Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
A humidifier that is not cleaned regularly can aerosolize bacteria, fungi and mineral dust into the air. This procedure covers the cleaning interval, cleaning method, disinfection, and water selection to keep your humidifier safe and effective.
Necessary equipment
| Item | Note |
|---|---|
| brush or soft-bristled cleaning brush | Use this for the interior tank surfaces |
| cloth or soft sponge | Use this to wipe and dry surfaces |
| tap water material | Use this to rinse only |
| distilled water or demineralized water material | Use this to fill the humidifier tank |
| hydrogen peroxide solution (3%) material | Only if your manufacturer approves it. Follow your appliance manual. |
Specifications
Source: Use and Care of Home Humidifiers · tier 1 · accessed 2026-08-03
Source: Care of Room Humidifiers · tier 1 · accessed 2026-08-03
Source: Care of Room Humidifiers · tier 1 · accessed 2026-08-03
Source: Use and Care of Home Humidifiers · tier 1 · accessed 2026-08-03
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
Preparation
UNPLUG THE HUMIDIFIER BEFORE YOU CLEAN IT.
Water and electricity cause shock. Shock causes injury or death.
- Unplug the humidifier from the wall outlet.Report a problem with step 1, Preparation
- Empty the tank into a sink.Report a problem with step 2, Preparation
Clean the tank
DO NOT SKIP CLEANING.
A dirty humidifier aerosolizes bacteria and fungi. DO NOT BREATHE this mist. It causes respiratory illness and lung infection.
- Use a soft brush to scrub all tank interior surfaces.Report a problem with step 1, Clean the tank
- Rinse the tank. Use several changes of tap water.Report a problem with step 2, Clean the tank
- Clean removable parts as your manual directs.Report a problem with step 3, Clean the tank
- Dry all interior surfaces with a clean cloth.Report a problem with step 4, Clean the tank
Disinfect if needed
- Read your humidifier manual for approved disinfection methods.Report a problem with step 1, Disinfect if needed
- If your manual approves hydrogen peroxide, apply a 3% solution to tank surfaces.Report a problem with step 2, Disinfect if needed
- Rinse thoroughly. Use several changes of tap water to remove all disinfectant.Report a problem with step 3, Disinfect if needed
- Allow all parts to air dry completely before you reassemble the humidifier.Report a problem with step 4, Disinfect if needed
Choose and fill with water
ULTRASONIC HUMIDIFIERS DISPERSE MINERALS.
Tap water minerals become white dust on surfaces. SELECT distilled or demineralized water.
- Choose distilled water or demineralized water for your humidifier tank.Report a problem with step 1, Choose and fill with water
- Alternatively, use water that you boiled and cooled.Report a problem with step 2, Choose and fill with water
- Fill the tank with your chosen water.Report a problem with step 3, Choose and fill with water
- Reassemble the humidifier.Report a problem with step 4, Choose and fill with water
Operation and maintenance
- Plug the humidifier into the wall outlet.Report a problem with step 1, Operation and maintenance
- Empty the tank and refill it daily.Report a problem with step 2, Operation and maintenance
- Clean and disinfect the complete humidifier every three days during use.Report a problem with step 3, Operation and maintenance
- Maintain indoor humidity at 30 to 50 percent relative humidity.Report a problem with step 4, Operation and maintenance
- At the end of the season, drain the tank completely.Report a problem with step 5, Operation and maintenance
- Complete cleaning and disinfection of all parts before you store the humidifier.Report a problem with step 6, Operation and maintenance
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- humidifier
- Also called: no common alternatives
- ultrasonic humidifier
- Also called: no common alternatives
- distilled water
- Also called: no common alternatives
- mineral dust
- Also called: no common alternatives
When to use a professional
Do not force scale removal. Call a technician if the humidifier does not work after you clean it.
Common questions
Why does my humidifier create white dust?
Ultrasonic and impeller humidifiers disperse minerals dissolved in tap water as aerosolized white dust. This is especially noticeable with hard water. Use distilled, demineralized or boiled and cooled water instead to prevent this. The white dust itself is not harmful but can settle on furniture and surfaces.
Can I use tap water in my humidifier?
Tap water is acceptable for rinsing during cleaning, but distilled or demineralized water is preferred for filling. Tap water contains minerals that create scale buildup inside the tank and may aerosolize as white dust, especially in ultrasonic units. Check your manufacturer's manual for specific recommendations for your model.
What should I use to disinfect my humidifier?
The U.S. Environmental Protection Agency recommends a 3% hydrogen peroxide solution when the manufacturer provides no guidance. However, always follow your appliance manual first, as some humidifiers have specific requirements or restrictions on what cleaning products may touch their materials. After disinfection, rinse very thoroughly with tap water to remove all chemical residue before use.
How often should I clean my humidifier?
Empty and refill the tank daily, even if you do not run the humidifier continuously. Perform a thorough cleaning with a brush to remove scale and deposits every three days during active use. At the end of the heating season, clean and disinfect the entire unit before storage to prevent mold growth.
What humidity level should I maintain?
Indoor humidity should stay between 30 and 50 percent relative humidity if possible. Humidity above 50 percent allows moisture to build up on windows, walls and surfaces, where bacteria and fungi settle and grow. Most humidifiers have a humidity setting; adjust it according to your comfort and these guidelines.
Can dirty humidifiers make me sick?
Yes. A humidifier that is not cleaned regularly can aerosolize bacteria and fungi that have grown in the tank. Breathing this mist causes respiratory symptoms ranging from mild irritation to serious lung infection. Regular cleaning and use of clean water are the best ways to prevent this.
Related procedures
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1Use and Care of Home Humidifiers
- Tier 1Care of Room Humidifiers
- Tier 1Preventing Waterborne Germs at Home
- Tier 1Indoor Air Quality (IAQ) Use and Care of Home Humidifiers
Revision history
Current version 1 · updated 2026-08-03 · next review due 2027-08-03
- v · 2026-08-03
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.