We have prepared composite samples of citrogypsum (calcium sulfate) dihydrate (CaSO4⋅2H2O) doped with copper sulfate (CuSO4⋅5H2O). The morphology of the microsection surface and the energy dispersive X-ray spectrum (EDX) of the sample were examined. The conductivity of the samples was studied by impedance spectroscopy. To measure the conductivity, an RLC AM-3026 AKTAKOM meter was used in the frequency range of 200 Hz - 5 MHz with an alternating signal amplitude of 1 V without DC polarization. The measurements were carried out at a constant temperature of 28 °C and relative humidity in the range from 30 to 90%. The frequency dependences of complex resistance and relative permittivity on relative humidity, total complex, active and reactive resistances are measured. We demonstrated the possibility of practical application of (CaSO4⋅2H2O)0.975-(CuSO4⋅5H2O)0.025 as a new air humidity sensor material. The new air humidity sensor material was obtained from a waste of the citric acid production.