can you combine a regular return filter if you have a electrostatic hvac filter system as the house? we moved into a house that has this system but my kids have allergies and i understand that the electrostatic filters are not great if you have allergies.

  • Are you asking if you can install a "regular" paper-type filter (of whatever quality necessary) in addition to the electrostatic filter? You can, so long as you have some place(s) to put it, but it will impact air flow. I'll leave it to the HVAC guys to detail what impact that may have on the overall workings of the system.
    – FreeMan
    Commented Apr 16, 2021 at 13:08
  • I have heard from some specialist that electrostatic filter is not good for heals. It emmits some ions. Especially if it affect your child health is better to replace it. Regular filter will not stop the ions. It is just for dust.
    – user263983
    Commented Apr 16, 2021 at 13:24
  • I added regular filters to the return vents, just worried that it will reduce the airflow too much and create an issue with the system.
    – user134005
    Commented Apr 16, 2021 at 13:27
  • @user263983 a electrostatic system can emit ozone but a properly set up system will not have excess ozone / health hazards there is a balance. We could take everything out of the air with electrostatic but then a large amount of ozone would be generated. Pre filtering the large particles reduces the needed strength of the electrostatic field required to capture the particles also keeping the plates cleaner for longer. So a properly sized electrostatic won’t have excessive generation that could be harmful but needs pre filters to block the larger particles.
    – Ed Beal
    Commented Apr 16, 2021 at 14:50

2 Answers 2


Yes standard fiber filters can be added, I suggest adding them at the return point if possible this keeps the heavy dust particles out of the duct system. Having a granddaughter that has severe breathing problems I can tell you keeping the electrostatic filter clean is your best bet. Adding fiber filters for large dust particles is the next best thing.

Adding filters that are very fine are actually counter productive as they slow the air down and reduce the exchanges through the filter system. Also systems are designed for a flow and excessive obstruction can cause shorter system life and even trigger safety components causing the furnace to shut down or cooling system to ice up.

The last few times where my area was choked with smoke from Forrest fires my grand daughter was not hospitalized as has happened in the past.

The electrostatic elements did need to be cleaned at 2 weeks where it is normally a monthly thing and there are the cheap fiberglass filters at the entrance(s) to the system plus the electrostatic.


past 4 years I have been using a washable electrostatic and a $2 washable 3/16" poly foam sheet additionally on top as a pre-filter... (just because), But I like to just pull the pre off more often and do a quick vacuum off/return in between the times I clean the 1" main electrostatic. Using both I have negligible air flow loss. There's also various MERV rated material (cut to size) you can use as a pre-filter if you want a specific rating... but the higher you go the lower the flow and more work for the fan.

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