New shop air cleaner.

[Scott Winners]

To be clear I am in a single car attached garage, doing hand tool work indoors. My mitersaw, jointer, planer, circular saw, all outdoor tools - on the driveway pad with the overhead door closed.

This is the air cleaner that works for me on the 85/15 rule, that is I am likely getting 85% of possible results with 15% of effort required to get 100% results:

20231111_143147.jpg

I don't typically mark up for carcass saw cuts with a sharpie, but the line does show in the picture. The idea is the big sawdust particles will fall directly into the trashcan. With the fan on the floor in the background drawing through the (MERV13) furnace filter, the finer sawdust particles should get onto the filter fairly quickly. It does work pretty well, measured air quality in the shop and attached apartment is typically excellent, 0-1 mcg/m3 of PM2.5. The really little stuff Alan Lightstone focuses on, PM0.3 I think, I typically see 200-400 particles per 0.1 liters, and the count will often get down to zero when I have been at my day job instead of playing in my shop for a couple days.

However, I do sometimes need to make a bigger mess than crosscutting a furring strip.

[Scott Winners]

The new thing is overkill for my small shop. I built it as a whole house air cleaner for summertime wildfire season. The airhandler in this space has a pretty good prefilter on it, when outdoor is up to 50mcg/m3 I get essentially zero particles into the space. 50 mcg/m3 is getting way up the "unhealthy for sensitive groups" are and getting pretty close to "unhealthy." In summertime wildfire season it is not unusual for me to have legit hazardous airquality on the back lawn, literally 300-400 mcg/m3.

I'm in about 900sqft with ten foot ceilings, so about 9k cuft, this should be plenty.

[Scott Winners]

Construction is strictly WYSIWYG. This one is my second build at this size.

The first one had 3 inch casters under it, which sucked. I also had to wrap duct tape around the top and bottom edges when installing filters. Duct tape will fold around an edge, but it is a pain in the neck. For this new one I used four inch casters with urethane tires, and there is about 20 pounds of unspecified sporting goods in the green box in the floor of the filter. For the first one I had used a cinderblock thing, nominal 2x8x16. I have heard them called patio block and also cap block - that thing made out of cinderblock material. I think it was enug ballast, but the casters were definitely too small.

Motivation is by a 20" box fan resting on weather stripping. I will have some observations about the "new" Lasko box fan I bought at a home store recently in a future post.

The section or module for this design ended up being 5 inches. The 4" casters once mounted lift the case bottom 5" off the floor. The top and bottom plywood bands are 5" tall. The top surface of the fan sits pretty close to 5" above the top of the case, and the furring strip boxing in the fan is 2.5 inches wide. Blade width between elements is 1.5 inches, from nominal 1x2 furring strip. The middle band of plywood is 1 module plus one blade, so 6.5 inches tall. I am very pleased with the vertical proportions in general, enough so that the assymetric horizontal width of the vertical corners kinda bugs me a little bit, but it is ultimately shop furniture and it will be fine.

Once this new filter was fully assembled I was able to sweep up and vacuum and put away all the things. With just the one filter taped to the back of the fan n the floor I had donuts for particles in the shop space, but had built up some CO2 since the shop space has filtered circulation, but no ventilation with the door to the apartment closed. That is a different problem.

[Scott Winners]

Since I didn't have any particles to worry about, I opened the door between the shop and the living space, manually turned on the air handler and ran some errands. I came home to CO2 levels around 350ppm, pretty close to outdoor ambient.

I shut the shop door, turned the new big filter unit to high speed and (long overdue) flattened my benchtop. Once that was done I built a new clamp so I can sharpen backsaws in my leg vise - and ran the CO2 up over 1100ppm this time, but no particles. I do need a better ventilation strategy for my workspace.

[Scott Winners]

Be forewarned the new style Lasko fan has a physically larger case than the last style that I really liked. I am already cruising CL and marketplace for the older style I have had good results from. I carefully chose a shipping box with no visible damage, but had to repair a broken weld on my new unit anyway.

Good luck and best wishes. MERV 13 forever.

[Steven O Smith]

I use the FPR10 filters from Home Depot. They claim the FPR10 compares to MERV13, it's kind of a squishy comparison. Goes together very quickly, looks like Scott's larger Lasko fans will be a problem (I'm using 20x20 filters). The fan air flow goes up.
I'm using four filters to reduce the load on the fan motor. For details, search for Corsi-Rosenthal Box.

air_cleaner.jpg

Steve

[Scott Winners]

I use the FPR10 filters from Home Depot.

Steve

Yup, last time I looked the team orange home store "team orange level 10" furnace filters met spec to be considered MERV13. There is a fairly good comparison table behind this link: https://www.epa.gov/indoor-air-quali...at-merv-rating

My local team orange doesn't carry level 10, and my other local retailers don't carry 3M Filtrete 1900 or 3M Filtrete 2200, so I pretty much have to buy online to bring in MERV 13.

Besides Corsi-Rosenthal box, folks can also search on "Comparetto cube." I have been at this for a few years now and have yet to find any online drama between Corsi and Comparetto and Rosenthal. As near as I can tell all three want each of us to have the best indoor air quality possible, and here are some free ideas to try.

I haven't invented anything, I have just been tweaking at stuff those three thought of.

My wife does have a pretty severe mold allergy. I have found (not published) MERV 13 filters do a better job at trapping really small particles at lower air velocities. By spreading around 6 filters (in parallel) in one cabinet, only 1/6 of the cfm the fan is drawing (nominal) is coming through each of the 6 filters, so I get (my one data point) better capture of particles under 2.5 microns. Certainly if I stacked 6 filters in series with some duct tape so the fan was drawing through a single 20x20 inch inlet _and_ 6 MERV13 filters I would be putting a heck of a lot of load on the fan.

Per the table above, MERV 13 gives me 85% capture rate on PM2.5 each pass. So if I have hazardous (wildfire season) air quality at 400 mcg/m3 of PM2.5 in the front yard, I can capture 85% of those particles first pass, so my indoor air quality should be closer to 60 mcg/m3, still "unhealthy" but the cutoff to get down to "unhealthy for sensitive groups" is 55 mcg/m3. From "60" I should have no problem getting down to under "35" second pass, which will put my indoor air quality into the moderate area. As long as the cfm through the pictured filter unit is double the cfm through the household air handler, I should have moderate air quality indoors when outdoor air quality is hazardous - with PM2.5 as the controlling variable for air quality.

In our new very tightly constructed space, CO2 is often the controlling variable for determining indoor air quality. Under 700ppm is the green zone, no intervention required. 700-800 ppm is one yellow flag. 800-1000 ppm is two yellow flags. Greater than 1000 ppm is the red zone wherein active intervention is strongly advised. Our new place is so tightly built that when I close any of the man doors I can hear the flapper plates on the clothes dryer vent rattle. Our energy bills for heating are remarkably low, but I do have to ventilate the space to control CO2.

My new Lasko fan is something like 1/2 to 5/8 inch bigger horizontal and vertical compared to the old style. I already had 3 of my 4 sideboards glued in when I bought a new Lasko at the home store- so I put the old one on the cabinet and taped a new filter onto the back of the new Lasko and stuck the new one on the floor. I don't prefer the Utilitechs. They are louder than the old Laskos out of the box, and the Utilitechs get louder and louder. I think my oldest old style Lasko is pushing 5 years old, continuous duty on low (24/7/365) pulling through 3 of 20x20 MERV 13 filters and it is still quieter than a new Utilitech.

Given the supply chain and the realities of manufacturing, for a new build it might make sense to just cut a 20" diameter round hole in the top of a new build cabinet, lay down a round layer of weather stripping and then use duct tape to attach the fan to the top of the cabinet. This will insulate the builder from future design specification changes.

I will require (at best) 5 years to render an informed opinion about the new style Lasko compared to old style, but my enthusiasm is, and expectations are, pragmatically limited.

[Scott Winners]

I use the FPR10 filters from Home Depot.

Steve

Yup, last time I looked the team orange home store "team orange level 10" furnace filters met spec to be considered MERV13. There is a fairly good comparison table behind this link: https://www.epa.gov/indoor-air-quali...at-merv-rating

My local team orange doesn't carry level 10, and my other local retailers don't carry 3M Filtrete 1900 or 3M Filtrete 2200, so I pretty much have to buy online to bring in MERV 13.

Besides Corsi-Rosenthal box, folks can also search on "Comparetto cube." I have been at this for a few years now and have yet to find any online drama between Corsi and Comparetto and Rosenthal. As near as I can tell all three want each of us to have the best indoor air quality possible, and here are some free ideas to try.

I haven't invented anything, I have just been tweaking at stuff those three thought of.

My wife does have a pretty severe mold allergy. I have found (not published) MERV 13 filters do a better job at trapping really small particles at lower air velocities. By spreading around 6 filters (in parallel) in one cabinet, only 1/6 of the cfm the fan is drawing (nominal) is coming through each of the 6 filters, so I get (my one data point) better capture of particles under 2.5 microns. Certainly if I stacked 6 filters in series with some duct tape so the fan was drawing through a single 20x20 inch inlet _and_ 6 MERV13 filters I would be putting a heck of a lot of load on the fan.

Per the table above, MERV 13 gives me 85% capture rate on PM2.5 each pass. So if I have hazardous (wildfire season) air quality at 400 mcg/m3 of PM2.5 in the front yard, I can capture 85% of those particles first pass, so my indoor air quality should be closer to 60 mcg/m3, still "unhealthy" but the cutoff to get down to "unhealthy for sensitive groups" is 55 mcg/m3. From "60" I should have no problem getting down to under "35" second pass, which will put my indoor air quality into the moderate area. As long as the cfm through the pictured filter unit is double the cfm through the household air handler, I should have moderate air quality indoors when outdoor air quality is hazardous - with PM2.5 as the controlling variable for air quality.

In our new very tightly constructed space, CO2 is often the controlling variable for determining indoor air quality. Under 700ppm is the green zone, no intervention required. 700-800 ppm is one yellow flag. 800-1000 ppm is two yellow flags. Greater than 1000 ppm is the red zone wherein active intervention is strongly advised. Our new place is so tightly built that when I close any of the man doors I can hear the flapper plates on the clothes dryer vent rattle. Our energy bills for heating are remarkably low, but I do have to ventilate the space to control CO2.

My new Lasko fan is something like 1/2 to 5/8 inch bigger horizontal and vertical compared to the old style. I already had 3 of my 4 sideboards glued in when I bought a new Lasko at the home store- so I put the old one on the cabinet and taped a new filter onto the back of the new Lasko and stuck the new one on the floor. I don't prefer the Utilitechs. They are louder than the old Laskos out of the box, and the Utilitechs get louder and louder. I think my oldest old style Lasko is pushing 5 years old, continuous duty on low (24/7/365) pulling through 3 of 20x20 MERV 13 filters and it is still quieter than a new Utilitech.

Given the supply chain and the realities of manufacturing, for a new build it might make sense to just cut a 20" diameter round hole in the top of a new build cabinet, lay down a round layer of weather stripping and then use duct tape to attach the fan to the top of the cabinet. This will insulate the builder from future design specification changes.

I will require (at best) 5 years to render an informed opinion about the new style Lasko compared to old style, but my enthusiasm is, and expectations are, pragmatically limited.