Most air filter manufacturers and HVAC companies recommend changing the air filter every 90 days or 3 months. This may vary depending on the location of your home, if you have pets, and the age of your system and equipment. It is important to check air filters and oven filters at least once a month. If they are dirty, they should be replaced with a clean and fresh air filter.
To determine if the filter needs to be changed, hold it up to a light source; if you can't see the light through the filter, it's time to replace it. Generally, pleated air filters should be changed every 90 days. As the filter traps more dirt, dust and allergens from the air, its efficiency decreases. When deciding when to change an old filter, there are certain factors to consider. The best way to know how often the air filter should be changed is to do a visual inspection of the filter each month.
After a few months, you will get an idea of how quickly it gets dirty. You may need to re-evaluate if you have a new pet or if the outdoor air quality has been poor. Denser filters have a better MERV rating and last longer. Changing air filters is a quick and painless process that can be done in less than an hour. Typical recommendations range from every 30 days for cheaper glass fiber filters (which often don't do a good job of filtering), up to 6 months for high-end pleated filters.
If you use your HVAC system almost constantly, the filter will have to be changed every few weeks (especially if you use fiberglass filters). The type of furnace filter installed will determine how often this task should be performed. If you live in a “smaller house”, your air conditioners and furnaces must pump less air for the same amount of temperature change, which could mean fewer filter changes. The filters are designed to trap dust and airborne particles as the air passes through the filter into the furnace system. You will find it easier to remember to do this important task if you learn how often you should change your air filter in the first place. Households with a pet should generally replace filters after two months; those with more than one pet may need to replace the filter once a month.
Even if no one in the household is allergic, it is advisable to change the oven filter frequently, every 30 days if you have several pets, so that the oven works efficiently. Filters receive a minimum efficiency report value (MERV), which ranges from 1 to 16, although ratings of 6 to 12 are best for residential furnaces. However, if your HVAC system works almost consistently, change the filter every few weeks (especially if you use a cheaper fiberglass filter).
