For optimal performance, vacuum, wipe down, or rinse off the prefilter every month or so. The prefilter catches larger particles, such as pet hair, and keeping it clean helps the HEPA filter work unimpeded on fine particles. Although the AC4825 performed well, it costs more to maintain than our current budget pick, the Levoit Core… Continue reading LEVOIT 24db Smell Reducing HEPA Filter Air Purifier