Humidity indicator

A humidity indicator is a moisture-sensitive chemical that changes color when the indicated relative humidity is exceeded.

Humidity and hygrometry
Specific concepts
Absolute / Specific / Relative Dew point (depression) Psychrometrics
General concepts
Air Concentration Density Dew Evaporation Humidity buffering (Atm.) Pressure Liquid water Avogadro's law Nucleation Thermodynamic equilibrium
Measures and Instruments
Heat index Sat. vap. density Mixing ratio Water activity H. indicator card Hygrometer Dry/Wet-bulb temperature

Chemicals

Some chemicals are:

• cobalt(II) chloride (toxic) (blue to pink)
• copper(II) chloride (toxic) (yellow to blue)

Humidity indicator on the lithium-ion battery of an mobile phone
top: before wetting
bottom: after wetting
(battery model: Samsung AB653039)

See also

• Moisture analysis
• Humidity indicator card
• Desiccant