Summary: I bought the T100 back in 2008 for my son who has dust allergies. It's worked well, and using a Kill-A-Watt, I found that leaving it on 24/7 on low costs something like $1/month. Last week, the fan got pretty loud, sounded like it was loose or a bearing was shot.
Summary: I purchased one of these for my son's dorm room. He used it for a couple of years. Brought it home and said, "It's making loud noises." I called Alen and they immediately got all my info, told me to throw away the unit, and sent me a brand new one two years later.
Summary: First of all I did not expect any magic out of this device in first place. I bought it to have additional air cleaning in kid's room. I have no objective mechanisms of measuring if it really improves air quality or not.
Summary: I can't give a complete product review because this was a present for my mother who is asthmatic. It got there in great time and so far it's only been a month but she loves it and has said that it's not loud or extremely big.
Summary: I've owned A LOT of air purifiers because I suffer from chronic sinusitis. This unit is simple to operate, seems very well made, is extremely quiet (even on high) and leaves a "fresh" smell in my laundry/utility room. I purchased the optional odor absorbing filters.
Summary: I've been using this air purifier in my room for several years and it's still working fine. It is very quiet at the lowest fan setting. Even at the highest setting, it is not as loud compared to the other air purifiers being sold in the market.
Summary: I have Alen T300. It is whisper quiet unit with good performance. I wanted to buy smaller unit for bedroom and ordered T100 expecting it to be similar to T300. Only similarity between these two units though is design and HEPA filter - T300 uses two TF30 filters and T100 only one.