What's a decent air cleaner for my shop? 25x25x15

[Mike Dowell]

I made an air cleaner leveraging the Bill Pentz design. It works quite well and should be adaptable to a cylindrical filter of virtually any specification. I used a Wynn 2N230NANO filter which is rated Merv 15, not a HEPA rating. HEPA (High Efficiency Particulate Air filters) is typically a higher Merv rating (17-20) than my unit. One feature I added was a timer to allow leaving it on after I leave the shop knowing it will shut off. I leverage the same Nano filter (a pair of them) for my dust collection system.

While I like the mobile design it adds a degree of clutter to my small shop. I have been thinking about building it into (under) my layout table.

How do you clean the filter? Just blow it out with an air line from the inside?

[Mike Dowell]

I am in the process of designing the new shop so I don't have this up and running.

This is the air cleaner I am talking about:

http://www.honeywellstore.com/store/...r-purifier.htm

I have used several of these in the house over the years and they are very good. Amazon seems to be OOS at the moment but you can usually pick them up for $135-150 shipped.

I plan to use 4 for my 1100 sq ft shop and mount three off them at about 8 feet on 3 different walls either on shelves or on top of cabinets. I will have a 4th buit into a rolling cart that I can move near me when sanding etc.

I plan to wire the 3 wall units onto a circuit run by something like this:

https://www.zoro.com/intermatic-elec...0w/i/G1927256/

That will allow me to run them constantly when in the shop and leave them running for a specific time when I leave. This gives you all the functionality of the standard units except remote control which you could do if you liked but I feel unneeded since you don't turn them on and off a lot. 3 of them are equal in air movement to the oft-recommended Jet and cost only a little more and are true HEPA filters.

Van, do you actually have to replace the filters, or can you just clean and reinstall them? If I went this route, do you think at a little more than half the size of your shop, I would be good with two of these units?

I'm trying to decide between this and the one that Bill Andersen posted up.

[Mike Weaver]

How do you clean the filter? Just blow it out with an air line from the inside?

Yes, after taking it outside first. Another reason for the floor versus ceiling.

[Bill Adamsen]

How do you clean the filter? Just blow it out with an air line from the inside?

I actually use an electric leaf blower. An air line might produce too focused a pressure which could blow out a pleat and permanently damage the filter. The filters are expensive (about $200 including shipping) so avoiding damage is prudent.

[Bill Adamsen]

This idea seems to be a great way to go. Have either of you ever thought of hanging it from the ceiling, and blowing it down to push hot air lower to help with heating in the winter? Not sure it would work, or if it would reduce the designed function, but if it did, you would be getting twice the bang for the buck.

The output is really strong and I use the adjustable 90°on the output side of the fan to direct the stream of air to move air in the shop. Sometimes in summer I'll point it at wherever I'm working. The output is so strong that it can readily start an oscillation with the lights if misdirected.

[Alan Schaffter]

A few things everyone needs to realize about ambient air cleaners with HEPA filters:

1) True HEPA filters are very special filters, whose filtering action is slightly different than other traditional organic media filters that work like a sieve (HEPA work on Interception, Impaction, and Diffusion.) Unfortunately that means that while they stop they also entrap fine dust, and contrary to common myth, TRUE HEPA filters are not normally designed to be cleaned and re-used, you can only do that with a few very expensive ones. As a result, they have a limited useful life, especially in an application like a woodworking shop where the dust densities can be very high compared to typical HEPA applications (biological, medical/surgical/operating room, pharmaceutical, electronic fabrication, etc.).

"A HEPA air purifier is not necessarily washable. HEPA filters are made out of loosely and randomly interlaced fibers that are not built to stand up to any stress beyond that of a vacuum cleaner. Washing a HEPA filter will destroy it in most cases."

2) Most HEPA filters are limited in the CFM and air velocity they can handle adequately and without damage.

3) Because of both the media design and the fact that they trap almost all dust, as they collect the dust the CFM drops. The ability to pass free air begins much lower than standard filters and gets worse. SP starts much higher and CFM starts much lower than standard filters and both rapidly get worse- it will take much longer to filter the air in your shop.

[Ole Anderson]

I can't find the airflow data for the Honeywell unit. That makes me nervous. I have a Rockler DustRite (no longer made) with a filter bag and a pre filter. Similar to the popular Jet unit. I have never cleaned the bag just the prefilter, so it is well loaded, therefore better filtration, yet I get plenty of flow. I don't have a particle counter, but seems to work fine for me in my 350 sf shop. But with my DC system, the air never gets so bad you can see any dust in it.

[Mark Furjanic]

The output is really strong and I use the adjustable 90°on the output side of the fan to direct the stream of air to move air in the shop. Sometimes in summer I'll point it at wherever I'm working. The output is so strong that it can readily start an oscillation with the lights if misdirected.

Bill, is there anything holding your unit together or is the weight of the fan all that's needed?
Thanks

[Bill Adamsen]

Bill, is there anything holding your unit together or is the weight of the fan all that's needed?
Thanks

Just weight. Nothing original on my part. Strictly taken from the Bill Pentz web-site (link posted earlier in thread).

[Mark Furjanic]

Just weight. Nothing original on my part. Strictly taken from the Bill Pentz web-site (link posted earlier in thread).

Thank You. I went to Bill's site yesterday when I saw your link and I like the portability along with the better filter. I'll be ordering the parts today.

[Mike Dowell]

Thank You. I went to Bill's site yesterday when I saw your link and I like the portability along with the better filter. I'll be ordering the parts today.

+1 for me. I think I'm going to just go with that. By the way, who the heck is Bill Petnz? And how did he become the de facto air cleaner guru?

[Dean S Walker]

Bill, that is an awesome timber frame shop!

[terry mccammon]

Van,

I don't see a noise rating on the Honeywell site, do you have a sense of how loud this unit is?

Thanks

[Jim Andrew]

When you are hand sanding, you have your nose pointed right at your work. A N95 dust mask will do a better job of protecting your lungs than an ambient air cleaner.

[Alan Schaffter]

When you are hand sanding, you have your nose pointed right at your work. A N95 dust mask will do a better job of protecting your lungs than an ambient air cleaner.

If you have any sort of lung issues this is probably the best way to go- by far!

Another comment about ambient air cleaners. Bill Pentz's unit is certainly one way to go with off-the-shelf parts, though it is pretty darn expensive if built with a Wynn 9L300NANO filter cartridge (my choice for its 300 sq. ft. of filter area), at $178, and a cheap axial, duct fan (like the iPower GLFANXINLINE8, 8-Inch, 745 CFM unit), $85 from Amazon. Similar fans by Fantech, a more reputable manufacturer, run over $400 at Amazon for an 8" unit.

Remember, the effects are similar to what happens in a DC, but even more extreme (one of the reasons why you can't use a furnace fan in a DC) since the fan curve is a lot flatter- it doesn't take much SP (resistance), i.e. adding the filter, to kill CFM quickly- you will not be seeing anything close to 745 CFM (which was likely measured at the outlet/inlet with no duct nor filter.) Bill didn't give any numbers, but maybe someone who has made one of these can take some velocity measurements, calculate CFM, and post the results.

When mated to a filter, if it moves a more-than-generous 250 CFM (just a WAG, but probably not likely), it will take nearly 5 minutes to filter all the air in a modest-sized 12' X 12' X 8' shop, assuming all the air actually gets cycled through the filter (which it won't).

Then, again, depending on the unit's true CFM, it may give you better filtration and CFM at an equivalent or better price than the typical shop air cleaner clones (JET, JDS, Powermatic, Grizzly, Rikon, etc.).

Final note: You just might want to be careful, depending on your state of residence, when ordering one of those fans. From what I could tell by reading the Amazon Q & A, these fans (with charcoal filters) are popular with folks who grow "special plants" indoors in states other than Colorado, etc. wink, wink! Uncle Sam might be watching!