We love our Germ Guardian (AC4825E). I run it 24/7 it helps cut down a little on the dust, plus we have a dog. There are 5 fan speeds, which also increase in sound, but that isn't a problem for us because it also works as a nice sound mask (i.e. noise cancellation), we have high ceilings and sound travels up to our loft where we keep the air purifier. The filters are easy to replace and when you replace them you will see what the purifier is sucking out of the air, proof that it works. One thing of note, it beeps when the air filter needs replaced and a red light comes on the unit and an error message reading: "replace filter". Once you replace the filter it continues to beep, which is very frustrating, however if you take a pin and push it into the hole under the word HEPA Reset and hold it for a second, it will turn off the beep and you are good to go.

Pros: 1. The machine does a good job of cleaning the air and removing odors. 2. It has a very quiet low speed for night-time use. It’s almost silent, but I have a hearing impairment and those with better hearing may disagree. 3. The device as a separate ionizer and UV-C germ killing lamp. These can be run separately, together, or not at all. 4. There is an automatic shut-off option—user-definable at 2, 4, or 6 hours. The user can also disable the shut-off option. 5. The filters fit nicely into the chassis. This means that the air is properly forced through the filters rather than around the edges. Cons: 1. Panel LED’s cannot be turned off. This turned out to be more annoying than I realized at first. In fairness, the manufacturer clearly indicated that the user could not turn out the lights. While these blue lights do not seem bright in the daytime, they are disturbing in my bedroom at night. Blue light is reportedly disruptive to sleep patterns. I covered the panel for night-time use by using a piece of thin corrugated cardboard. I used thin stock because the switches are sensitive to pressure, and because I could shape the cardboard to fit the curve of the panel. I used duct tape for the “hinges,” and I recommend that you leave a little slack in the tape for this purpose. The photos show how I did this, and also I suggest that you leave an extra quarter-inch of cardboard at the bottom for a “lip” to open the cover. The device does have the ability to turn off the beeping sounds when pressing the switches. At this price point, I would have thought that the manufacturer could also have created an option to turn out the lights or even better, have them time out after a user-selected interval. 2. The consumables are expensive. $75.00 is highway robbery for a filter set replacement every six months or so. Also, the UV-C bulb needs to be replaced annually at $35.00.Three years of consumables cost more than the one-time price of the device, which itself is expensive. 3. The “high” fan speed setting is noisy, even with my hearing impairment. 4. For this price point, the system should include a hand-held remote control. Again in fairness, the vendor clearly indicated that the device lacked this feature.