The Essick Air 1970 Humidifier Bacteriostatic Treatment helps to control bacteria and algae growth in evaporative humidifiers. When filling the humidifier, use 1/6 fluid ounce (approx. 1/8 capful) bacteriostatic treatment per gallon of water. Repeat process when refilling. Regular use will eliminate bacteria/algae growth and keep your unit smelling good.