The air filter in your HVAC system is perhaps its most important component. While it is easy and inexpensive to replace, the air filter is the first line of defense in preventing breakdowns, maintaining performance and energy efficiency, extending the life of your equipment and protecting your indoor air quality. In other words, a clean air filter is a highly cost effective part of your HVAC maintenance.
How often should you replace the air filter?
Several factors impact how quickly your air filter will clog with dirt and contaminants.
In general, experts recommend a simple rule of thumb for changing your air filter based on the size:
- Change 1- to 2-inch filters every three months. (Scheduling filter replacements with the start of each new season is an easy way to remember.)
- Change 4-inch filters every six months (summer and winter).
- Change 5-inch filters once a year.
In addition to those guidelines, consider the specific conditions of your home. A number of situations could increase the frequency with which you will need to replace your filters. One- to two-inch filters may increase to every month, 4-inch filters to every two months and 5-inch filters to every six months.
Some factors to consider are:
- Home size
The larger the home, the more air that circulates and the more particles that collect in the filter. Therefore, the air filter in a large home may need to be changed more frequently.
- Open windows and doors
Opening windows and doors, while a good way to circulate fresh air on occasion, does allow dust and contaminants to enter your home from outside. If you leave them open regularly, you will likely need to replace your filters more often.
Furry animals, particularly those that shed, will cause your air filter to clog much more quickly. If you have multiple pets, that may increase the frequency to even greater than what is stated above.
The contaminants released from smoking also impact your air filter. The more smokers in the home, the more often you should change your air filter.
- Heater fan
If your heater fan runs constantly, replace your filter once a month; if it runs occasionally, every two months. If it rarely turns on, every three months.
Excess dust can occur from open windows and doors, pets, and other sources. Changing the filter as often as necessary can help alleviate dust accumulation.
Frequent filter changes can greatly help those in the home who suffer from allergies or other respiratory illnesses.
Signs that it is time to change your air filter include:
- the filter is visibly dirty with little or no filter material showing
- the furnace or air conditioner have begun to cycle on more frequently
- your home has become dustier
- a burning smell or other unusual odors emanate from the HVAC unit