What the best humidifier has
- Simple maintenance. According to the Mayo Clinic, humidifier tanks can become a breeding ground for bacteria or mold if not kept clean, in turn aggravating allergies and respiratory problems. Look for a humidifier whose parts are easy to disassemble and clean.
- Low noise. In general, ultrasonic humidifiers are quieter than evaporative ones, which use a fan to disperse water vapor. Warm mist humidifiers are louder than ultrasonic humidifiers, but quieter than evaporative models.
- Maintenance reminders. Look for indicator lights that alert the user when water is low or the filter requires cleaning or replacement.
- Adjustable-output humidity. More humidity isn't always better, which is why experts say it's important to set a humidifier at the appropriate level (generally between 30 and 50 percent). Signs that an area is over-humidified include peeling paint and condensation on the interior window surfaces. Too much humidity can promote the growth of mold, bacteria and dust mites.
- A humidistat or hygrometer to monitor room moisture. This feature improves efficiency and performance by turning off your humidifier when the humidity reaches the desired humidity, and turn it on once again when the humidity drops. However, reviews note that the humidistats in some consumer humidifiers can be inaccurate.
- Ease of filling. Choose a model with a removable reservoir. Other helpful features include a wide mouth, a carrying handle and a tank that will fit under your faucet.
- Automatic shut off. The best humidifiers can detect when the water tank is empty and turn themselves off to prevent damaging the unit, or potentially creating a fire hazard.
Know before you go
Cool mist or warm mist? Some people prefer warm mist humidifiers, saying the heated vapor is easier to breathe (especially if you're congested) and that it gently raises room temperature. But experts say that any benefits that warm mist provide compared to cool mist humidifiers is minimal. In addition, warm mist humidifiers that boil water can present safety issues (see below), and warm mist humidification is less energy efficient.
How big is the area that you want to humidify? Match the stated output of the humidifier to the area you want covered.
What kind of water does your municipality have? If you have hard water, a demineralization filter that minimizes dust caused by the minerals left behind by tap water is a must with any ultrasonic humidifier. Some models come with a demineralization filter; in other cases, it's an optional add-on. Remember to replace the cartridge as scheduled.
Consumable costs can add up. Even among the best-rated humidifiers, complaints about the costs of filters are often seen. Demineralization cartridges and bacteria-killing products also add to the on-going cost. If you live in an area with hard water, some say that using distilled water can cut down on dust emitted by ultrasonic humidifiers and extend the life of your appliance.
Safety first. We didn't see many complaints regarding safety hazards with ultrasonic or evaporative humidifiers. However when it comes to warm mist humidifiers and vaporizers, caution flags aplenty are raised. These work by boiling water to create steam. That water can scald if innocent hands accidentally tip over the humidifier, making warm mist types a bad choice if children are about. Dual-mist ultrasonic humidifiers are a bit safer, as they don't heat water up as much to create a warm mist, making it warm to the touch, but not scalding. On the other hand, by raising temperatures to boiling, warm-mist humidifiers do a better job of killing any bacteria in the tank or the water. Because of that, it is important to follow maintenance recommendations when using a cold mist humidifier to avoid issues with bacteria or mold.