[OP]
Contributor
I'm looking to build or buy an air cleaner for my shop. I notice some build videos on youtube use attic air fans and the like. Anyone have any input on good choices/bad choices on this? They seem to pull more than enough cfm's. I'm trying to keep the costs down so I don't want to be over $75 for the fan. Do I put myself into the land of quick dying crap at that price?
Member
Search ebay and craigs list for electostatic smoke eaters. These were used to filter cigarette smoke from bars and restraunts back when it was legal to smoke in such establishments. I picked up my smoke eater for $200 off ebay several years ago. It was a $1500 unit new. They give the air going through the filter a high voltage negative charge. Then the air flows through a set of positively charged plates and all the micron sized particles stick to the positive plates like glue. I periodically pull the positive grid, thoroughly wet it with 409 then hose it off (Running the positive grid through the dishwasher also works great!). It is amazing the amount of incredibly small particles it collects! It is by far the best shop filter I have ever seen! It is also great for cleaning up the air when I am welding.
Last edited by Mike Schuch; 09-22-2015 at 12:18 AM.
Contributor
John, try this ... a ordinary 20" fan with a 20" filter attached to the suction side ... it'll surprise you.
Julie Moriarity did a test study on air cleaners that you should be able to find.
I had already had mine up for two years at the time she did her evaluation; and I knew what kind of results she was going to have.
After about 6 months that the ceiling fan was up; I decided since it worked so well that I would set-up a floor model that has, also, worked-out very well.
A lot of the 'fines' that I was letting float off-and-around were from hand operations that seemed trivial and the occasional use of the jig saw.
After a few weeks there was a noticeable brown shade to the filter. I use it even when I use the ROS at the down-draft table: set-it-up-on-top adjoining the work.
I paid $20 apiece for the fans and use MERV 7 filters that I clean about 3 months to ensure they sustain ability to pass air.
And btw ... I am rabid about dust collection ... basement workshop ... ClearVue DC ... 4 shop vacs ... and a plenum filter on the house system.
Contributor
Mine is mounted from the ceiling and I can swivel it for changing direction but it works pretty good for an air cleaner (fan is mounted upside down so I can easily reach the switch). Total cost was about $35.
Shop air cleaner - 2.jpg
Shop air cleaner - working.jpg
David
CurlyWoodShop on Etsy, David Falkner on YouTube, difalkner on Instagram
[OP]
Contributor
I appreciate the responses. Sam, Dave, my understanding was, from threads here, that ordinary fans like that don't do the job. My memory is not enough cfm's and once the filter got a little dust on it no air pull.
Member
A squirrel cage fan is much more suitable to moving air through a duct or a filter. I have a unit, designed for cleaning air, mounted to the ceiling of my shop that I bought years ago from Grizzly. Mine cleans the whole shop full of air every six minutes. I paid $175 for mine.
No PHD, but I have a DD 214
I built one using a gable fan that is rated at 1650CFM. this is greatly reduced once it is put into a fixed airway with filters in the path. As John F mentions above, if I were to do it again I would use a squirrel cage fan. As others have mentioned, even with a cyclone for the machines there are plenty of activities that don't involve machines. I also use a vac with a Dust Deputy for hand held power tools and I am amazed at how much an ambient cleaner picks up during some operations.
"A hen is only an egg's way of making another egg".
– Samuel Butler
Member
I built mine around two Dayton 10" axial fans rated for 665cfm each (search ebay for dayton 10" axial fans, I see some there now for $59ea). As Glenn stated above this type of fan is not very good at overcoming static pressure and when building it I was figuring it would move about half the combined cfm (600cfm+-). The best I can tell it's actually moving about 300-400cfm passing through a 24"x12" electrostatic pre-filter and a 24"x12"x12" one micron pocket filter. At that rate the air in the shop (22'x22'x9.5') would be cycled through it about every 12-15 minutes. Not quite as fast as recommended but I find it acceptable and the Dylos meter seems to confirm this. They are quiet too, nothing more than a little white noise.
I have a 1,2,4,8 hour timer on it and always have it running while making dust and for eight hours after I leave. I can tell you it does capture quite a bit of fine stuff, especially the pre-filter. When I clean it, first with compressed air and always outside, the amount of super fine dust is impressive. I'm sure a squirrel cage fan would move more air and work better but...
Last edited by John Donofrio; 09-22-2015 at 9:59 AM.
Member
i think the ultimate homemade one is using a wynn nano 9l cartridge filter and a inline blower fan motor. seal off one end of the filter place fan on a seal on the other end and maybe add a swivel so you can direct the air flow as needed. bill pentz's website has a more detailed description on how to build it.
[OP]
Contributor
What is the advantage of the squirrel cage fan?
Member
to make a reasonably cheap air filter, would it work if you took a 1 micron dust collector bag, and fit it over the output from a squirrel cage setup?
As best I understand it a centrifugal (squirrel) fan will develop much more static pressure than an axial fan. In a ducted environment (like in a tube, duct or air cleaner housing) the ratio is about 5 to 1 in the ability to shove an air mass through a restrictive space. The usual cornucopia of variables and ranges of actual numbers applyOriginally Posted by John T Barker
"A hen is only an egg's way of making another egg".
– Samuel Butler
Contributor
Whatever you build use a HEPA filter or equivalent MERV rating. Otherwise you will remove some coarse particles but continue to circulate the fine (read potentially health harmful) particles around your shop. I bought a HEPA filter from Grizzly and built my own fine particle filter using a squirrel cage blower I had lying around. It helps clean the air but is no substitute for dust collection at the source.
John
Moderator
The squirrel cage style fans are more powerful at moving air through filters. The box fans choke down easier. However, the squirrels are heavy and bulky and are usually mounted to a wall or hung from a ceiling.
The box fans are arguably more mobile and can be positioned near the point of purchase. I used box fans with filters for sanding and rasping and they work extremely well.
Member
A squirrel cage fan produces much more static pressure than a propeller fan does. That is why they are used in your furnace or in any ducted system, including dust collectors. Propeller fans should not be ducted and work best when not obstructed in any way... like with a filter. Squirrel cage fans are usually quieter also.
No PHD, but I have a DD 214
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