Just go to Amazon or eBay. As
@duneslider said the powertec is $149 on Amazon, WEN versions can be found for a bit cheaper.
These are 400 CFM units, not the larger CFM units. They also typically have 5 and 1 micron filtration at those CFM rates.
Well, the filters are needed no matter and disposible, most people have a box fan laying around. With 15 seconds of shopping I found 20x20x2 filters for $10 each. So about $80 all in.
A cheap Grizzly is $160 and up. The better ones, Grizzly and Jet are $500.
Sure it isn't a fantastic deal, but not as bad as your numbers.
I'm not sure we are comparing similar performance. Are the $10 each filters MERV 13? I found MERV 8 for that kind of price but then you don't get nearly the same level of filtration. To get down to 5 micron I believe you need to get to a MERV 13 which will up the cost to what I was finding.
As for filters, yes they are consumables but when you buy the air filtration system you get the original filters with the system. The 1 micron portion of those systems are typically reusable but the 5 micron would need regular replacement. For the home built box you need to buy the filters first but then replace all of them in an ongoing basis. It seems like long term replacing 1 filter will be much cheaper than replacing 5.
As for the "better ones" I believe you are talking about units that have much higher CFM, and yes, those units are much more.
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One particular issue I read about with using a box fan is that although they have an impressive CFM capability when unencumbered, the CFM drops dramatically when you restrict airflow. For this reason
@PoorUB solution should work much better at actually cycling the air and if you have access to the things he describes it might be a great solution. It would potentially not have the timer and other functionality of a cheap air filter box and I suspect might also be larger but I also suspect it might out perform the cheap air filter boxes.
Ultimately a box fan with a filter on it will work to clean the air and if whatever anybody does makes their lives better that is great. I tried the box fan/filter approach and it just wasn't effective enough for me. I'm looking to get rid of fumes more than get rid of wood dust so a higher CFM seems critical to me. I already have an exhaust fan the can empty out the shop after about an hour of running but that results in significant heat/cooling loss as conditioned air gets replaced by outside air. I continue to contemplate the cheap air filtration systems but I remain weary of whether I'd be satisfied with them. I do suspect the more expensive higher CFM systems would make me happier from an air quality standpoint but I don't like the cost of them. Perhaps I need to search out a
@PoorUB solution.