The life of your carbon filter will depend on how many odors and fumes are in your home. You will be able to tell that you need to replace the F-TN12 when the filter is no longer effective in eliminating the odors. Normally you only have to replace your carbon filter every 4-6 months. Remember that your carbon filter will eventually fill with odors and will need replaced, you can't simply wash the F-TN12.