Vicks Pure Warm Mist Humidifier for Relief of Cold & Flu Symptoms. This humidifier boils water to a pure steam vapor up to 96% bacteria free. This mixes with dry air in the cooling chamber to release warm, moist air into the room. Perfect for medium to large rooms. Fill the Water Tank with clean, cool, tap water and replace the Tank Cap by firmly turning clockwise. Turn the tank upright and check Tank Cap for leaks. If any water drips from Tank Cap, remove it and re-tighten.