Get one or two dehumidifier(s) depending on the size of your room. A 4x4m room needs a 10L/Day dehumidifier (it removes 10L of water in the air per day). Apparently, fleas require 50% or higher relative humidity to live.
Throw all of the pet bedding in the washing machine. This includes anything that the pets like to regularly lie or sleep on which isn't always intended to serve as pet bedding. If the bedding can go in the dryer, 15 or 20 minutes in a hot dryer will kill adults, larvae and eggs.
For more you can refer to this site.