The biggest factor in how often you should replace the filter is the type of filter used.
There are two main types of filters to choose from:
Both types are disposable, but there are some important differences.
1 Fiberglass Air Filters
Fiberglass air filters are less expensive than the two but are effective at capturing dust and particles in the air.
They usually need to be replaced every 30 days or less.


2 Pleated air filters.

Pleated air filters are more expensive at first, but they are also more effective at capturing particles and can last up to 90 days, depending on use.


When you purchase a new air filter, you will find the manufacturer's recommended replacement plan.
This is a general guide, depending on the following factors
Home size.
Home size is an important factor in determining the frequency of your filter change. Large homes, for example, pass a lot of circulating air through a furnace or air conditioner. This means that filters may get dirty faster and need to be replaced more frequently. In smaller houses, the HVAC system has less air, which may mean less frequent air filter replacements.

Tip: Homes may also have small appliances, such as air conditioners with smaller air filters. In this case, the filter may need to be changed as often as in a larger home.

Air quality.
The quality of the air outside has a big impact on how often your air filter becomes dirty and needs to be changed. If you live in a large city, pollutants such as smoke, dust and other debris will seep inside and clog your air filter faster. Wildfire smoke also plays a big role in the need for frequent filter changes. After a period of smoky days with poor outdoor air quality, check your air filter to see if it needs to be replaced.