When it comes to air filter replacement, the general recommendation is to replace MERV 8 filters every 3-4 months, MERV 10 and 11 filters every 6 months, and MERV 16 filters every year. However, if you have fiberglass filters, experts suggest changing them every 30 days. For pleated filters, such as those manufactured by FilterBuy, it is recommended to replace them every 90 days. A rule of thumb for pleated air filters is that a 1-inch filter should be changed every 1-3 months, a 3-4 inch filter should be changed every 6-9 months, and a 5-6 inch coarse-grained filter should be changed every 9-12 months.
This will ensure that your heating and cooling system performs better and that you have clean air to breathe. If you're still unsure about how often to change your air filter, check the packaging for specific recommendations. Additionally, if you are a pet owner, it is best to change your air filter every 2 months. Fiberglass air filters are a low-cost, disposable solution but they need to be changed more often - at least every 30 days.
On the other hand, if replacing the air filter isn't possible for an extended period of time, going beyond 90 days won't cause irreparable damage to your air conditioning system. If there is only a thin layer of dirt where you can still see the filter underneath, then you probably don't have to change the filter. However, if the filter is dirty, it will not be able to filter dust and debris as efficiently and more particles will enter the HVAC system. Additionally, if an air cleaner is not replaced, the appliance will attract more particles from the surrounding air resulting in inefficiency.
Finally, keep in mind that using a filter that is too thick for your system is not good either as it prevents and restricts airflow. Therefore, it is important to get an exact measurement for your oven filter type and make sure that your oven is powerful enough to draw air through higher MERV rated filters.