This is my first air purifier. I bought this unit after reading about it and comparing it to other brands hoping it would reduce the dust in my living room area and help with my allergies. I must say I am very disappointed because I have noticed no difference whatsoever. The fan also throws out cold air which makes the room colder which then kicks on the heat more often which translates to higher electric and heating bills. I wouldn't mind the higher bills if the unit made a difference in reducing dust and helping me to breath better due to my allergies.