The WRF – 30 CHC package is for the U-300 device. It includes the pre-filter, 1 Activated Carbon filter, and 1 true HEPA filter. The filters need to be replaced depending on the operating hours of the device and the indoor air pollution levels from gaseous pollutants and particles. An average lifespan for all three filters is one year. These estimates assume the device operates for 12 hours each day and the indoor space has moderate pollution levels.