Temperature-Humidity Gauge

When should you turn on the humidifier?
When the outdoor temperature drops below 40°F during the day, night, or both, it is time to turn on the humidifier. As a rule of thumb, bedroom air will likely require humidification when the furnace is operating.

What is the best type of humidifier?
Five types of humidifiers are in common use today. These are the warm mist humidifier, the steam vaporizer, the evaporative humidifier, the cool mist humidifier, and the ultrasonic humidifier. The warm mist humidifier is a safe variant of the steam vaporizer. In both, the machine boils the water and only emits steam which is pure water vapor. Any bacteria or molds which contaminate the water in the reservoir will not be passed into the air and from there into your child’s throat or lungs. The warm mist humidifier is safer than the less expensive steam vaporizer because it mixes relatively cool room air with the hot water vapor before the machine emits it. The best warm mist humidifiers contain a fan to completely mix the room air with the steam and to distribute the blend around the bedroom more efficiently. Some recent warm mist humidifier models do not have an internal fan, and it is advisable to purchase a small portable fan to place near the vapor outlet in order to properly and safely mix the water vapor with room air. Warm mist humidifiers also contain a "humidistat", a device which turns the steam generator off once the humidity in the room reaches the desired level, which is 40-45%. Purchase a model which has a continuous humidity control rather than only a small number of settings such as low,medium, and high.

The less-desireable cold mist or ultrasonic humidifiers spray very tiny droplets of water from the reservoir into the air, and germs, including bacteria and molds growing in the water, travel in these microdroplets. Cool-mist and ultrasonic units also spray any chemicals or minerals present in the water into the room. This airborne debris then coats all walls and furnishings.

Cool-mist or ultrasonic humidifiers must be carefully cleaned on a daily basis, an impossible task for most of us. The evaporative types, usually console devices designed to be used in hallways, tend to readily develop mold on the wicks or belts, and these must be cleaned or changed frequently.

Steam-based humidifiers need not be cleaned as often or as carefully. The minerals and other chemicals which remain after the pure water vapor is boiled off must be rinsed out and sometimes scrubbed off the heating coils or plates.  The latest type of steam-based or warm mist humidifier boils the water off a wick.