When it comes to air filters, the typical recommendation is to change them every 30 days for cheaper fiberglass filters, which don't filter as well. However, it's important to check your air filter at least once a month to see how dirty it is getting. This way, you can compare a clean filter to one that needs to be changed. In general, it's recommended to replace residential air filters every 30 days when using regular fiberglass filters.
When air filters are not changed regularly, dust, pollen, dirt and other contaminants accumulate and reduce the filter's efficiency.