You have probably heard that it’s important to change the air filter in your furnace, but what everyone wants to know is how often it needs to be swapped out and what kind of filters are best.
Many homes use the classic 1″ thick paper pleated air filter, which needs to be changed every 3-4 months, depending on how you operate your heating or cooling system. Even the 2” or 4” thick pleated air filters need to be changed that often, and you should make sure to check the filters more often if you have pets or excessive dust in the home, since these things may cause the filter to get dirty faster.
While most systems are designed to house the filter rack in the furnace or air handler itself, some can be found in the return air grille , which pulls air from the house back to the furnace. You will know it is the return air because the grille is larger than the ones that supply the air to each of the rooms. One side of the grille will have hinges, so you simply swing the other end out to access and change filters.
What I do want to caution you on is not to have a filter in the furnace and in the return air. You will restrict airflow significantly and your furnace will overheat or have to work too hard, causing it to have breakdowns and reduce its life expectancy. It would be like asking you to breathe through a mask 24/7– it would be tiring and would affect how you functioned. Be kind to your furnace and choose only one location for the filter.