posted on
December 22, 2009 at 03:30PM
Cool mist is not a dehumidifier. It will add moisture to the air, but without adding heat. They generally use an ultrasonic vibration to turn the water in the tank into a mist, which is then blown out with a fan. It can contribute to a drop in room temperature if the room is small enough. These are best used in summer months.
Warm mist uses a heating element to turn water into steam. That steam rises out of the humidifer and into the air. That steam increases the humidity of the air in the room. This can result in a net increase in air temperature, so it's best used during winter months, especially when the air is super-dry and the room may lose heat faster.
There are also evaporative humidifiers, which draw air through a water-wicking filter, and send the moisture-laden air into the room. This is the simplest form of humidifier, and has the least effect on room temperature, though can contribute to a net decrease in temperature. It is also less likely to result in wetness on floors or other surfaces, because the water is not being expelled in microdroplet form or steam, but as humid air caused by evaporation. The only disadvantage is the need to replace the wick filters, usually every month during use.