Relative humidity of 30 to 50% is recommended for good health. This is challenging in extreme conditions such as dry heat or too much moisture. A humidifier is used to increase the level of humidity in the air and a dehumidifier reduces the humidity level of the air. A hygrometer can be used to measure the humidity of a particular area to decide whether a humidifier or dehumidifier is required.
edit What is a Humidifier?
A low humidity level results in dry and itchy skin or chapped lips. Humidity level greater than 50% results in growth of mold spores, bacteria and dust mites. 40% humidity is required for musical instruments to prevent their crazing or cracking of finish.
In the following video, Dr. Ari Brown explains the uses of a humidifier in a baby’s room.
edit What is a Dehumidifier?
A place with higher temperature and high relative humidity needs moisture to be pulled out of air. Moist air helps the growth of mold, dust mites and spores which aggravate allergies. A dehumidifier removes moisture from air and is suited for this climate.
edit Do you need a humidifier or dehumidifier?
The relative humidity of a particular place is the deciding factor in selecting either one. 35 to 50% humidity level is considered to be healthy. Based on the humidity levels of a room, a dehumidifier and humidifiers help obtain these levels.
edit Optmimum humidity level
The flu virus thrives best when humidity is either over 98% or between zero and 50%. So Dr. Linsey Marr, a researcher at Virginia Tech, recommends keeping humidity levels around 50% (but not over 60%, because that can cause mold buildup) to give the flu virus the least chance of survival.
edit Types of Dehumidifiers
- Mechanical /refrigerative - This is the most common type and usually works by drawing moist air over a refrigerated coil with a small fan. The air condenses on the coils and is collected in a dripping bucket. This type is effective when the ambient temperature is higher and the relative humidity is higher than 45% the air is cold
- Air conditioners – They inherently act as dehumidifiers.
- Adsorption/desiccant - A desiccant is a special humidity-absorbing material which is exposed to the air being conditioned. It moves along a belt. It is heated elsewhere to remove the humidity and is reused. This type is suitable for places with high humidity at low temperatures. Their ability to achieve a humidity level of 35% or lower enables them to be used in industrial sectors.
- Electronic - Electronic dehumidifier uses a Peltier heat pump to generate a cool surface for condensing the water vapor from the air. It has no moving parts and hence is quieter. But it has low energy efficiency and this design is used for smaller humidifiers.
- Ionic membrane – A specialized type of ionic membrane can be used as an ionic pump to move humidity into or out of a sealed enclosure are used in many industrial areas such as fuel cell technology, chemical engineering, and for water improvement. This is done at molecular level and hence no visible liquid water is produced.
- Makeshift - Window air conditioner units basically operate similar to mechanical/refrigerative dehumidifiers. Hence, these can be used as makeshift dehumidifiers by sending their heat exhaust back into the room.
edit How to choose a dehumidifier
This video by Consumer Reports offers tips on how to select a dehumidifier.
edit Types of Humidifiers
- Warm mist humidifiers
- Steam humidifier – It boils water and releases steam into the room. A medicated inhalant can be vaporized along with the water.
- Cool mist humidifiers
- Impeller humidifier – A rotating disc throws water on a diffuser which breaks water into fine droplets. The droplets exit as a cool fog mist.
- Ultrasonic humidifier – An ultrasonic diaphragm vibrating at very high frequency breaks down water into fine droplets which exit as a cool fog. This type of humidifier is silent.
- Wick/Evaporative humidifier – A wick is a filter that absorbs water from a reservoir. The wick provides larger surface area for the water to evaporate. A fan blows air to aid evaporation.
edit How to choose a humidifier
Here is a buying guide for various types of humidifiers that outlines the symptoms, size and benefits:
Both humidifier and dehumidifier need regular maintenance.
edit Maintaining a Humidifier
- Do not let water sit idle in the reservoir as this might lead to bacterial infection and mold formation. Clean the tank and filter regularly.
- Rinse the tank after cleaning to avoid harmful chemicals being released.
- Keep the area around the humidifier dry.
- Use distilled or demineralized water.
edit Maintaining a Dehumidifier
- Keep the coil and bucket clean.
- Check the coil for frosts as frost reduces efficiency.
edit Capacity Rating
The output capacity of a humidifier is measured as gallons of moisture per day. A unit with higher tank capacity needs less frequent refilling. The capacity of dehumidifiers is measured as number of pints of water removed in a 24-hour period.
The energy consumption of a humidifier is lesser than that of a dehumidifier. Irrespective of energy efficiency, both these appliances are used under mutually exclusive conditions depending on the requirements.