Review on 🌬️ Whirlpool 8171434K Air Purifier Active Carbon Pre-Filters - 4-Pack (Large) - Fit AP51030K, AP45030K, APR45130L, WP500 - 18x16.5 inch by Bill Garczynski

Brief background: I'm a doctor, live in a heavily polluted city, I've been studying the effects of industrial and road pollution since 1995, testing various air purifiers and filters and air quality monitors, have most of my BUYED equipment from Revain and published several websites about air pollution. I am very sensitive to air pollution and usually see spikes a few minutes before good sensors see them. Activated carbon filters are thicker than original filters. They work like a charcoal pre-filter, meaning they clog easily so depending on usage you may need to vacuum them often to fully protect the HEPA filter. I would say once a week but it depends on how dirty the filter is. Filters are fine. The problem lies in the design of the air purifier. TIP: You can wash them and put them in the sun for 1 hour to reuse them. I've only tried it once and it worked. Sunlight has ultraviolet light that ionizes pollutants and removes them from the filter. I recommend rinsing the activated carbon filter first and then laying it out in the sun.