When it comes to air filters, size matters. A three- to four-inch filter can last six to nine months, while a five- to six-inch coarse-grained filter can last nine to twelve months. By changing your filters when needed, you can ensure that your heating and cooling system performs at its best and that you have clean air that's easy to breathe. For 3- and 4-inch filters, plan to replace them approximately every six to nine months.
If you have several pets, you may need to change the oven filter every 30 days, even if no one in the house is allergic. The oven owner's manual will specify the best MERV rating for your oven and, in general, filters with a MERV rating of 6 to 9 should be changed every 90 days, while those with a MERV rating of 10 to 12 should be changed every 60 days. Estimating how often an air filter should be changed can be complicated due to the many variables involved. All air that circulates through the air conditioning system will eventually pass through the air filter.
It's important to make sure that this task is a priority, as changing the filter more frequently ensures that it has enough surface area to filter out contaminants that cause symptoms among loved ones. If you hold the filter close to a light source, you'll be able to see if it's dirty or clogged; if you can't see the light through the filter, it's time to replace it. If you have poor outdoor air quality or pets indoors, you'll need to change your air filter more often. Meanwhile, the use of a 5-inch MERV 13 air filter has a larger surface area and higher dust holding capacity.
However, if you have a smaller appliance used to cool a small space, you may have to change the filter more often than in a larger house. If someone in your household has allergies, more frequent air filter changes are beneficial. No two houses are the same, so despite guidelines, you may have to change your boiler filter more often than your neighbor.