First off this is most likely free to try, as in you probably can do it with stuff you already own and two minutes of time. No purchase necessary but you might want to read the warnings.
I live in an older house, although some newer houses have this also. I was dusting pretty regularly, blowing dust out of my power supply, have a couple of air filters running constantly, and everything always was lightly coated in dust after a month or so, especially the front of my computer and anything remotely electronic (or perhaps I was just seeing it on the black devices.) My air filters also lasted significantly longer than should be expected before needing washed, replaced, etc. and generally I was wondering why there was always so much dust around. Shouldn’t the filters be acting to get the dust out?
Turns out the air filters weren’t doing their jobs. Not because they were bad, nor was there a hole in the duct work, but because air goes the path of least resistance and AC installer had installed two non-sealed air returns. Sad trombone noise.
I talked to my new AC guy who said that an easy way to test whether the air is actually being filtered and removing dust and airborne particles, was to simply grab some painter’s tape and seal around the edges. If you do this while the fan is blowing, by the time you are on your last tape run the tape will probably be being sucked down.
The painter’s tape will create an airtight seal around the edges of the filter forcing the air to actually go through the filter.
In my case on the last side taping the air started whistling on one of my returns, and making farting noises on the other.
Two months in and I no longer am watching dust motes in the morning sunlight, and my dusting routine’s been thrown off as there’s very little dust anymore.
I have washable filters and have had to clean them three times in the last two months as they were caked in dust. I have not had to dust since week four of this experiment. The painter’s tape peels right off and can be reused unless you rip it. I’m at three or four uses now of my original tape runs.
Whole heap of warnings
If you actually do this while the fan is on and screw it up, painter’s tape may go into your intake, hit the fan, and burn down your house. OK, probably not burn down your house but damage the air handler. Don’t drop anything in your air return.
If you’ve been getting heavier and heavier air filters hoping to clean out allergens and suddenly you create a perfect seal, there’s a very good chance your blower will start working overtime to pull air through the heavier filter.
There’s also the chance that your air blower is on its last legs and making it do the work it was originally designed for will push it right over the edge. Try this with some cheap-o light filters first rather than your $20 super hepa filter that looks like it could take a bullet.
If this works you’re going to go through filters pretty fast the first couple of months. I’ve got washable ones, in my case I ended up basically having a mud bath with them, they were caked and filthy at two weeks. Remarkably clean now however.
Forcing your air conditioner’s filtration system to work can cause increased electricity usage as the filter is now actually filtering.
How long does this take to work
Depends. For me in a 1940’s Craftsman-style house I saw layers of dust on my filters at a little over a week and washed them at two weeks (usually had to every six weeks) and four weeks. By month two I didn’t watch dust motes in the morning sunlight, I don’t sneeze, and I don’t have to dust every couple of weeks.
How much does this really cost?
Painters tape can be purchased for about 3 cents a foot. a 24×24 filter seal will run you about 24 cents. a 40×40 filter about 53 cents. I’m at four uses of the tape and probably will get a few more out of it. So in a non-dusty 90-day scenario you’re probably looking at less than a buck a year.
I won’t factor in increased blower electricity usage as it’s now doing what it was supposed to.