In order to increase the reliability of detection of gaseous contamination in containers, gas (G) from the container is subject to several different methods of analysis (54a to 54d), each of which emits differing output signal courses (I.sub.1 to I.sub.4), depending on the contaminants and their concentration. A vector of the state vector type (P.sub.GAS) is formed with the output signals (I.sub.1 to I.sub.4) as a state variable and checked to see whether it defines a permissible or an unacceptable state of contamination (56). On the basis of this examination the decision is taken whether a container is acceptably or unacceptably contamined.