When the seasons change, and the temperatures dip, you might notice that firing up your furnace also changes indoor air quality. Dry sinuses, itchy skin, and chapped lips are all signs that the relative humidity has declined, and it may be time to add moisture to your home’s air. 

There are numerous ways to add more indoor humidity, from simple DIY techniques to whole-house units integrated into the ductwork and professionally installed near your furnace. 

If you’re not ready to invest in a whole-house system, a portable humidifier designed for smaller areas can provide an excellent, affordable solution in the rooms where you spend the most time. 

But how do you pick the best personal humidifier? There are a dizzying array of options, and manufacturers’ product descriptions often include confusing jargon. To keep things simple, remember that humidifiers generally fall into three broad categories:

1. Cool Mist - Ultrasonic

Ultrasonic humidifiers turn water into a fine, visible mist by vibrating a small ceramic or metal plate (often called a diaphragm or a nebulizer) at an extremely high speed. The vibrations break the water into tiny droplets that automatically rise from the tank. No fan is needed, and very little energy is used!

The primary drawbacks of ultrasonic systems are that they must be cleaned to prevent bacterial or mold contamination, and they tend to cost more than other types of humidifiers. 

Additionally, the cool mist includes fine white mineral dust that will accumulate on the surfaces in your room(s). However, using distilled or filtered water instead of tap water can minimize this problem.

2. Cool Mist - Evaporative

Evaporative humidifiers also use cool water, and they’ve been around much longer than ultrasonic units. 

Aptly named, an evaporative humidifier speeds up the natural evaporation process. A wicking filter is positioned inside the tank, absorbing water from the reservoir. Then, a built-in fan blows air across the moist filter, so tiny water droplets are propelled into the room.

One of the chief advantages of evaporative humidifiers is that they use the least energy. However, their built-in fans can make more noise than other units. They also produce mineral dust and must be cleaned to prevent bacteria or mold growth. 

Even though evaporative units tend to cost less than ultrasonic humidifiers, owners need to factor in the cost of replacing the wick periodically, typically once a year.

3. Warm Mist

Also called vaporizers, a warm mist humidifier relies on boiling water to release steam into the air. However, boiling water is an energy-intensive process, and operating this type of humidifier will be more expensive than cool-mist systems. Also, if the hot water spills, it can burn skin, making this a bad option for households with young children or curious pets.

On the plus side, warm mist humidifiers work silently, are inexpensive, and are easy to find. They are less likely to produce bacteria or mold spores since the water is boiled before it’s released into the air. However, mineral deposits will collect in the bottom of the water tank and must be cleaned periodically.

Finally, some humidifiers offer both cool and warm mist features. When shopping for a unit, you’ll also want to consider how much moisture output you’ll need for your room’s size and the ease of refilling and cleaning the unit.