Abstract: A gas sensing device has a power source, data processing means and a memory for storing sampling configuration data and sensed data. Sensing means samples ambient gas adjacent the device according to first sampling configuration data and outputs sensed gas concentration data and sensed gas flow data. A telemetry module communicates the sensed data to a remote terminal and receives second sampling configuration data from the remote terminal for updating the first sampling configuration data. A gas monitoring system comprises the terminal and at least one gas sensing device remote from the terminal. 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.