Table 5.

Classification of humidity-sensitive materials.

Classification	Characteristics	Examples
Electrolytes	Good humidity-sensitive response characteristics and simple preparation [1], absorbs water and can be diluted; if outflow occurs, humidity-sensing properties are damaged.	Polyacrylic acid (medical and health), polystyrene sulfonate
Polymer compounds	Wide range of materials, wide relative humidity range, low cost, rapid moisture-sensitive response, excellent heat resistance, and rapid humidity response; however, high resistance temperature coefficient, poor reproducibility and interchangeability, and low pollution tolerance.	Polyimide (plastic), hyperbranched quaternary ammonium salt (disinfectant and bactericide)
Porous metal oxides	Low density, high porosity, large specific surface area, and selective permeability to gas.	MeCr2O4-Bi2O3 systems, porous α-Fe2O3 nanospheres