A method to release a confined stowage unit for unloading or physical inspection, said method comprising: A. an air sample analyser at a central location with multiple confined stowage units (100, 104) analysing a first air sample of said confined stowage unit and determining an inventory of gases present in said first air sample with their gas concentrations; B. a first generic sensor measuring at said central location a first generic sensor value for said first air sample, a generic sensor being a sensor providing a read-out value, named the generic sensor value, that is indicative for the presence of one or several compounds that are not necessarily dangerous, and that can be related to the concentration or evolution of the concentration of one or several toxic compounds in said inventory; characterised by C. a processor determining a safe generic sensor value from said gas concentrations in said inventory and said first generic sensor value, and producing a risk evaluation report for said confined stowage unit, said risk evaluation report comprising an aeration recommendation and said safe generic sensor value; D. a second generic sensor similar to said first generic sensor measuring at a decentralized location whereto said confined stowage unit is transported and where said confined stowage unit has been aired according to said aeration recommendation, a second generic sensor value for a second air sample of said confined stowage unit; E. comparing said second generic sensor value with said safe generic sensor value; and F. releasing said confined stowage unit for unloading or physical inspection if said second generic sensor value is below said safe generic sensor value. A. an air sample analyser at a central location with multiple confined stowage units (100, 104) analysing a first air sample of said confined stowage unit and determining an inventory of gases present in said first air sample with their gas concentrations; B. a first generic sensor measuring at said central location a first generic sensor value for said first air sample, a generic sensor being a sensor providing a read-out value, named the generic sensor value, that is indicative for the presence of one or several compounds that are not necessarily dangerous, and that can be related to the concentration or evolution of the concentration of one or several toxic compounds in said inventory; characterised by C. a processor determining a safe generic sensor value from said gas concentrations in said inventory and said first generic sensor value, and producing a risk evaluation report for said confined stowage unit, said risk evaluation report comprising an aeration recommendation and said safe generic sensor value; D. a second generic sensor similar to said first generic sensor measuring at a decentralized location whereto said confined stowage unit is transported and where said confined stowage unit has been aired according to said aeration recommendation, a second generic sensor value for a second air sample of said confined stowage unit; E. comparing said second generic sensor value with said safe generic sensor value; and F. releasing said confined stowage unit for unloading or physical inspection if said second generic sensor value is below said safe generic sensor value.