Noticed the difference within a hour and feeling alot better what a life saver this unit is, highly recommend this to anybody who is looking for air purifier for their bedrooms. It does excellent job at cleaning the air including dusts. You would want to keep the fan speed on 1 while you go to sleep as fan speed 2 is abit noisy and fan speed 3 is alot noisy but good to use in the day time. I put fan speed 3 in the day time, and then at night I use fan speed 1.
UPDATED: Running this great little unit 24/7 for the last 3 months and have to say I'm quite surprised how much it collects on the filter which you can see in the photo. HIGHLY RECOMMENDED!!