How can I use an air purifier?

Put it in your bedroom so you have clean air while you sleep. If you have allergies, the clean air will give your body time to heal and make it easier on you the next day than it would be otherwise.  Air purifiers now have the Hepa filters which will catch the allergens. 

Plug it in and turn it on in the room people spend the most time in I suppose. They also usually need to be cleaned regularly to remain effective.