In general, most air filter manufacturers and HVAC companies recommend changing your 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. The only way to determine how often you need to change your air filter is to inspect it visually each month. After a few months, you will get an idea of how quickly it gets dirty and if you need to adjust the frequency of replacement.
Air filters and oven filters should be checked at least once a month. If they are dirty, they should be replaced with a clean one. To check if the filter is dirty or clogged, remove it from the air handler and hold it close to a light source. If you can't see the light through the filter, it's time to change it.
The ideal is to change your air filter every three months, however, there are certain factors to consider when determining when to replace an old filter. A general rule of thumb for pleated air filters (such as those manufactured by FilterBuy) is to replace the filter every 90 days. As the filter traps more dirt, dust and allergens from the air, its efficiency decreases. You should replace the filter more often if you have a new pet or if the outdoor air quality has been poor. During a cold winter or hot and humid summer, you will need to change the filter more frequently than during milder seasons.
Remember that a filter also gets dirty during AC mode. If you find pet hair in your oven filter, it should be replaced more often as hair fibers clog the filter quickly. The more important clean air is, the more often the filter needs to be cleaned or changed. A coarse-media filter, MERV 11 or higher, or an electronic air filter is the best option when someone in the household has asthma, severe allergies, or difficulty breathing for any reason. In larger homes, more air flows through the filter than in smaller houses so it will get dirty more quickly. Some sites suggest that thicker filters can last longer between changes but this goes against their design.
Coarse-media filters trap more and smaller dust particles so they clog up faster than slim fiberglass filters which don't trap as much dirt and debris. Some filters can be cleaned with a nylon brush and placed back in the oven or air controller instead of replacing them but cleaning should be done outside or in a garage to keep dust and dirt out of your home. If removing dirt with a brush instead of replacing the media filter, be sure to change the filter after two or three cleanings. Some people wonder what continuous fan mode is and why a homeowner would use it. There must be a setting in the thermostat such as Auto and Fan options.
In automatic mode, the fan works only when the system is heating or conditioning the air in your home while in fan mode it works all the time until you turn it off. Running the fan requires electricity so you'll see an increase in your electricity bill and humidity makes you uncomfortable in summer so you'll need to lower your thermostat settings to get rid of moisture which is counterproductive causing the air conditioner to work more often. In summary, we do not recommend continuous fan mode as a standard operating procedure as it increases electricity costs without providing any real benefit. The best way to ensure good indoor air quality is to check your air filters at least once a month and replace them when they are dirty or clogged. Pleated air filters should be replaced every 90 days while fiberglass filters require less frequent replacement.
