A gas sensing device to measure ambient ground gas, comprising a power source ; data processing means ; memory means operably interfaced with the data processing means and for storing sampling configuration data and sensed data ; sensing means operably interfaced with the power source and the data processing means, wherein the sensing means is adapted to sample ambient ground gas adjacent the device according to first sampling configuration data and to output at least_sensed gas concentration data and sensed gas flow data ; and a telemetry module operably interfaced with the power source and the data processing means, wherein the telemetry module is adapted to establish a network connection with a remote terminal, communicate the sensed data to the remote terminal and receive second sampling configuration data from the remote terminal for updating the first sampling configuration data; characterised in that the sampling configuration data comprises data representative of a frequency and duration of gas flow measurement, data representative of a frequency and duration of gas concentration measurement, and data representative of an offset time corresponding to a time interval between a gas flow measurement and a gas concentration measurement, wherein the sensing means comprises a gas concentration sensing module comprises a gas sampling circuit, extending between a first gas inlet and a first gas outlet and including a sensor chamber , a pump and a pressure gauge ; and a gas flow sensing module comprises a gas sampling circuit, extending between a second gas inlet and a second gas outlet and including a valve and a flow sensor . a power source ; data processing means ; memory means operably interfaced with the data processing means and for storing sampling configuration data and sensed data ; sensing means operably interfaced with the power source and the data processing means, wherein the sensing means is adapted to sample ambient ground gas adjacent the device according to first sampling configuration data and to output at least_sensed gas concentration data and sensed gas flow data ; and a telemetry module operably interfaced with the power source and the data processing means, wherein the telemetry module is adapted to establish a network connection with a remote terminal, communicate the sensed data to the remote terminal and receive second sampling configuration data from the remote terminal for updating the first sampling configuration data; characterised in that the sampling configuration data comprises data representative of a frequency and duration of gas flow measurement, data representative of a frequency and duration of gas concentration measurement, and data representative of an offset time corresponding to a time interval between a gas flow measurement and a gas concentration measurement, wherein the sensing means comprises a gas concentration sensing module comprises a gas sampling circuit, extending between a first gas inlet and a first gas outlet and including a sensor chamber , a pump and a pressure gauge ; and a gas flow sensing module comprises a gas sampling circuit, extending between a second gas inlet and a second gas outlet and including a valve and a flow sensor . <EOS>