This question cannot be answered exactly. Depending on how polluted the air is and how long the unit is in operation, it has to be maintained more or less frequently. You can see this quite well in the first filter. You can clean it yourself. So if the air is extremely polluted during round-the-clock operation. I would say that the carbon filter should be replaced after about 2 weeks. The EPA filter between 2 and 4 weeks. You can see the colour of the EPA filter. If it is nice and white, it is OK. If it gets a little greyish, you should replace it.