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You may have been seeing a few specks of white dust coming from your heating system, and now you are looking for a solution. This white dust is produced by ultrasonic and impeller heating systems and is a result of hard water minerals. luckily, it’s not dangerous and can be easily cleaned off and prevented.
White dust from heating systems is caused by the mineral content found in the hard water that goes into Impeller and Ultrasonic humidifiers and is sprayed into the house as vapor. Clean off the dust and prevent it by using soft water, a demineralization cartridge, and a warm/cool mist humidifier.

What is the white dust coming out of my heating system?
The white dust is a combination of dissolved minerals and mist that has dried up. Both of these things come from the water you feed into the heating system. Humidifier white dust is common with ultrasonic and impeller humidifiers and when you use hard water to humidify the house. It’s different from the black dust around air vents which can be soot, mold, or dust from outdoors.
What causes white dust from heating systems?
There are two main causes of the white dust as follows:
1. Use hard water in a humidifier
The white dust is mainly caused by the contact between hard water and the heating system’s humidifier. Although not all heating systems have humidifiers, a huge number of them do. Some examples of heating systems with humidifiers include ultrasonic and impeller heating systems. Both of them produce white dust/particles when used with hard water.
A humidifier within a heating system is used to add moisture to the air. Moist air is good as it retains heat better than dry air. As a result, the house remains warm.
For this heating system to work, one needs to add water. In most households, you will find that the residents add hard water to the system. Hard water contains a lot of minerals that contribute to the production of white dust in your house.
How Does This Happen? (Explanation)
When hard water is fed into the heating system, it undergoes a steaming process and turns into steam (vapor). It’s then spewed out through the humidifier in the form of mist. Since the mist is a product of the hard water that was fed into the system, it contains the same minerals.
When the mist is released into your home’s environment, it settles on various surfaces like floors and furniture. The mist then dries up leaving behind the minerals that form whitish particles. Now, this is the white dust you see whenever you walk into a room that has a heating system. Ultrasonic humidifier white dust is quite common in homes that use hard water for humidification.
2. Faulty furnace
There are instances where one may use soft water and still end up with white dust even when soft water has little or no minerals. When this happens, there is a very high chance that your heating system is faulty.
Given that furnace exhaust is acidic, it will create a white powder if it reacts with the zinc in galvanized steel. It’ll form both zinc hydroxide and zinc oxide with the latter being the white powder on surfaces. It’s the same thing that happens with the terminals of a car battery.
If you ever find yourself in such a situation, the best thing to do is to call in the experts. This is because they are the ones who are in a better position to run a diagnosis on your system and fix it.
How to Get Rid of White Dust from Heating Systems

Although there are differences between white dust and “normal dust,” the process of eliminating both of them is similar. Here are a few ways of getting rid of white dust from heating systems:
1. Sweep off the dust
You can use a broom and a dustpan to get rid of white dust in your home. Just choose a starting point which should be inside the house then sweep towards the outside. Thereafter, collect the dust using a dustpan and discard it.
2. Use a vacuum cleaner
Using a vacuum cleaner will suck in the dust and deposit it in the dust bag inside it. You then empty it in the trash bin or other appropriate location. For the best results, dust before vacuuming the white dust off surfaces.
3. Dust using a damp cloth
You can also wipe the surface using a wet cloth. This is effective as the white dust will stick onto the cloth, and you can then get rid of it.
If all of these fixes fail, call in an HVAC expert to remedy the situation. It could be a faulty HVAC system.
How to prevent white dust in a heating system
It is good to put in place measures to prevent/stop the production of these white particles in your home. There are a lot of reasons why this is necessary, and some of them include:
- They are harmful to the human body, especially when inhaled by infants and young children. They may also cause health complications for people with asthma, allergies, and sinuses.
- The white dust makes the house look dirty and messy.
Prevent white dust from heating systems as follows:
1. Fill your heating system with soft water
The first thing you can do is fill the heating system with soft water instead of tap water. One way of acquiring this kind of water is by “softening” the tap water using a distillation chamber.
Distillation is a very effective way of getting soft water. This is because it evaporates the water and then collects it in another chamber/container. As it does this, ions/minerals that previously made the water hard are left behind. Once you use this water in your heating system, you will certainly enjoy staying in a warm and humid house with no white dust.
Another way of softening hard water is by using an ion-exchange filter. An ion exchange filter softens water by filtering the minerals out. As a result, you are left with mineral-free water (soft water).
2. Installing a demineralization cartridge
Installing demineralization cartridges can also help in preventing the production of white dust. This is because they trap the minerals before becoming airborne in the household. They can partially or totally eliminate the white dust.
3. Use a portable warm or cool mist humidifier
You can also invest in a portable warm or cool mist humidifier. With this, having white dust in your home will be a thing of the past since they don’t humidify the house in the same way as ultrasonic humidifiers. You can also consider a choice between ultrasonic and evaporative humidifiers since the latter produce less white dust.
White dust is mainly formed when the minerals in hard water come into contact with the humidifier of a heating system and are spewed out as mist. Although many people are not aware, white dust is actually harmful, especially to young ones and people with allergies. With the fixes and preventive measures discussed here, you can be sure of getting rid of white dust in your home.

HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.