The house we live in has an old electronic air cleaner attached to the furnance. It's a Honeywell F50E 1182. We have lots of wildfire smoke in the PNW right now and am wondering if using this system or putting a regular pleated insert in like they do in this video would be better at filtering out wildfire smoke. I have a 20x20x4 filter I could put in if so.

3 Answers 3


The electrostatic filter will be your best option to filter the smoke, you may need to clean it every week until things clear up, putting a filter that has a finer particulate rating than your system is designed for can cause problems. Your best bet now is to turn the fan on all the time so your air is getting constantly cycled over the grid. If you haven’t cleaned the filter hose it down now so it will be functioning at its peak performance. I have a granddaughter that has serious as a problems and the electrostatic on the furnace keeps the air inside clean enough she doesn’t end up in the hospital. The last time I also closed down the make up air intake as to reduce the amount of fresh air because of the smoke load. With the electrostatic you don’t want to slow the air exchanges these filters when clean are more effective at reducing smoke. A high density filter reduces the air exchanges so it is not as good even if it could take out the finer particles.


Smoke particles are on the order of 1 micron. A "pleated" filter is good down to about 3-5 microns so NO, that will not filter out the smoke. Some will get through.

What you need is a HEPA filter, which usually involves adding a HEPA filter unit into your system and these are effective down to about 0.3 microns.

  • I'm not necessarily looking for something to filter each and every smoke particle out. Just wondering if the filter I have (which is an MPR 1550, MERV rating ~12) is better or worse than the electronic air filter already in place. The 1550 is supposedly rated for 'smoke' on this chart (filtrete.com/3M/en_US/filtrete/about-us/…), but interestingly not for PM2.5, which I believe wildfire smoke is mostly comprised of. In any case, I'm looking for relative performance. In no way can I get a HEPA system installed before tomorrow.
    – gammapoint
    Sep 8, 2020 at 17:52
  • 1
    The PM2.5 filter may help some but as I read the spec for the 1550, it's designed for a 2.5 micro particle size. Unfortunately the smoke particles that travel the longest distances are the smallest ones and I believe you'll find the 1550 filter to be of limited usefulness.
    – jwh20
    Sep 8, 2020 at 18:27
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    I agree it might help but due to the increased back pressure there will be less air filtered and some furnaces will shutdown because of low flow.
    – Ed Beal
    Sep 9, 2020 at 1:59

Need to look at charcoal 'after filters'...Pre filters are the metal grate looking filter that is in there...There is a spot for a after filter...That's what our manual says

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