I have severe dust allergies. I keep a very clean home, however my apartment building was built in the early 1940’s, and even with the remodeling that was done, the vents have never been cleaned. Before owning the Alen air purifier, within an hour in my apartment, I would be sneezing, coughing, runny nose and headaches. Two nights of sleep left me with a respiratory infection that lasted a week. In addition to requesting the building maintenance clean the vents, I purchased this filter and haven’t experienced any symptoms since then. It has completely changed my life. Thank you!