The life span of your Air Purifier filter depends largely on the air quality in the room it's operating in. The average amount of time that a filter is working at its best ability is 12 months. However, you must take in account the environment that your Air Purifier is in. If your unit is located in a room with heavy smoke, the life span of your WINIX filter will be reduced. All WINIX Air Purifiers are equipped with an automatic filter replacement indicator. The indicator will illuminate when your WINIX Air Purifier filter needs to be replaced.