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. Fiberglass air filters are the more affordable option, but they are less efficient at capturing dust and particles in the air. It is recommended to change them every 30 days or less.
Pleated air filters (such as those manufactured by FilterBuy) should be replaced every 90 days. As the filter traps more dirt, dust and allergens from the air, its efficiency decreases. However, if you purchase an older system, plan to replace the filter more frequently to maintain filter quality. If there is a visible layer of dirt that covers most of the filter surface and that is thick enough to hide the filter material itself, it is a sign that the filter has been in the HVAC system for too long.
At this time, it is recommended that air filters be replaced with quality replacements that can filter out common allergens, including pollen. If you have an asthmatic or allergic person at home, change the filter every 6 weeks to ensure that the indoor air quality is the best. Typical recommendations range from every 30 days for cheaper fiberglass filters (which often don't do a good job of filtering), to 6 months for high-end pleated filters. Some manufacturers recommend replacing air filters every 30 to 60 or 90 days, depending on the type of air filter. More cycles mean more filter passes and opportunities to trap contaminants, so filters typically fill faster during periods of heavy use.
Changing the filter more frequently ensures that the filter has the available surface area needed to filter contaminants that trigger symptoms among your loved ones. The only way to ensure how often you need to change your air filter is to perform a visual inspection of the filter every month. A professional will be able to help you if there is a particular protocol for changing the air filter of a specific brand or how often an air filter needs to be changed. If there is no smoker or pets in your home, and your filter is the 1 filter that is commonly sold with a MERV rating of 4, you should be able to wait up to 90 days before changing it. In addition, not replacing the air filter accordingly can cause the homeowner's energy bill to rise, as clogged filters cause the system to work harder when air circulates.