Humidifier Buying Tips
There are three main types of humidifiers- consider the pros and cons of each when researching your purchase descision:
Cool Mist (Evaporative) Humidifiers
This is the most common humidifier type, and the type most people are familiar with. It uses a wick-type filter that absorbs water, in combination with a fan that blows air through the filter. The air blowing through the filter causes the water absorbed in the filter to evaporate into the room air and thus increase humidity.
Since the water is evaporated, minerals are left to accumulate in the wick filter. This means the moisture released in the air is pure water, but the filter will need to be replaced every few months. Mold and bacteria can also grow on the filter, but this can be treated with a Bacteriostatic Treatment.
Warm Mist Humidifiers
The principal behind a warm mist humidifier is pretty simple- it boils water, creating steam, then lets it cool into a warm mist that's released into the air. Like cool mist humidifiers, mineral deposits in the water are left behind, ensuring the humidity released into the air is pure water vapor. Unlike cool mist humidifiers, no wick filter is needed. Since the mist released is warm, it can help warm a cool room, which can be welcome in the winter months. However, it can create a "muggy" feeling in the air which may be uncomfortable.
This type of humidifier uses high-frequency sound waves to turn water into a fine mist which is blown into the air with a fan. Minerals present in the water are not left behind in this process, so unless the water is distilled, a whitish mineral residue can be left in the vicinity of the humidifier. Some ultrasonic humidifiers use cartridges that are meant to trap minerals before they're released into the air, but they don't always capture all the impurities.