Impeller room humidifiers are often referred to as "cool mist" humidifiers because they use a high speed rotating disk to create a cool mist comprised of tiny droplets of water. These droplets of water can be messy and often gather in a pool at the base of the humidifier, which can lead to mold and the buildup of harmful pathogens.

Ultrasonic humidifiers have the ability to produce extremely small water droplets which evaporate into the air more easily than large drops of water, which often end up on the ground around the humidifier instead of in the air. Though more effective than an impeller humidifier, ultrasonic humidifiers can be much more expensive.

Evaporative humidifiers transmit unseen moisture into the air by the means of a fan designed to blow air through a moistened, absorbent material such as a wick or filter. Evaporative humidifiers are less likely to disperse microorganisms or minerals into the air.

Steam vaporizers use an electrical heating element to heat the water in the tank to produce steam. These vaporizers can be a potential burn risk, especially when used around children. A "warm mist" humidifier on the other hand is able to cool the steam before it exits the machine. Steam vaporizers also have a tendency to be messy, like the impeller humidifier, but they are less expensive than the evaporative type.

Each humidifier type has its own manufacturer's specifications regarding the proper cleaning and maintenance. Some units might be easier to clean, have less expensive filters, or be able to operate for longer periods of time between cleanings. Deciding which type is better depends on your individual needs and priorities.

Next, look at how frequently you will be using the humidifier. Some people only need a humidifier to help provide relief from symptoms associated with colds, coughs, and other respiratory illnesses. In that case a smaller, less-expensive portable unit for your bedroom will probably be adequate.

If your purpose in purchasing a humidifier is to provide relief from dry indoor air caused by heating your home in colder winter months, you might want to invest in a more expensive, higher-capacity humidifier. Furnace-mount humidifiers work well for high-frequency use and often require less maintenance on the part of the homeowner than the portable units.

This leads us to the last question: how much cleaning and maintenance do you have the time for? To ensure that your humidifier is benefiting your health and not contributing to poor health, the importance of proper cleaning and maintenance cannot be stressed enough. Using distilled or filtered water will make the job of cleaning and maintaining your unit much easier, but there is much more involved.

Filters need to be checked and changed frequently; mineral deposits, scale, and slimy buildup needs to be cleaned promptly; water in the tank and reservoir needs to be changed frequently to prevent the growth of bacteria; and the tank and all other washable parts of the humidifier need to be cleaned with a vinegar or bleach solution on a regular basis.

Always check your owner's manual for the manufacturer's specific cleaning and maintenance guidelines. Remember that the more often you use a humidifier, the more frequently it will need to be cleaned. For humidifiers that are only used occasionally, clean thoroughly before using and repeat the cleaning before putting it away.

When choosing a humidifier that is right for you, remember that humidification is not yet a perfected technology. Purchasing a higher-priced unit with the expectation that it will basically take care of itself without regular work on your part is almost like asking for an eventual breakdown. Neglecting proper care and cleaning will eventually lead to your need to replace your machine with a new one.

By choosing a humidifier that is right for your needs and then properly caring for your machine, you will be able to compensate for most technological faults and still be able to enjoy the health benefits of properly humidified air.