Filter-free humidifiers are capable of keeping the air humid and clean simultaneously. The device puts moistness back into the atmosphere – as a traditional humidifier – just that it functions without using a filter. While the air stays clean, the device has no removable filters. Instead of removable filters, the machines utilize antibacterial materials, electrostatic charge technology, and pre-heating (for warm mist models) to keep the air cleaned and send it back into the atmosphere in the form of fog.