• Cooling India
  • Jan 15, 2016

Living With Humidifiers And Dehumidifiers

For most people, a relative humidity level between 40–50% in the summer and 30–50% in the winter is ideal. If the humidity drops below that level, the dry air can irritate our nose and throat, and dry out our skin, eyes and lips. Dry air may also shrink wood, damaging furniture, floors and walls....

- Dr. S.S. Verma

 Human always desire a comfortable climatic conditions for his living and when natural climatic conditions with time and region are not in human control, he has always strived hard to achieve it with the help of technology. Humidity conditions (low or high) are also uncomfortable climatic conditions to human, and he looks for means to either increase or decrease humidity in his surroundings. Hot and cold, dry and humidity conditions make the surrounding unbearable to the inhabitants and make them dull and unpleasant. These conditions become more severe when the place has no facility for the environment air to handle at all, no ventilation, no air conditioning; just stay there naturally and exasperatedly.

  The air in our home should range from 30 to 55 percent humidity. If the humidity is too high, mold and dust mites may thrive. Both are common causes of allergies. Mold also causes an unpleasant smell and can discolour surfaces. If the humidity falls too low, on the other hand, the people in home may suffer dry eyes and may develop throat and sinus irritations. Humidity levels determine whether we need a humidifier or a dehumidifier. We might need both machines at different times of the year.

  In this direction, humidifiers and de-humidifiers play a significant role in making the surrounding environmental conditions more comfortable. Thus, humidifiers and dehumidifiers are useful appliances that help maintain optimal humidity in home.


  For most people, a relative humidity level between 40–50% in the summer and 30–50% in the winter is ideal. If the humidity drops below that level, the dry air can irritate our nose and throat, and dry out our skin, eyes and lips. Dry air may also shrink wood, damaging furniture, floors, and walls. Additionally, low humidity can make our home feel colder, especially in the winter. A humidifier counter acts these effects, adding moisture to the air to boost the humidity back to comfortable levels. A humidifier is a device that increases humidity (moisture) in a single room or an entire building. In the home, point-of-use humidifiers are commonly used to humidify a single room, while whole-house or furnace humidifiers, which connect to a home's HVAC system, provide humidity to the entire house. Medical ventilators often include humidifiers for increased patient comfort. Large humidifiers are used in commercial, institutional, or industrial contexts, often as part of a larger HVAC system.

Types of humidifiers

  Today, there are countless models of humidifiers to choose from. Humidifiers are mainly classified into two types – warm mist and cool mist. In homes with children, it is better to avoid warm mist humidifiers since a child may get burnt from the hot steam emitted. Also, warm mist humidifiers consume more electricity as they have to heat the water to produce steam. Cool mist humidifiers are considerably safer, but require more maintenance. These units require cleaning with soap and water every day and changing the filter annually. After deciding to purchase either of these, the next thing to consider is whether the humidifier should be ultrasonic, evaporative or steam-based. Here are the differences, benefits and disadvantages of each:–

  • Ultrasonic humidifiers: These are among the cheapest yet most energy-efficient of all humidifiers. These units feature storage for water and oscillating plates. The vibrations of these plates transform water into a fine mist that is then blown out with a fan. The major problem of an ultrasonic humidifier is that it produces white dust as a by-product, which can pose a serious threat for people with breathing problems. However, the newer and costlier versions of ultrasonic humidifiers feature advanced technology that eliminates the problem of white dust.
  • Evaporative humidifiers: These units work by releasing moisture into the air by blowing water with a fan. This is quite a hygienic choice since it does not pose the problem of dust being released into the room. In addition to being very energy-efficient, this system is noiseless, so it can be comfortably used in bedrooms.
  • There are two kinds of evaporative humidifiers – one with porous filters and the other with rotating discs. When it comes to maintenance, the system with porous filter is less preferable, since it can quickly get polluted with hair, skin, dust and other matter in the air and incur regular replacements. On the other hand, the rotating discs of the second group of humidifiers are made from hardened plastic, making them easy to clean and care for.
  • Steam-based humidifiers: The moisture released by steam humidifiers can easily be regulated according to the extent of dryness in a room. The humidity control provided by these units is exceptionally hygienic since steam kills off germs and releases sterile moisture. That makes a steam humidifier an excellent choice for controlling humidity in nurseries or for people with respiratory illness.

  Maintaining a steam humidifier involves regular removal of lime scale that may build up within the system. Compared to other humidifiers, steam ones are considerably economical. However, steam humidifiers consume more power than other versions of humidifiers.

Benefits of using a humidifier

  Reduce risk of infections: Viruses and bacteria can’t travel as well in moist air. A humidifier could mean the difference between getting the flu this winter and remaining healthy.

  Softer, more vibrant skin: Cold, dry air saps moisture from skin, which causes all kinds of problems, including dryness, dullness, flaking, and accelerated aging. A humidifier can help prevent all these damaging effects, and help maintain that glowing, vibrant look.

  Comfortable sinuses: We always feel dry and tight feeling in our nose in the winter. Winter air can dry out our sinuses, lowering our resistance to bacteria and viruses. A humidifier will help overcome sinuses.

  Faster healing times: (Say) you do end up with a cold, a sinus infection, or the flu. A humidifier will shorten your suffering. Keeping your nasal passages and your throat moist will help you heal faster, and will reduce symptoms like coughing and sneezing.

  Healthier houseplants: Plants help pull toxins out of the air. But they can suffer in dry, winter air. Have you noticed that the soil is dryer than usual? Are the leaves looking droopy and sick? A humidifier can help keep your house plants healthy – which helps keep you healthy, too!

  Protected wood furnishings: Dry air can damage wood furniture, as well as moldings and doors, causing them to split and crack. A humidifier can help preserve the integrity of the wood, maintaining your pieces for years to come.
No growling morning voice: Do you often sound like a bear in the mornings? That’s dry air getting to your vocal cords. Sound more like your normal self when you sleep overnight with a humidifier in your bedroom!

  Reduced heating bill: Did you know that moist air feels warmer than dry air? It’s true. If you add some moisture to the air, it will feel warmer, which can help you save on your heating bills this winter.

  Fewer electric shocks: No one likes a static electricity shock – especially not the cat! But you may have noticed that in the winter, it’s harder to avoid it. That’s the dry air again. Use a humidifier and leave the lightning outside.

  Improved sleep: If you or a partner snores, a humidifier may help. We tend to snore more if our sinuses and throats are dry. A moist environment also tends to feel warmer and more comfortable, which can encourage a good night’s sleep.

Precautions with humidifies

  Humidifiers are not easy to use. All units, portable as well as those installed in central heating systems, must be cleaned rigorously. Otherwise, they tend to become contaminated with mold and bacterial growth that may be blown through the house. Stop the humidifier and call the mechanic if there is development of any respiratory symptoms that may be related to the use of a humidifier.

  • Use distilled or demineralized water: Regular tap water has minerals that create buildup in machine and promote bacterial growth. Distilled and dematerialised water contain fewer minerals and will save from having to clean as often.
  • Clean once a week: This will help to do the next cleaning quickly and will keep home healthy. 
  • Change filters regularly: Follow the manufacturer’s directions for changing the filter.


  On the other hand, high humidity may spur mold and mildew growth, which can exacerbate allergies and rot our walls. Harmful dust mites, those microscopic organisms that particularly aggravate allergy and asthma sufferers, thrive in high humidity. They live in our bedclothes, drapes, rugs, and the air in home. Removing excessive moisture from indoor air helps control these pests. Dehumidifiers also can help limit mold and bacterial growth. High humidity can also make the air feel much warmer, especially during the summer. Substantial condensation inside our windows is a good indication that humidity levels in our house are too high. Dehumidifiers remove moisture from the air. A dehumidifier is a device that extracts undesired level of moisture from the air to reduce the humidity level in the house. This curbs the growth of mold and dust mites. They are particularly useful in parts of the house where humidity collects, such as damp basements. Dehumidifiers are critical for households in humid climates with very old people or very young children, or for families with a history of allergies or asthma. Dehumidifiers draw air over cold coils, condensing out its moisture, before passing the air over warm coils and back into the room. Air conditioners also take a certain amount of moisture out of the air, but dehumidifiers do this much more efficiently. The condensed water drips into a container in the unit that has to be emptied. The water can be routed directly to a drain by means of a hose. Home dehumidifiers remove between 10 and 50 pints of water from the air each day, depending on the relative humidity. The capacity of a unit is measured by the number of pints it can remove in a 24-hour period at 60 percent relative humidity and at 80 degrees.

Dehumidifier basics

  Most dehumidifiers can be broken down into five component parts:

  • Fan Compressor – This compresses and expands a refrigerant gas like freon to cool the dehumidifier's coils. 
  • Reheater – This captures and collects heat that the cooling process generates.
  • Compressor cooling coils
  • Reservoir

  A dehumidifier works on the following lines:

  • A fan collects air from the surrounding area and pulls it into the dehumidifier.
  • As the air passes through, it comes into contact with the dehumidifier's cooled coils. These coils use condensation to pull moisture from the air. The collected moisture remains on the coils and drips into the dehumidifier's reservoir.
  • The dehumidifier reheats the air and exhausts it back into the room.

  A dehumidifier usually has a removable plastic bucket for a reservoir; most buckets also have a place where we can hook up a hose so the collected water can drain straight into a floor drain or pump. Many dehumidifiers also have a humidistat, which allows to set desired level of relative humidity. A humidistat has two parts: a sensing element and a relay amplifier. The sensing element includes two alternate metal conductors, and changes in relative humidity will cause electrical resistance between those conductors. The relay amplifier measures this resistance and sends a signal to turn the dehumidifier on or off. These basic components add up to a device that may make home feel a whole lot better.

Types of dehumidifiers

  The basic functional principle of a condense drying dehumidifier is really quite simple. A fan draws in humid air and carries it through a refrigerated evaporator. The air is cooled well below its dew point. The water condenses on the cold surface of the evaporator and drips into a water container or is led directly to a drain. Then the cold dry air continues through a hot condenser which heats it up and returns it to the room to pick up new humidity. This procedure is continued until the desired condition is achieved. To remove all of the water even with relatively dry air conditions, it is important that not all the air is cooled down by the evaporator as there is a risk that the dew point cannot be fully achieved. Instead only part of the air is led through the evaporator to ensure maximum condensation while the rest is by-passed as shown above. This results in a mixed 18°C and 85% RH air flow between the evaporator and the condenser. When passing the hot condenser the mixed air flow will ensure that the condenser is sufficiently cooled. The final result is an outlet air temperature from the dehumidifier of 33°C and 35% RH. The temperature is increased because energy is added by the compressor and by the latent heat from the condensation process. Dehumidifiers come in three main types: heat pump, chemical absorbent and dehumidifying ventilators. They all remove moisture from the air, but each has a slightly different method. The heat pump method draws in air with a fan and runs it across a cold coil to condense the moisture. Air is warmed by a heat pump and returned to the room. Chemical absorbent dehumidifiers send damp air outside after a chemical drying agent absorbs moisture from room air. Dehumidifying ventilators use a sensor and exhaust fan to determine when humidity levels are high.

  While refrigerative dehumidifiers may be the most well-known, desiccant dehumidifiers also do a great job of keeping a space nice and dry. True to their name, these dehumidifiers pull in air and pass it over a desiccant material such as silica gel. Desiccants naturally absorb moisture – that's why you'll find little packets of silica gel in new shoes or electronic goods. Because desiccant dehumidifiers don't need to cool air before dehumidifying it, this technology is really ideal for sub-zero conditions. Since the technology behind them is so simple and effective, dehumidifiers mostly vary in size and strength. Portable dehumidifiers are the kind that you usually see in the home improvement aisle; they're often plastic, relatively cheap and very lightweight. They're designed to be most effective in smaller spaces like a bedroom or kitchen. Restoration humidifiers are heavy-duty machines that can withstand harsh conditions – they're usually used to repair heavy water damage caused by hurricanes or other natural disasters. The largest models on the market, whole-house dehumidifiers, usually augment a home's existing HVAC system. You'll have to hire a professional to install one of those. Some manufacturers have also created specially sized crawl space dehumidifiers to address the humidity in storage areas and powerful dehumidifiers that are targeted toward the high humidity created by some indoor pools and spas. Whichever kind of dehumidifier you choose, it may help make your home a little greener.

Precautions with dehumidifiers

  Mold can grow in the drainage areas of a dehumidifier, so regularly clean the water basin with bleach. Also, smaller units may not dry out the air satisfactorily all the time so choosing a larger capacity unit is better.

Dr. S.S. Verma is from Department of Physics S.L.I.E.T., Longowal, Distt. Sangrur (Punjab) - 148106

If you want to share thoughts or feedback on this article, please leave a comment below.