Using filters on box fans

[Phil Thien]

I had someone write recently and ask "how well do those filters strapped to box fans actually work?"

I thought it deserved some more research, and I've been trying different filters, etc., to figure out how well a box fan w/ filter can function as an air cleaner.

Because I didn't intend this to be permanent, I wanted a quick way to hold the filters to the fan.

I was able to weave a piece of clothesline through the grill in such a way that it retains the filter in three corners. The fourth corner can be tied in a bow, or you can use on of the cord stops I found on an old bag that was being discarded.

It actually works very nicely, and took all of two or three minutes.

[Jack Wilson50]

Paul:

Any feedback on which type of filter works best?

Thanks for the research.

Jack

[Larry Prem]

Most air cleaners are two stage. The other filter is 5 micron, the inner 1 micron.
With just one filter you are either sacrificing efficiency, or the filter will clog faster.

A filter on a boxfan is not on par with an air cleaner. It's certainly better than nothing, but I would not spend any time optimizing it.

[Van Huskey]

Here is some info (though somewhat hard to interpret) about using box fan filters.

http://www.americanallergysupply.com...ir-cleaner.htm

[Phil Thien]

Most air cleaners are two stage. The other filter is 5 micron, the inner 1 micron.
With just one filter you are either sacrificing efficiency, or the filter will clog faster.

A filter on a boxfan is not on par with an air cleaner. It's certainly better than nothing, but I would not spend any time optimizing it.

Larry, the question wasn't which one works better.

The question was, "how well can a box fan work?"

[Sid Matheny]

"how well do those filters strapped to box fans actually work?"

From the looks of the filter on my fan they work well. Not like an air cleaner of corse but they do help. Anything that filters dust out of the shop air is a help. Several work better than one but just one in the right place can make a big difference.

Sid

[Van Huskey]

This does pose the question how well a box fan based filter would work if equipped with a proper pre-filter system and a pocket filter for the fines. They are about 2000 CFM (with no static pressure). I have considered building one or two into the walls between my shop and my "mechanical" room. There ain't any magic to air filtration just movin' air through filters.

[Phil Thien]

This does pose the question how well a box fan based filter would work if equipped with a proper pre-filter system and a pocket filter for the fines. They are about 2000 CFM (with no static pressure). I have considered building one or two into the walls between my shop and my "mechanical" room. There ain't any magic to air filtration just movin' air through filters.

An axial fan won't likely pull much air through two filters.

I noticed a huge hit to CFM just placing a filter in front of the box fan.

The 20" Lasko fan I'm using claims to move 2500-CFM free-air, on high speed. I'm guessing it moves about 500 to 750-CFM early-on with a "higher-end" Filtrete filter (on that same high speed). That is pure speculation, mind you. Measuring it would be a challenge.

But a couple of important points: The filter I'm using is 20" square. About 40% larger than your typical Jet air cleaner (12 x 24 or 288 sq. inches). So it may actually be doing a pretty decent job.

Only time will tell how the fan will handle a filter as it gets loaded. That is what I'm working on now, I'm pre-loading filters.

If I was a betting man, I'd say two box fans with quality filters may five an air cleaner a run for the money. But my mind may change once that filter starts loading.

[ian maybury]

The issue Van/Phil could well be in the last point 'just movin air through filters'. Not saying it's definitely an issue as i've no experience and have never investigated them, but the so far as i can remember axial flow fans typically only generate a few inched if that of static pressure. Which unless the filter was very low pressure drop over its life might possibly lead to flow problems.

ian

[Van Huskey]

My thought would be to use a pair of fans with a common plenum and one set of LARGE filters from Filters America for tons of surface area. The idea being I am doing it for fun and if it doesn't meet expectations all I have to do is take the box fans out and build in a proper fan.

[Ole Anderson]

For a while I used a 1/12 hp 24" box fan with a cheap Merv 4 pre-filter in front of a filtrete filter. It worked, but the air flow is a small fraction of what the fan put out without the filters and a small fraction of what an ambient air cleaner with a 1/3 hp centrifugal fan can generate. And having to run it on HIGH all of the time just to have any airflow at all was an annoyance regarding noise. I have since moved on to a DustRight ambient air cleaner and a full dust collection system powered by a 2 hp Dust Gorilla.

[Alan Schaffter]

After looking at the dust in my shop during and after completing recent project, I have decided, that my dust collection system with 3 hp motor/14" impeller, 3D Pentz cyclone, efficient ducting, dual parallel filters/direct vent, fancy auto gates, central shop vac for routers/ROS, ambient air cleaner, etc., etc. only go so far, maybe not far enough. I still generate dust in various ways that is not collected. The solutions- a good mask or live with it. I'm living with it.

[Mike Heidrick]

I use this method for spraying out of rattle cans. I use el cheapo the cheapest filters I can find. Simple tape on. Works awesome.

[michael veach]

Don't leave the fan running unattended. The motor can become very hot due to the reduced air flow.

[Greg Peterson]

I still generate dust in various ways that is not collected. The solutions- a good mask or live with it. I'm living with it.

IME, ample DC capacity is only half the battle. The real struggle, in my opinion, is getting the DC as close as possible to the cutter creating the dust. I believe the euro machines do a good job of addressing this issue. What passes for DC collection on most of the machines I have seen, it appears most manufacturers give DC little thought.

I got rid of my DeWalt RAS. I did not get anywhere near what I put into it, but I simply could not tolerate the mess it made. And I tried numerous DC techniques and shop made hoods.