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What Are The Different Types Of Humidifiers? A Complete List

types of humidifiers

Humidifiers are used to control indoor humidity in a variety of settings including in your home, office, industrially and in all kinds of public spaces. Accordingly you will find them in all shapes and sizes out there. Do a little research and you will even notice multiple distinct names being used to refer to one type of humidifier. 

This can make it seem like there are so many different types of humidifiers out there and worse yet make things rather confusing when you have to make a decision concerning humidifiers. I see this confusion a lot online when people list types of humidifiers and often three out of the five types they list are actually one type with three different names.

Initially I set out to write this post as a one stop guide to different types of humidifiers but in light of all the confusion and misleading information I took care to also properly classify and clearly point out each distinct type of building based humidifier with the various common names given to each of them.

In summary, the different types of humidifiers fall under two categories, warm mist and cool mist humidifiers. Under the two categories, there are various types of humidifiers with different technologies. These various types of humidifiers are then further categorized into portable and whole-house humidifiers.

Once you have these broad humidifier categories in mind, you’ll avoid half of the mistakes people make when identifying types of humidifiers. Taking these categories into account in the rest of this post I dive into the nitty gritty showing you everything that falls under these categories.

By the time you are done reading through here, you shouldn’t be confused between the different types of humidifiers anymore. So, if you are serious about knowing your different types of humidifiers or just curious about the difference between a couple of them that you came across then read this post. I am confident you will find clarity.

What Are The Different Categories Of Humidifiers?

Nowadays you will find so many different types of humidifiers out there. Out of all the seemingly different humidifiers they can all be classified into four categories. Two of the categories are based on size and the other two are based on the type of humidification technology they use. 

The two technology categories you will find include warm mist and cool mist humidifiers while the two size categories include portable and whole house humidifiers. One thing you will also find and that took me quite a while to figure out about humidifier categories is the multiple names used to identify them.

Don’t let the multiple names confuse you. When it comes down to how the humidifiers operate, you almost always end up classifying humidifiers in the four categories I have mentioned. Let’s look at each of the categories in more detail starting with the technology based category.

Categories by Technology 

Warm Mist Humidifiers

The first category of humidifiers I am going to talk about are Warm mist humidifiers. The other common names used for this category of humidifiers are isothermal humidifiers and steam humidifiers. 

Steam humidifiers are known as one of the cleanest humidification systems due to their use of hot water which kills all sorts of germs as your humidifier does its job. Warm mist humidifiers work by heating water to create vapor which is eventually released into your air as sterile moisture. 

You will find several types of warm mist humidifiers out there. In comparison to cool mist humidifiers (the other technology based category of humidifier) they are praised for achieving high levels of moisture saturation and being generally more silent.

Steam humidifiers are a good idea in winter. They are also helpful when it comes to dealing with flu and cold symptoms. They also produce lower levels of mineral dust compared to cool mist humidifiers. 

However, they are more costly to run from an energy consumption perspective as they have to heat up water in one way or another to work. Also, if you are using an air conditioner a large enough humidifier will increase your cooling cost as you add more moisture and heat into your air for your aircon to work against.

Using a steam based system in close proximity to your baby is also not ideal as heated water is a safety risk around a child. Pound for pound, warm mist humidifiers are generally more expensive than cool mist humidifiers. To add on to their running costs you may incur, they use filters that need to be replaced every now and then. 

Cool Mist Humidifiers

Cool mist humidifiers, also referred to as adiabatic humidifiers work by emitting a cool vapor to add moisture to your air. Water is added to the humidifiers reservoir. Then before the water makes its way out of your humidifier, it travels through a wick filter within the humidifier to get rid of some impurities. 

Thereafter dry air sucked into the humidifier by a fan is blown out causing the water saturated in the wick like filter to evaporate into your room. Other cool mist humidifiers work by using high frequency vibrations. The vibrations are so high that they break up the water into tiny droplets which are propelled into the air. 

These tiny water droplets then evaporate adding moisture in your air. So from this you can see cool mist humidifiers use direct evaporation of water to add moisture to your air without heating any water and consequently without raising your room temperature.

There are many other types of cool mist humidifiers but whatever mechanism they use they all boil down to adding moisture to your space through direct evaporation. This category of humidifiers are well suited for use in warm weather as they won’t raise the temperature in a room.

Cool mist humidifiers are also generally easier to clean than warm mist humidifiers. You literally just wash them as you do your dishes. The catch however is that they need frequent cleaning especially due to mineral dust accumulation and easy bacterial build up. 

If you don’t clean them often, these impurities can be transmitted into your air causing all sorts of health problems. That said allergy and asthma sufferers have found cool mist very helpful in alleviating their symptoms. 

Lastly with cool mist humidifiers expect to have a dull background humming noise whenever you run your appliance. So if you don’t want another noise making appliance in your home you’d rather opt for the more silent warm mist humidifier.

Categories by Size

The other way humidifiers are differentiated is by their size. Humidifier size is not really about the physical size of the appliance but rather about the area and number of rooms they can cover in one go and their mobility.

Two humidifiers can use the exact same humidification technology but because their level of mobility and the area they cover differs significantly they are classified in separate categories and are seen as different. In terms of size, humidifiers fall in two categories. 

The two categories are Portable and Whole-House humidifiers. Let’s look at each in more detail.

Portable Humidifiers

Portable humidifiers, also known as personal humidifiers, range in size from small table top to large floor based units. They are also called portable humidifiers. This category of humidifiers as the name suggests are the type that can be moved around.

Now, as much as they are movable, not all the humidifiers in this category are easily movable. Some are in fact quite large and heavy and need to be pushed around on wheels. What makes them movable is that they are not permanently fixed somewhere in your office or living space.

Some portable types of humidifiers are small enough for you to carry and around when you are travelling and on the move and they are battery operated while others are large and designed to be placed and moved around within a home or office environment.

These humidifiers can be either cool mist or warm mist. They are most suitable for you if you need to humidify your personal space or just one room at a time in a building.

Whole House Humidifiers

Whole-house humidifiers are the complete opposite of personal or portable humidifiers. These humidifiers are also called in-duct humidifiers, fixed installation humidifiers, industrial humidifiers or central humidifiers. 

Unlike portable humidifiers they are usually permanently installed in a building’s HVAC system to humidify multiple rooms at the same time. They are usually large and once installed cannot be moved around.

However there are some humidifiers that are referred to as whole-house humidifiers due to their ability to humidify an entire home but are placed directly inside your work or living area like portable humidifiers. 

These are usually called console humidifiers and they work in exactly the same way as other whole house humidifiers but without being placed in any duct work. This type of whole house humidifier is usually used for homes or buildings where you have no ducting but you want to humidify your entire home. 

As console humidifiers operate similarly to other whole house humidifiers that you install on your ducting I won’t touch on them in this post but I will focus more on the whole house humidifiers that you hook up to your furnace or HVAC. So when I say whole house humidifier I am referring mainly to the type you install on your ducting unless I say otherwise. 

If you have a forced-air furnace, an in duct humidifier can also be installed into your furnace. These humidifiers are usually connected somewhere between your HVAC’s air return and supply duct close to your furnace and air handler. 

They are usually installed with a humidistat to allow you to automatically control the level of humidity around your home. In addition there is some plumbing work done for an automated supply of water to your humidifier and for drainage of any excess water.

You can do a DIY installation of an in-duct humidifier and also maintain one yourself but it’s better you call in an HVAC expert to handle all this as the process is quite technical. So with a whole house humidifier, you better be financially prepared to add it to your HVAC maintenance bill. 

That said, if you must have building wide humidification they are the ideal option. This is especially true for large homes or buildings. Otherwise, you could be running a portable humidifier in multiple rooms which is not cost effective or energy efficient compared to a whole-house humidifier.

Whole house humidifiers are also known for energy saving In winter or cooler months since they increase building wide indoor humidity levels making you feel warmer at lower temperatures. This means you use less energy to keep your home warm.

Looking at the four humidifier categories, you now know the different types of humidifiers on a broad scale. In summary on a broad scale, the different types of humidifiers include:

  • Steam/ Warm Mist Humidifiers
  • Adiabatic/ Cool Mist Humidifiers
  • Portable Humidifiers
  • Whole-House Humidifiers

Of these different types, Portable and Whole-House humidifiers overlap with warm mist and cool mist humidifiers. So for example, you can have a humidifier that is both personal and either warm mist or cool mist.

Now that you know what the different types of humidifiers are on a broad scale we can drill down and look at the range of different humidifiers that fall under each of the broad categories.

The Complete List Of Different Types Of Humidifiers

Portable Humidifiers

1. Vaporizers

Vaporizer humidifiers are a common type of portable warm mist humidifier. This type of humidifier works by boiling water and releasing the steam produced thereof into your air. 

The beauty of vaporizers is that you can also add medical inhalants to their water tank to spread them in the form of steam and vapor and eventually inhale them. Furthermore, vaporizers allow you to choose between cool and warm vapor. 

When you set a vaporizer on its highest setting it dispenses visible steam and on it’s cool setting it instead dispenses mist. Since you can use them to emit medical inhalants into your air, vaporizers are quite commonly used to treat colds and flu.

They are among the more affordable types of humidifiers. Because they use heat, they are less likely to cause bacterial contamination. Vaporizers are also known not to emit significant levels of mineral dust into your air and they are definitely the go to type of humidifier if you are looking for a quiet humidifier.

The problem with them however is that they are a burn risk, especially for babies because they involve boiling water and steam. To add on, they use quite a lot of energy to produce the steam and mist they disperse to moisten your air. Another risk associated with vaporizers is that they are a fire risk.  

If you get a low quality one, it may have a poorly designed heat source that can overheat and cause your humidifier to melt and leak and potentially start a fire. Lastly because of the complex way vaporizers are built, they are harder to clean than most types of humidifiers.

To make their cleaning process even more cumbersome, sometimes vaporizer humidifiers will collect mineral deposits around their heating element and this has to be cleaned out by pouring citric acid or vinegar into your humidifier to soak and dissolve the deposits.

2. Evaporative Humidifiers

Another common type of humidifier you will come across is the evaporative humidifier. It is also known as a wick humidifier or cool moisture humidifier. 

This kind of humidifier is a cool mist humidifier. It is made of a wick, fan, and a water tank which some people refer to as a reservoir.

The wick is a porous material designed to suck water from the humidifier’s water tank. Once it sucks up water it’s large surface area then allows for a huge volume of water to evaporate. 

Then to support the evaporation process, the fan continuously blows air onto the wick and on to the water evaporating from your wick into your air. The water water vapor is then expelled as a spray or mist, creating humidity in your air.

That said, not all evaporative humidifiers are designed with a fan. Some come with no fan and just have a reservoir and wick and they are sometimes called natural humidifiers. You can check out an example of this here on amazon

You can actually make one of these at home by simply placing water in a stainless steel bowl with a towel over the bowl and partially dipped in it to slowly suck the water and eventually evaporate it into your air.

Whether you are using a wick or natural humidifier the whole process of how they work depends on the relative humidity in your living or work space. So, a room with high humidity will have a lower evaporation rate than a room with comparably low humidity.

As you may have probably imagined, it means this humidifier controls itself. If your humidity level is already high it won’t release as much moisture into your air and if your ambient humidity level is low it releases more moisture.

The beauty of evaporative humidifiers is that they are low maintenance and easy to clean. They are also very affordable and safe to use around children and animals as they do not generate any heat. 

As they emit cold vapor unlike warm vapor based humidifiers, they are also not a danger to most surfaces. They are also self regulating and you will waste no time wondering if they are set to the right humidity generation level.

The problem with them however is that they are a magnet for bacteria. They get moldy fast and they are known to spread mold and bacteria into your indoor air if they are not well maintained. 

So with this type of humidifier, be prepared to clean your appliance frequently. Another thing you can do to avoid bacterial growth is to use distilled water. 

You can buy distilled water or use a water distiller like this one here on amazon to make your own. If you can’t do that, rather look for a warm mist humidifier or an alternative that does not host bacteria.

Besides being a source of bacterial contamination, evaporative humidifiers are also known to be noisy due to their fan system. Lastly, they are also a source of mineral dust that can spread on surfaces around your home through the water vapor they produce.

The mineral dust comes from naturally present minerals in your home water supply. A solution for this is therefore to use distilled water which is essentially water that has been stripped of all its natural occurring minerals. 

You could also install a water softener system for your entire home which makes your tap water pure enough to use in your humidifier without creating white dust or alternatively place a demineralization cartridge in your humidifier.

3. Ultrasonic Humidifiers

Another portable humidifier you will come across is an ultrasonic humidifier. This type of humidifier is commonly a cool mist humidifier but these days you have some that come with an additional warm mist option.

They work by using a ceramic or metallic vibrating diaphragm to release very tiny water vapor into the air which eventually evaporates around your room at a rapid rate and raises your humidifier level. It’s called an ultrasonic humidifier because the diaphragm vibrates at ultra sonic speed. 

The vibrations agitate the water into very small water particles and as a result you see fog or mist coming out of your humidifier. Not all ultrasonic humidifiers have fans but those that do normally have a silent fan that pushes the mist your humidifier generates up and out of the humidifier and into your room.

To control your humidity level, some ultrasonic humidifiers come with a humidistat to automatically adjust the amount of moisture in your air to maintain your desired humidity level. On the other hand others have settings which you have to manually adjust as preferred.

The pros of ultrasonic humidifiers include their extreme energy efficiency safety with children as they mainly function as cool mist humidifiers and low maintenance requirements. Furthermore, they operate very silently. You can barely hear them.

However, like other cool mist humidifiers, they are not exempt from polluting your home with bacteria and mineral dust. That said, they are easy to clean and the solution to fight bacteria is cleaning your humidifier often. To deal with white dust from ultrasonic humidifiers,  disposable demineralization cartridges are highly recommended.

4. Impeller Humidifiers

To add on to our list of portable cool mist humidifiers, impeller humidifiers work by using rotating disks that run at high speeds. The discs fling water at some form of diffuser which breaks the water into very small droplets that float into the air and quickly evaporate. 

Like all cool mist humidifiers they are safe around pets and children. However from my research I found that these humidifiers at times aggravate allergies and asthma for some people and also cause problems for people with breathing issues.

They are also among the nosier types of humidifiers and you have to keep them extremely clean to avoid them releasing bacterial contaminants in your home.

5. Air Washers

The final type of portable humidifier I found is an air washer. This type of humidifier not only adds moisture to your air but also washes particulate impurities such as pollen, dust and dander out of your air.

Air washers normally consist of a single or multiple spinning discs and tank/reservoir of water in which the discs sit in. Other variations also have wicks like evaporative humidifiers and some also have prefilters to get rid of large pollutant particles in your air. 

That said, the spinning discs are the main way air washers humidify your air. To humidify your air, what happens is that the discs spin around inside the water reservoir while a quiet fan sucks your room’s air over the spinning disc. 

Thereafter any dust, allergens and other air pollutants  in the drawn air clings to the water on the discs and as the discs spin the pollutants are subsequently deposited into the water sinking to the bottom of the reservoir and leaving the drawn air clean.

Not only is the air going through the air washer cleaned but it is also moisturized. Once moisturized the air is expelled back into your room from the air washer and accordingly raises the level of humidity in your room.

Just like other cool mist humidifiers, the air washer has to be cleaned very often as they have a water tank where bacteria and mold grow easily and these can get into your air. However, on the positive side, they do not cause a white dust problem in your air and are safe for use around children and pets as they do not use any heat to moisturize your air.

Air washers can be used to humidify your air with either hard or soft water as they actually filter out mineral dust from the water used to add moisture to your air. 

They are also great for larger rooms as they are able to release a significant amount of moisture into your in a given time period compared to most of the other types of humidifiers. With most air washers, maintenance costs are low as there are no filter changes and all you have to do to maintain them is wash them like you do your dishes.

So these are all the different types I could find. If you know of any other type I may have missed, please do comment below and I will add it here. Now let us take a look at the different types of whole house humidifiers. 

Most of them are essentially the same as the portable ones in terms of the technology they use and are just bigger and immovable but there are some types that do not come in a portable form. For those that are similar I am going to keep the discussion brief and avoid repeating myself.

Whole House Humidifiers

1. Centrifugal Atomizers

First on our list of whole house humidifiers are centrifugal atomizers which are also referred to as disc wheel humidifiers or impeller humidifiers. The way they work is the same as the portable impeller humidifier.

However, instead of being placed in your room they are connected to your furnace and spread moisture across your entire home through your office’s or home’s air duct system. These humidifiers use a spinning disc to atomize water converting it into millions of super tiny droplets. 

The droplets are then blown by a built-in-fan in the humidifier out through your ducts and air vents into your room and once in your air, they evaporate and subsequently cool and humidify your air. 

This type of whole house humidifier is also connected to an electrical control panel inside your home for you to easily control and manage it. It has a water tank and most humidifiers of this type come with a water tank washing and emptying cycle to avoid problems of having stagnated water inside the unit.

Furthermore the humidifiers water tank is filled with either water from your main water source or treated water source. Centrifugal atomizers are very similar to drum style whole house humidifiers which I touch in the next section.

The difference between the two is that the disc wheel part of a disc wheel humidifier doesn’t need to be replaced often while the spinning part of the drum humidifier needs regular replacement. 

The drum humidifier disc is made of foam while the atomizer disc is made of multiple plastic grooves. The way the centrifugal atomizer is designed makes it very easy to maintain with no regular replacement parts needed.

This type of humidifier is also known for its higher moisture output capacity due to its large evaporative surface area. Another benefit is that you can use it with hard water without fear of mineral dust spreading around your home. 

This humidifier type is also quite useful from a performance perspective as it maintains its efficiency throughout its lifespan. However, you may find it tricky to regulate your humidity level with a whole house disc wheel humidifier. 

This is due to their built-in high speed air stream which causes water in the unit to continue to evaporate excessively even when you set your humidifier to a lower humidification level. 

That said, eventually your humidity level does align to your required level but just expect a delay after you adjust your whole house disc wheel unit downwards. The only other discouraging thing about centrifugal atomizers I found is that they are quite expensive.

2. Drum Humidifiers

Drum style whole house humidifiers are cool mist humidifiers. As I mentioned in the previous section, they also have some form of spinning disc but it is rather referred to as a drum. The drum is covered in by a foam pad which acts as a wick.

Whole house drum humidifiers also have a water reservoir referred to as pan and the drum part of the humidifier is suspended in the pan to enable it to rotate there. To humidify your air the humidifier unit is attached to your building’s furnace in a bypass manner and spreads moisture across your building using your air ducts.

A pipe is connected from your main or treated water source directly into your humidifiers pan. As the water level drops in your pan it is automatically refilled using a tank float valve in pretty much the same way your toilet works.

When you turn on the humidifier and adjust your humidity settings, your humidifier’s built-in humidistat turns on the motor of your unit. The motor in turn rotates your unit’s drum slowly through it’s water filled pan to keep it moist. 

Simultaneously hot air enters the drum through one end and is moisturized through exposure to the moist foam on the drum and forced out through the sides of the drum and through your ducts and eventually into your home whereby water in this moistened air evaporates and increases your humidity level.

The foams that cover your drum have to be replaced monthly but luckily they are very cheap and easy to find. This type of whole house humidifier is also quite affordable if you are looking for a unit that won’t break the bank.

But you pay for the low cost. You have to inspect the unit every month for cleanliness and to see if the foam pads need changing. Drum humidifiers also develop mold very easily and if not kept clean they can spread mold spores across your home or whatever building setup you plan to place your humidifier in.

Furthermore, even when your humidifier is off, water in it’s pan remains exposed to a naturally present high speed air stream in your duct system. This means water continues to evaporate through your duct and some level of humidification continues in your home even when it’s not required. 

To avoid both mold and excess humidity issues, you have to constantly ensure you empty the water in your humidifier pan when you are not using it. This also entails shutting off the humidifiers water supply. 

You should especially do this in summer when you don’t really need your humidifier. Additionally, to minimize mold, it’s wise to install a high quality furnace filter with the highest MERV ratings your furnace can handle.

3. Spray Mist  Humidifiers

Another cool mist whole house humidifier is the spray mist humidifier. The way this type of humidifier works is simple. A plastic water pipe is connected from your main or treated water source to some electrically controlled valves in your humidifier which is in turn connected to your air duct.

Then when you turn on your humidifier, the electrically controlled valves which are also referred to as atomizers, force water flowing directly from your water supply through tiny orifices causing the water to break into tiny particles forming water mist in your humidifier. 

Thereafter the humidifier sprays this mist directly into your supply air duct and the mist is moved through your duct and around your building using your duct’s air flow. What makes’ spray mist humidifiers great is their ease of installation.

There is no need for any bypass or additional ducting on your furnace or HVAC system. You simply cut a single hole on the supply air section of your duct and fit your humidifier there. 

The humidifier is so small at about 6 by 6 inches (square) and can fit almost anywhere on your existing ducting unlike other types of whole house humidifiers. As you install it directly on your ducting, you avoid the risk of messing with the air pressure in your return and supply duct as in the case of bypass installed alternatives.

These humidifiers also use minimal electricity and are a great option if you are energy conscious. There are no wicks involved so you avoid the pain of frequently replacing wicks. 

Spray mist humidifiers also have no reservoir and as a result you avoid creating a breeding ground for mold in your furnace as you have no stagnant water lying around in your duct system. The nature of the spray mist humidifier is such that it does not produce waste water and it doesn’t even need a drainage system. 

If you have soft or treated water you rarely need to maintain your humidifier but the nozzles of your electric valve will need occasional cleaning if you run your humidifier on hard water. If you don’t clean the nozzles when using hard water they will get clogged and stop working.

Sometimes the minerals in hard water can clog up your nozzles so badly they will need to be replaced. Lastly, with spray mist humidifiers, you will get mineral dust in your home if you are using hard water. 

So if your area has hard water and you want to use this type of humidifier you will have to invest in treating  your water supply to avoid spreading white dust around your office or living space.

4. Bypass Flow-through  Humidifiers

The bypass flow through humidifier is yet another cool mist humidifier. Like the spray mist humidifier it also uses electrical control valves. However these valves do not necessarily break your water particles into tiny particles but rather spray water on to a solid usually rectangular pad within your humidifier called a “biscuit”.

Your humidifier is connected to your furnace in a bypass manner using additional ducting. Then when you turn on your humidifier from an electrical control panel in your home your humidifier’s humidistat signals it’s electrical valves to open up and spray water onto the biscuit.

Once the water is sprayed on the biscuit, hot air from coming from your furnace passes through the biscuit causing the water that was sprayed on it to evaporate and subsequently flow into your building. The main challenge you will face with this type of humidifier is white dust clogging up your valves nozzles and spreading through your indoor environment.

Again, this can be dealt with by installing a water softener system for your facility. Maintenance costs are low as the only time you will ever need to replace anything in this humidifier is if it’s badly clogged up by minerals when you use hard water. 

Another negative that you will have to deal with is that the humidifier does produce waste water and so you will need drainage. However on the flip side it has no water reservoir where water can lie stagnant and thereby minimizes the chances of you breeding mold in your air duct and spreading it around your indoor space through your air ducts.

5. Non-bypass Flow-through (Fan Augmented) Humidifiers

This humidifier is exactly the same as the bypass flow through humidifier. However it differs in that it has a built -in fan. The fan sucks air coming from your furnace or your air handler and pushes it out through your supply air duct and into your work or living space.

This enables you to connect the humidifier directly on the existing duct instead of doing a bypass installation. The advantage of this approach is that you can install your humidifier in more confined spaces than you can if you were to do a bypass installation.

This type of humidifier is also known to provide more consistent humidity across your home because of the additional and powerful airflow it generates from its own fan. However you will feel a slight pinch on your electricity bill with this kind of humidifier as these fans run on high voltage. A fan augmented humidifier is pricey compared to other types of humidifiers. 

I have also heard that it can be quite tricky to replace the biscuit as some model specific biscuits are not only expensive but hard to find. This challenge also applies to bypass flow through humidifiers. As for other advantages and disadvantages, they are the same as for the bypass flow through humidifier. 

6. Compressed Air Humidifiers

Compressed air humidifiers are yet another cool mist humidifier. People also refer to them as water atomizers. They work in the exact same way as spray mist humidifiers but in addition to a plastic water pipe supplying water to an electrical control valve there is also plastic pipe supplying compressed air.

The combination of the compressed air and water then breaks the water into ultra fine droplets creating an aerosol that quickly evaporates. Such humidifiers are usually used where high caliber humidification is required like in the textile, wood or paper processing industry or in cold rooms.

Compress air humidifiers share pretty much the same strengths and weaknesses as your spray mist humidifiers. Due to their level of sophistication and the environment they do come with a lot of automation. For instance some have self cleaning nozzles and others are designed to allow you to set different humidity levels in different rooms.

7. Ultrasound Humidifiers

Console based ultrasound or ultrasonic humidifiers operate exactly as the portable ones do and share the strengths and weaknesses but with some added weakness. Console ultrasound humidifiers are normally bigger than portable ones. 

To state the obvious, you connect them to your air handler or supply air duct to spread the moisture they create around the rooms in your building using your ducts’ air stream. However there are some models that come with a blower fan that you connect  to your duct for supplemental air flow.

Your humidifier will need a water source and this has to be soft or treated water to prevent them from spreading white dust around your home or work space. As they have a water reservoir you also need to connect some form of drainage to your humidifier and the stagnant water in the reservoir also poses a mold risk.

8. Gas-fired Humidifiers

Ohh and at last, here is our first warm mist whole house humidifier. From my research I found that they are certainly not as common as cool mist whole house humidifiers. The first warm mist whole house humidifier I came across when researching this post was the Gas-fired whole house humidifier.

I must say, I struggled to understand how they work initially and here is my attempt to put it in layman’s terms for you. This type of humidifier is usually connected to your HVAC or furnace supply air duct using a bypass approach.

It has quite a number of parts. The main part includes some metal heat exchangers, a water tank that looks like a geyser, a steam outlet pipe, an air, gas and water inlet pipe. It also has a drain outlet pipe from the water tank and some kind of exhaust for combusted gas.

To really simplify things, when you turn on the humidifier from your electronic control panel you start a chain of reactions whereby natural gas or propane is combined with air and supplied to a gas burner. 

Then an automated igniter on the gas burner lights up the gas and air mixture which then heats up some heat exchangers that are submerged in a water tank within the humidifier. 

The heat from the heat exchangers is then transferred to the water which in turn boils up and produces steam which exits the humidifier’s tank through its steam outlet into your supply air duct and into your home adding moisture across your home until your desired level of humidity is reached.

Among warm mist whole house humidifiers, people choose gas-fired humidifiers because they are cheaper from an energy consumption perspective compared to electric warm mist humidifiers.

They are not ideal for use with hard water as minerals will build up in your humidifier’s tank and you will often have to open up the humidifier to have the tank cleaned.

Sometimes, the minerals or limescale will build up to a point whereby they damage the exposed parts in your humidifier and you will have to replace these parts and this can get quite costly.

So when you have this type of humidifier be prepared to invest in a water treatment system. That said, even when running it on hard water, as a warm mist humidifier, it will not spread white dust across your home like most cold mist humidifiers do. 

What’s more you also don’t need to worry about mold and bacteria being spread through your air as the steam kills these off. Gas-fired humidifiers offer you intrinsically hygienic humidification. 

The only other thing that may worry you about gas fired humidifiers is their price tag. They are quite expensive to purchase and even to install. However your investment pays off in terms of how much you save energy wise. You can save up 75% on your energy bill if you use a gas-fired humidifier as opposed to an electric whole house humidifier. 

9. Electric Heater Humidifiers

Also known as Immersed heater humidifiers, electric heater humidifiers are set up and work in a similar way as gas fired humidifiers but differ in that they use an element to heat up the water in their tank rather than heat exchangers as I described for gas fired humidifiers in the previous section.

The electric heater element transfers heat to the water in the humidifiers tanks making this water boil and generate steam which is then released into your ducting and eventually into your home using your ducts air flow. 

They use any kind of water but if you use hard water with this kind of humidifier limescale will build up in your water tank and cover your elements and to keep your humidifier working you have to periodically open it up to clean the mineral build up and at times even replace the elements.

To minimize how often you  maintain an electric humidifier due to mineral build up, it’s advisable to use this type of humidifier with a water softening system. Another issue you should anticipate with electric heater humidifiers is overheating. 

This happens if the safety sensors in your humidifier don’t work well and there is not enough water in your water tank for whatever reason while your elements are heating up. The last key thing to worry about when it comes to immersed heater humidifiers is their energy consumption.

They are not that expensive to buy and install but the guzzle through electricity like electric geysers do. So be prepared for a considerably higher electric bill if you go for one of these types of humidifiers. Overlooking their shortcomings, electric heater humidifiers  present you with all the benefits of warm mist humidifiers.

10. Immersed Electrode Humidifiers

The final warm mist humidifier I came across is the immersed electrode humidifier. The way it works is fundamentally the same as your gas fired and immersed heater humidifier. It boils water in a tank to produce steam which is released through a steam outlet pipe into your ducting and thereafter into your building.

The difference however lies in how it boils water to produce steam. Instead of heat the electrode humidifier uses electricity flowing through streams of water to create steam. 

Electric current produced by a set of electrodes immersed in a replaceable tank called a boiling cylinder is carried through the water using the conductive properties of water. Then through a process called the Joule effect the electric current heats up the water to produce steam.

This entire process relies on the conductivity properties of water and so you can only use tap water for it to work. This is because tap water contains all the salts and minerals that give water its conductivity properties. So there is no need to treat your water with this type of humidifier.

However, this means you have no choice but to let minerals build up in your tank and this is where the replaceable boiling cylinder tank comes into play. Over time your electrodes get so covered up in limescale they become ineffective and a sensor on your humidifier indicates that it’s time for you to replace your boiling cylinder.

Normally you will need to replace your boiling cylinder after every 3 to 6 months of regular use depending largely on the quality of water you use. A lot of people go for the immersed electrode humidifier because it’s quite  inexpensive compared to all warm mist humidifiers.

But be careful, you actually end up forking out a lot of money replacing boiling cylinders. Kind of like buying an inkjet printer. It’s cheap but you pay a fortune for ink.

In terms of energy consumption, this type of humidifier consumes as much as your electric heater humidifier and so you should expect a high energy utility bill if you get one of these. The other downside of the electrode humidifier is that it provides the least consistent humidification compared to other humidifiers. 

When you set your desired humidity level it’s always off  by +/- 5% relative humidity compared to +/- 1% to 2% from other types of warm mist humidifiers. Despite these issues, you will still enjoy the benefits of a warm mist humidifier with an immersed electrode whole house humidifier. 

On this note I can say I have now shown you all the different types of humidifiers you are likely to find. Well, at least the main types that are available on the market. If there are any that I missed, please do mention them in the comments below and I will see about adding them to my list here.

About the Author


Jean is a research economist by profession and he runs Fresh Air Genie. He is enthusiastic about maintaining good air quality at home and on the go and he shares his knowledge about this here at Fresh Air Genie.


  1. Thank you very much for sharing this information.

    I need a humidifier and did not know how to choose.

    This is very helpful.

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