Philips air purifier is good for those with asthma or cats, and suffer from litter box odors or struggle with dust. It has three modes and three colors. Blue means the air in the room is good, purple means there is light dust in the air, while red means the place is very dusty or has a strong odor. It has a filter, but it's best to buy a new filter, especially if you have asthma, just as a precaution. Only serious buyers should contact me.