Real World CFM
Avoid using the manufacturer's cfm numbers when comparing air cleaners. These are often based on the blower running without the filters installed. Not a very realistic number.
We took a total of six cfm readings on each machine, starting with clean filters and once for each 16-gram loading of test dust. As the filter loads with dust, the cfm decreases. The "Dirty Filter CFM"rating in the chart is the last reading taken after all 80 grams of dust have been run through the machine. The "Average CFM" in the chart represents the average of all six readings and is a good working number to use when determining what size machine you need for your shop.
What Size Air Cleaner Do I Need!
As a rule of thumb, your air cleaner should filter all the air in your shop every six minutes. This is a minimum. An air cleaner that can do the job in less time is better because it will clean the contaminated air in your shop that much more quickly. To determine the size or how many cleaners you need, start by calculating the cubic feet of your shop (L x W x H). Divide that number by 6 and you'll have the minimum number of cubic feet per minute, or cfm, the air cleaner needs to pidl through its filters. Use the "Average CFM" number from the chart to see if the collector you're looking at is right for your shop space.
For example, if your shop measures 15 ft. x 20 ft. x 8 ft., it contains 2,400 cubic feet of air. Divide by 6 to get the minimum cfm required, in this case 400.
Air cleaner pre-filters are either disposable or washable (Photo I). The choice is yours. A disposable pre-filter will be replaced many times before the pocket filter behind it needs replacement. You may be tempted to vacuum off a disposable pre-filter, but don't. This can damage the fabric and reduce the filter's efficiency.
Washable pre-filters, on the other hand, offer convenience and long-term cost savings. When they get dirty, you simply rinse them out, let them dry and put them back into service. The money you save using a washable filter may get spent in more frequent pocket filter changes, however, because the washables let more dust through. Remote Control
A remote control may be important if your machine is going to be out of reach (Photo 3). On some machines the remote control is the only way to adjust speed or set the timer (a bad deal if you run out of batteries or lose your remote).
A timer and/or variable speeds are available on some machines (Photo 4). Timers are great and allow the machine to keep cleaning your shop air when you're not there. Variable speeds allow you to run your machine at a lower cfm. This reduces the noise you have to put up with, but the lower cfm also reduces the effectiveness of your cleaner.
These machines are running for long periods of time, so noise can be an issue. All the machines were relatively quiet (we're talking about a woodshop here). The trade-off for a quiet machine is lower cfm. You just can't have your cake and eat it, too.
Our picks represent the optima! combination of cfm and filtration. Units that allowed more than a gram of dust through were excluded from consideration. At first glance, this may seem overly restrictive, but a small difference in efficiency can make a huge difference in effectively capturing small, health-damaging dust particles.
A couple of models would have made Best Buy and Editors' Choice had filtering or cfm performance been better.
The Delta 50-875 was a top Editors' Choice contender. It has great filtration but about 11 - percent less cfm than the Editors' Choice, the JDS 750-ER.
Jet put up some strong cfm numbers, but both Jet machines let more than twice as much dust through as the JDS 750-ER.
The General Int'l 10-550 comes with a remote and good cfm, all at a great price. It would have been a strong Best Buy candidate if it hadn't Set through four times more dust than the Delta AP-200, our Best Buy. The same thing can be said for the Shop Fox; great cfm and good features, but it fell down on filtration. The Lee Valley 03J05.20 took top honors in filtration, but was weak on the cfm side. AW
An air cleaner from Harbor Freight (800-423-2567), model #46361, arrived too late to include in the laboratory testing. At $ 170, it is the lowest priced machine in the group. It's quiet, and includes a radio remote control and hanging hardware. However, the filters are only capable of filtering to 20 microns.
Craftsman and Grizzly declined to participate in this tool test.
Delta AP-200 & Delta 50-875
General Int'l 10-600 MI
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