Very effective and quiet.
I can say I'm very pleased at the way it performs. Starting, it takes you through it's four colours and settles generally on blue. It is sensitive to light. At night it goes into a twilight mode... slow and very quiet and reverts to blue when you open the curtains or put the light on.
Most importantly, it is good at it's job. I mainly use it in my bedroom and I used to regularly cough at night but that has reduced considerably since using it .. only 2 weeks.
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