Your furnace filter is an important part of your home's heating system. It's main purpose is to remove particles and debris from the air entering your furnace in order to protect the mechanical components of your furnace, such as the motor. Here are some basic tips to make sure that your filter is doing it's job:
1) Check & change your filter regularly - This is typically every 3 months, but more often if conditions require (ex. if you live in an area with a lot of dust, if you have pets who shed, or if you run your furnace fan continuously).
2) Never try to clean a disposable filter - the materials break down over time and are not meant to be reused or cleaned.
3) If your filter doesn’t fit, it doesn’t filter - Air takes the path of least resistance so it is important that your filter fits in as closely as possible. It needs to reach right to the end of the filter track, and there should not be a visible gap on either the plenum or the furnace side. If your furnace needs a specialty size, you should get one, or, get your filter slot changed to fit a standard size. If there is a gap to the sides of the filter and there is not a snug fitting door, using a piece of duct tape down the slot to seal the gaps is a good idea.
4) More "Merv" is not always better - A good Merv rating for residential use to balance particle trapping with air flow is between 5 and 8. You should consult with an HVAC professional before using a very high Merv filter, as your system may not be able to handle the air drop (decrease in airflow) caused by a very high efficiency filter. If you have a 2” or a 4” filter slot, using a filter with a higher Merv rating will be less of a concern, as the higher surface area of a thicker filter causes less resistance to air.
5) Consider Running Your Furnace Fan Continuously - To encourage continuous air flow and filtration, run your fan continuously. Keep in mind that if you have not done this before, you will need to check your furnace filter more regularly, as running the fan will pull more air through the filter and cause it to become full quicker.