A mercury monitor including a sample input unit, a thermal atomizer, an analytical cell capable to be heated, a gas collector unit, and a sucking out pump; wherein the analytical cell comprises: a body which is elongated along a longitudinal direction and includes a first butt end and a second butt end, two windows, wherein a first window is adjacent to the first butt end and a second window is adjacent to the second butt end and the windows are transparent for resonant radiation of mercury, wherein at least through one of the windows the analytical cell is optically coupled with an atomic absorption spectrometer, at least one input gas port located in central part of the analytical cell and at least two output gas ports, wherein a first output gas port is installed between the first window and the input gas port, closer to the first window, and a second output gas port is installed between the second window and the input gas port, closer to the second window, wherein the output gas ports are connected to a first side of the gas collector unit and the sucking out pump is connected to a second side of the gas collector unit and is adapted to create a cell pressure being lower than atmospheric pressure, wherein the sample input unit is coupled with an injecting pump capable to introduce an analyzed sample into the thermal atomizer, wherein a first end of the thermal atomizer is hermetically attached to the sample input unit and a second end of the thermal atomizer is hermetically attached to the input gas port of the analytical cell; the analytical cell has openings through which air can come into an interior area of the analytical cell to form a protective air stream between the windows and hot gas to be analysed, wherein a first opening is located between the first window and the first output gas port and a second opening is located between the second window and the second output gas port. a body which is elongated along a longitudinal direction and includes a first butt end and a second butt end, two windows, wherein a first window is adjacent to the first butt end and a second window is adjacent to the second butt end and the windows are transparent for resonant radiation of mercury, wherein at least through one of the windows the analytical cell is optically coupled with an atomic absorption spectrometer, at least one input gas port located in central part of the analytical cell and at least two output gas ports, wherein a first output gas port is installed between the first window and the input gas port, closer to the first window, and a second output gas port is installed between the second window and the input gas port, closer to the second window, wherein the output gas ports are connected to a first side of the gas collector unit and the sucking out pump is connected to a second side of the gas collector unit and is adapted to create a cell pressure being lower than atmospheric pressure, wherein the sample input unit is coupled with an injecting pump capable to introduce an analyzed sample into the thermal atomizer, wherein a first end of the thermal atomizer is hermetically attached to the sample input unit and a second end of the thermal atomizer is hermetically attached to the input gas port of the analytical cell; the analytical cell has openings through which air can come into an interior area of the analytical cell to form a protective air stream between the windows and hot gas to be analysed, wherein a first opening is located between the first window and the first output gas port and a second opening is located between the second window and the second output gas port.