Humidifiers use a range of mechanisms to force extra moisture into the air, increasing its humidity.
An evaporative humidifier employs a fan to run air through a damp filter soaked in a reservoir of water. As the dry air passes through, some of the water evaporates, adding moisture to the air. A steam humidifier, meanwhile, boils water, releasing hot steam.
Finally, inside an ultrasonic humidifier, a diaphragm vibrating at ultrasonic frequencies converts liquid water into tiny droplets, producing a cool mist. Using a humidifier can reduce the symptoms of respiratory conditions or dry skin.