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Humidity sensor recipe

A basement or a bathroom that stays damp long enough for mold, and the slow leak that keeps a room damp.

A basement or a bathroom that stays damp long enough for mold, and the slow leak that keeps a room damp. At chest height in the room, out of the shower's spray and away from a dehumidifier's outlet. In Home Assistant it shows up as a sensor, device class humidity. When the room stays above 60 percent humidity for 60 minutes, tell you to look for a leak. EPA says to keep indoor humidity below 60 percent. The recipe waits an hour above that line, because a shower or a mopped floor passes and a damp room does not. EPA's ideal is between 30 and 50 percent, and it says to dry anything wet within 24 to 48 hours to prevent mold.

What it catches

A basement or a bathroom that stays damp long enough for mold, and the slow leak that keeps a room damp.

Where it goes

At chest height in the room, out of the shower's spray and away from a dehumidifier's outlet.

How it shows up in Home Assistant

As a sensor, device class humidity. Battery sensors usually talk over a low-power mesh radio (Zigbee, Z-Wave or Thread) to a hub or a USB stick on the Home Assistant machine.

Why the recipe looks like this

EPA says to keep indoor humidity below 60 percent. The recipe waits an hour above that line, because a shower or a mopped floor passes and a damp room does not. EPA's ideal is between 30 and 50 percent, and it says to dry anything wet within 24 to 48 hours to prevent mold.

Write it for your sensor

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SensorRadioAutomationYou

Humidity sensor. When the room stays above 60 percent humidity for 60 minutes, tell you to look for a leak.

percent
minutes

automations.yaml

Download
- alias: "Damp: above 60 percent humidity"
  mode: single
  triggers:
    - trigger: numeric_state
      entity_id: sensor.basement_humidity
      above: 60
      for:
        minutes: 60
  actions:
    - action: notify.mobile_app_your_phone
      data:
        title: "Damp room"
        message: "{{ trigger.to_state.name }} has been at {{ trigger.to_state.state }} percent. Look for a leak and run a dehumidifier."

Rename the entities to your own, then paste. Syntax: Home Assistant: Automation triggers.

Sources

  1. Home Assistant: Sensor (device classes temperature, humidity, power, battery) Home Assistant
  2. Home Assistant: Numeric state trigger Home Assistant
  3. EPA: A brief guide to mold, moisture and your home U.S. Environmental Protection Agency

Drafted with a language model on October 26, 2026 from the sources listed above. Every recipe on the page is written by the site's own code and parsed by a test. The editor samples pages after they publish; nothing here is advice from a licensed electrician or plumber.

Found an error? See Corrections.

Humidity sensor recipe | Sensor House