I have two HEPA Air Purifiers available for pickup in Sausalito. The first is a Whirlpool Whispure AP51030K HEPA Air purifier (the one with single large filter inside) and a Holmes HAP600 HEPA Air Purifier (one with 3 filters inside) available to be picked up. Both units are in good repair and they are working well. I have used the Holmes more and there is evidence of wear and tear on it. However, the unit works without any issues. Both units were rated highly by Consumer Reports Magazine when I bought them. I also have extra HEPA filter cartridges and Carbon filters for both. I have been changing the Holmes HEPA filter cartridges every 12 months and replacing the Carbon pre filters every 6 months. I do clean the carbon pre filters every 2 months.