A tritium monitor based on plastic scintillation sheets is described. The sensitive volume of the scintillation chamber is 0.95 l. The chamber with coincidence electronics has a discrimination capability and permits to detect tritium in the presence of other radionuclides and external gamma-radiation. The monitor characteristics obtained with tritiated air are presented. The monitor sensitivity for tritium in air is 5.6 cpm for each kBq·m−3. The monitoring of tritium in air and water is possible using the instrument described.