efficient, works super well
but 5x arctic cooling PC fans is ~$100. the commercial versions are easily available, more effective, no more expensive, and don't look like a box of furnace filters taped together.
But I'd honestly pay a premium for a commercial air purifier that just has a bunch of 120mm/140mm fan mounts instead of their "maybe tolerable at Very Low" integrated box-fan equivalent.
In general, all I've learned from online reviews of "quiet" appliances is that different people have very different definitions / criteria for "quiet".
i also have iqair which according to reviews is quiet at low speed. in my experience this quiet sounds like airplane (i got it replaced once. apparently it's just the way it is).
https://old.reddit.com/r/crboxes/ is a good resource if you're looking to make your own. There's been a general shift from large box fans to PC fans because their performance/noise ratio is better.
With the fans blowing in, all the dust is on the inside of the box (and on the fans).
The box fan version also blows air into the box
embarassing
Regardless technology is often named after people who made it popular, especially when original inventors are unknown or too diffuse.
i build one like this back in 2018 during california fires. used it mostly in garage for filtering air when i work on "things". decommissioned it last week.
i guess i am not the only one who came up with this idea prior to covid as this is pretty obvious
other refinements were using a shroud to prevent back flow
you don't need a lab to figure out that replacing 1" filter with 4" filter and even better arranging multiple filters in a box will improve flow rates and filtration (especially for box fans that not really designed for static pressure)
corsi&rosental work, imho, is equivalent to lab work reporting that you can move more water through 10" pipe than through 1" pipe.
hence extra research by Corsi and Rosenthal is needed. After they will do the measurements they can be declared as inventors of p100 masks, that will be known as Rosenthal-Corsi masks