Indoor humidity levels, from the EPA
The ranges the EPA names, and how to check your room.
The upper limit
The EPA's humidifier guidance says: "Do not humidify to indoor relative humidity levels exceeding 50 percent." It says higher levels may encourage the growth of biological organisms in the home.
The range in the EPA mold guide
The EPA mold guide says to keep indoor humidity below 60 percent, "ideally between 30 and 50 percent" relative humidity.
How to measure it
The EPA says hygrometers, sold at hardware stores, can measure humidity. Some humidifiers have a built in humidistat you can set.
Signs of too much
The EPA says that if water condenses on windows, walls, or pictures, you should move the humidifier, lower its setting, or use it less. It says not to let the area around the humidifier get damp.
Why people use one
The EPA says humidifiers are "commonly used in homes to relieve the physical discomforts of dry nose, throat, lips, and skin," and that the added moisture helps with static and cracks in paint and furniture in winter. The EPA also says excess moisture "can encourage the growth of biological organisms in the home." We make no health claim for any product.
This is general information, not medical or purchasing advice.
Sources: EPA, Use and Care of Home Humidifiers; EPA, A Brief Guide to Mold, Moisture and Your Home.
FAQ
Next: room size
Measure the room, then read the rating.
