Pre-Filter: Dust and other large particles will collect on the pre-filter over time. The color of the filter will change as particulates build up on the pre-filter. Change the pre-filter when you can see the particulate buildup start to clog up the pre-filter.
HEPA Filter: As the HEPA filter captures particulates, it will darken over time. Replace the HEPA filter when it darkens to the level seen in the image below.
Inner Carbon Filter: The inner carbon filter will rarely look used. This filter captures odors and gases, yet the filter’s appearance will not change. When this filter has reached its maximum absorbency of odors and gases, it will no longer work. Replace this filter when it no longer seems to capture odors, or every 3 months (12 months for optional Carbon Canister), whichever occurs first.
NOTE: According to the manufacturer, filter life is based on average air content. Some filters may need to be changed more often due to higher amounts of dust, humidity, or chemicals found in your ambient air. Additionally, people who are more sensitive to these airborne contaminates may desire more frequent filter changes.