AHA!! Some data from the Correct Filters’ website. Let’s analyse it!!!
http://www.correctfilters.com/images/uploads/thumbs/thumb_CF_plus_pad.jpgCorrectFilters Plus Pad](http://www.correctfilters.com/filter-refills/correctfilters-plus-pad/prod_3.html)
Product Specifications: Pad Type : CorrectFilters™ Plus (includes 1 year supply) Air Flow : .19 W.G. @ 300 FPM Dust Spot: 22.1% Filter Life: 60 Days Dust Holding: 22.9 grams Efficiency: 92.3% Arrestance INCLUDES: 6 CorrectFilters™ PLUS PADS…
](http://www.correctfilters.com/filter-refills/correctfilters-pleat-pad/prod_7.html)CorrectFilters Pleat Pad](http://www.correctfilters.com/filter-refills/correctfilters-pleat-pad/prod_7.html)
Product Specifications: Pad Type : CorrectFilters™ Pleat (includes 1 year supply) Air Flow : .18 W.G. @ 300 FPM Dust Spot: 35-40% Filter Life: 90 Days Dust Holding: 60 grams Efficiency: 95% Arrestance INCLUDES: 4 CorrectFilters™ PLEAT PADS…
No independently tested MERV numbers and they don’t even show the third of the different accepted tests- the DOP- which is all about the smallest particles which travel deepest into the lungs. Why tell buyers the full story? They may buy someone else’s cheaper filter with better performance!!
Air Flow: [size=3]This is the pressure drop across the filter in inches water gauge when tested with air flowing at 300 feet per minute[/size]
[size=4][FONT=Comic Sans MS][size=4][FONT=Comic Sans MS][size=4]Dust Holding: [size=3]approx 28 grams = 1 ounce[/size][/size][/size][/FONT]
Efficiency (Dust Spot): [size=3]Of the 2 tests mentioned here, this is the one that tells the most. [/size]
Efficiency (Arrestance): [size=3]This is the test used in ads that, IMHO, is a scam used by the filter manufacturers!![/size]
Judging Filters and Air Cleaners
The results of standard tests can help you pick the right filter for your needs. Filter effectiveness is measured by two tests:
Arrestance tends to measure the filter’s ability to remove the largest, heaviest particles. It’s useful only for low-efficiency furnace filters. If you’re concerned about small particles, especially breathable ones, arrestance doesn’t give meaningful results.
Dust Spot Efficiency is a better way to measure removal of fine particles. Use it to compare pleated filters and electronic air cleaners.
Thermal DOP Efficiency applies to the very highest efficiency filters, such as HEPA filters. This is sometimes called “absolute” filtration.
Both arrestance and dust spot efficiency are defined in American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE) Standard 52-89. Unfortunately, some manufacturers list filter “efficiency” or even “ASHRAE efficiency” in their literature, when they mean arrestance. Look for explicit mention of “dust spot efficiency.” Thermal DOP efficiency is tested according to U.S. Military Standard 282. It’s generally applied only to very high efficiency filters, such as the HEPA.
The filter industry divides filters into three groups by dust spot efficiency: Low-efficiency filters are less than 30 percent, with the typical furnace filter below 10 percent. Medium-efficiency are between 30 and 50 percent. High-efficiency are between 50 and 95 percent. “Absolute” filtration is a class by itself where dust spot efficiency is always above 95 percent.
The chart (above) illustrates how the effectiveness of different filters varies depending on particle size. Higher efficiency is usually better, but it can get complicated. Filters with 95 percent arrestance may catch almost all the lint, but few if any of the smaller particles. Many low- and medium-efficiency filters show their lowest efficiency between 0.1 and 0.5 microns. . Two filters perform well across the entire range of particle sizes: HEPA filters and electronic air cleaners.
Note: An analogy about the results of the ARRESTANCE test… It measures total weight of dust collected. If it were a seive for sand and pebbles, but most regular sized sand went through (like small dust particles) only a couple of stones will boost the weight of captured material and give a high percentage captured % (say 95%), making the filter look very efficient when it isn’t. Similarly, catching all the dust bunnies, lint, pet hair but letting most small dust particles go through the filter to be distributed throughout the house is what is happening with the arrestance test!!
For those who want more info: