How often to change activated filter carbon depends on the type of filter and how it's used, but here are some general guidelines:
Air filters
A good quality activated carbon air filter typically lasts about six months and should be replaced once a year. However, the quality of the carbon, how often it's used, and other factors can affect how long it lasts.
Water filters
Activated carbon water filters typically last 2–6 months, but can last up to 12 months in some cases. Factors that affect how long they last include the quality of the carbon, how often they're used, the quality of the tap water, and the humidity.
Aquarium filters
A general rule of thumb is to change activated carbon in an aquarium filter once a month. However, the only sure way to tell if it's spent is to measure the water.
If you're unsure how often to change your activated carbon filter, you can consult the manufacturer for guidance.
