How often does the HEPA filter need to be replaced in an air purifier which is running 24/7 and is never turned off?
- spacemissingLv 72 months agoFavorite Answer
Unfortunately there is no perfect answer
because the amount of stuff a filter collects varies from hour to hour, day to day. and week to week.
The most reliable, if terribly vague, answer is "When it becomes sufficiently clogged that it excessively restricts air flow."