Air samples are collected from Arrival Heights for analysis of trace gas concentration and isotopic composition throughout the year. The high pressure samples that are collected from February through until August must be stored until they can be returned to New Zealand for analysis. The cylinders that are used are clean and dry so that the change in gas composition is kept to a minimum during the ... storage period. The production of 14CO can occur within the containers due to cosmic ray derived neutrons and 14N reacting to form 14C and hence 14CO. An experiment was undertaken that examined the in situ production by transporting cylinders with air of known composition between Christchurch and McMurdo during Ferbruary 2004 along with neutron dosimeters that operate in different energy ranges to determine the production rate of 14CO.