In general, most air filters should be changed every 90 days or 3 months. This is the ideal timeframe, however, there are certain factors to consider when determining when to replace an old filter. The basic consensus among HVAC professionals is that you should replace your oven filter every 90 days or every three months. However, this may vary depending on the thickness of the filter.
Thicker filters have more room to pick up dirt and dust, so they don't need to be changed as often. Thomas & Galbraith Heating, Cooling and Plumbing of Ohio recommends replacing filters that are less than 2 inches thick every 30 to 90 days. Three- or 4-inch filters can last 6 to 9 months, and filters up to 6 inches thick can be replaced once a year. A general rule of thumb for pleated air filters (such as those manufactured by FilterBuy) is to replace the filter every 90 days.
As the filter traps more dirt, dust and allergens from the air, its efficiency decreases. If you use less expensive fiberglass filters, it's recommended to change them every 30 days. Furnaces and air conditioners in smaller homes need to pump less air for the same amount of temperature change, which can mean less frequent filter changes. If there is a visible layer of dirt that covers most of the filter surface and that is thick enough to hide the filter material itself, it is a sign that the filter has been in the HVAC system for too long.
A number of factors need to be considered when deciding how often to change an oven filter, and many filter manufacturers recommend how often your product should be replaced. If there is no smoker or pets in your home, and your filter is the 1 filter that is commonly sold with a MERV rating of 4, you should be able to wait up to 90 days before changing it. The HVAC air filter will basically trap airborne contaminants to prevent them from being recirculated throughout the house. Therefore, in addition to causing breakdowns, it can also increase energy bills because the HVAC system has to work overtime.
During a remodeling project, change the oven filter every 30 days, or even more often, to prevent construction-related dust from circulating around the home.