All data files have the same format. MM is the two-digit GMT month when the air sample was collected. Missing values are denoted by 99. DD is the two-digit GMT day when the air sample was collected. Missing values are denoted by 99.
HR is the two-digit GMT hour when the air sample was collected.
Missing values are denoted by 99. MIN is the two-digit GMT minute when the air sample was collected. Missing values are denoted by 99. These identification numbers may be numeric, character, or alphanumeric with one to eight characters. Two flasks are connected in series, flushed with air, and then pressurized to 1.2-1.5 times ambient pressure.