How Often Do You Need to Change A Humidifier Filter?


You have a good humidifier, but you notice that the mist coming out of it seems to be a bit dirty and smelly. This might even affect your breathing.

Humidifiers usually come with filters, and these need to be either changed or cleaned on a regular basis. We want to take a look at the various types of humidifiers and how often their filters need to be changed.

Central Humidifiers or Whole-House Humidifiers

In case you are wondering what a central humidifier is, these are often very large humidifiers that are directly connected to the furnace and use the heating ducts and cold air returns to disperse the moisture along with the heat from the furnace.

The point of these is to heat water and to release steam throughout the house by using your heating system, the furnace, to accomplish this task. These are not portable and are built directly into your home. Although they are not portable, if you are looking to humidify a whole home, these tend to be best.

In terms of changing the filters on these, it is recommended to change them around once per month. Bacteria, mold, and other organisms can easily build up on these, and then be dispersed into your whole home. It’s therefore essential to change the filter often.

It will depend on your climate and air quality in the home, but one change every 1 to 2 months is recommended. There are also central/whole house humidifiers which feature washable filters. These can come in handy. Although the initial cost will be higher with a washable filter, you’ll save money on filter replacements in the long run.


Evaporator humidifiers work by using a filter that is wet with water, and air fans which then evaporate and blow that filter based moisture into the air. These tend to be very small, ideal for single rooms, they are silent, and generally energy efficient as well.

Because the moisture is being blown straight from the filter into the room, keeping the filter clean is essential.

If you use the evaporator on a daily basis, changing the filter every 1 to 2 months is recommended. However, because they don’t see as much action as something like a central humidifier, most people can get away with changing the filter once every 3 to 4 months.

Ultrasonic Humidifiers

Ultrasonic humidifiers use special vibrating plates which move super quickly. These vibrations cause water to be turned into airborne mist. These can come in both cool mist and warm mist options. These tend to be fairly technologically advanced and they can come in all sorts of sizes.

The filters on the devices should be changed every 3 months. If you use your ultrasonic humidifier on a daily basis, you might want to consider changing the filter every 6 to 8 weeks. The warm mist ultrasonic humidifiers will require less frequent filter changes as hot steam is much more effective than cold mist at killing mold and bacteria.

Be aware that some ultrasonic humidifiers do not have filters at all. Whether or not it has a filter is going to depend on the specific model. Of course, if you get one without a filter, then there is nothing to be changed.


Although impeller humidifiers are relatively new, they are quickly becoming one of the most popular types because they tend to be very affordable, they are portable, and ideal for single rooms. They also release quite a bit of humidity too.

These function by using two impellers which rotate against each other. This creates a lot of friction and heat, which ends up causing water to evaporate and turn into mist which is then dispensed throughout a room. These have a tendency to suffer from fast dirt and deposit buildups.

Although the filters usually do not need to be changed, they should be washed with a water and vinegar solution after every use.

Cool Mist

Cool mist humidifiers work by either evaporating the water using a fan or by using ultrasonic vibrations to create mist. These do work very well, but beware that because they do not use heat, they can suffer from mold buildups, as well as the buildup of other contaminants.

With daily use, you will want to change the filter on your cool mist humidifier every 2 to 4 months. The filters on evaporative cool mist humidifiers generally need to be changed more often than the filters in ultrasonic cool mist humidifiers.

Warm/Hot Steam Humidifiers

Hot steam or warm mist humidifiers rarely come with filters at all. The reason for this is because the process of heating the water up to create steam is usually enough to kill all bacteria, mold, and other contaminants present in the water.

If your hot steam or warm mist humidifier does come with a filter, changing it every 4 to 6 months will do just fine. Warm mist humidifiers, if they come with filters, require the filter to be changed more often than hot steam humidifiers. The hotter they operate, the less likely they are to require filtration and filter changes.


Whatever type of humidifier you have, unless it is a filterless hot steam humidifier, you will need to change the filter on a regular basis, or at the very least, clean it regularly. You don’t want mold, bacteria, and other airborne particles being dispersed into your home, so maintaining a clean filter is essential to your health.


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