Effective, White Noise, Blue Light
My brother has allergies and has had problems at our house before; we plugged this in his room and not only did he have no problems, he slept like a log.  The unit gives off a slight white noise; it also has a blue light that is a little too much for me but can be blocked, I guess.  We are very happy with this in an old house that has had some mold and pet hair issues.
Rating: 5 stars