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Indoor air quality is one of the four pillars of our green philosophy. Besides working with products that don’t off gas things like formaldehyde, filters are high on the list of things we have control over that keeps our indoor air quality in good shape.
Residential air filters are graded on a MERV Scale (Minimum Efficiency Reporting Value) to determine how much the filter media will let pass through. Filters that pull dust and particles from the air are measured in .3 microns to 10 microns. For perspective a human hair is 100 microns. The MERV scale goes from 1-16 with 16 being the highest. A typical residential filter is between 1-4 MERV but superior ones are in the 8-12 range. The one I use is a MERV 8 and is 4″ a pleated paper like media filter. There are other rating systems out there for filtration, but this ones seems easiest to understand and generally acceptable universally.
The thickness of the filter allows for more surface area of filtering media. The 1″ flat MERV 2 will only pull big chunks of dust from the home and where the 4″ MERV 8 will pull dust mites and spores and fine powders like pudding dust.
HEPA filters are designed to remove 97.97% of particles at .3 microns. This would be equivalent to a MERV 20. They filter in a unique way and work quite well. In fact many home vacuums now come equipped with HEPA filtration. Truly a good way to go.
How you use your filter makes a difference too, I leave my fan on year round so in my experience switching filters on a 6 month schedule is perfect. You will want to do filter changes more frequently depending on the way your filters fill up.
Regardless of when you change the filters and how often, having a milestone to schedule filter changes will keep your overall furnace / AC system working properly. Mine is when we switch from Heat to Air conditioning.
We are at the end of April here in Boise Idaho, I often say we are at the edge of the desert but this year we might as well be at the edge of a rain forest. I saw a big show of plum and pear blossoms, and the days have gotten longer, spring has not produced the transition into the cooling season here in Boise Idaho.