I purchased two of these air purifiers, they are good for small rooms, 9x9 feet. They seem to do a good job as we have a several cats and I am allergic to dust that collects on the cat hair and dander. I purchased this model as it has a true HEPA filter, an ionizer than has an on and off switch and a similar larger size Holmes purifier did very well in the Consumer Reports reviews. (CU did not review this specific model. Many other brands did very poorly on the CU tests.) I have had it for a month, it seems to work well. My allergy is better now. (Also have been vacuuming more often with definitely helps.) Overall, I am happy and ordered two more for my other rooms - I think it is better to have two small ones as opposed to one large one, the large ones are noisy and sound like a jet is taxing in your living room. The HEPA filters are $30 for two and they last for year or so. Definitely worth the extra cost to go with the true HEPA filters to get the deep micro cleaning they do - if you go with a cheap washable filter, you are not getting the same benefit. The purifier has three speed settings, I run them at high during the day and medium or low at night - I think the high speed does the deepest cleaning. Medium and low are not very noisy and can be used while sleeping, high seems a little loud for sleeping. It would be nice if they had timers, I may buy some wall socket timers - I think running them on high during the day would be fine. They are made to be ran continuously so you dont need to worry about them wearing out. It has a five year warranty too.