This international standard specifies definitions and methods to determine performance characteristics of automatic air quality measuring systems. This is done for most performance characteristics under steady laboratory conditions so as to have available data on clearly defined characteristics, based on specified conditions that can be adjusted and maintained in laboratory. This is also done under field conditions for a few performance characteristics for which field testing provide relevant additional information. In this International Standard, automatic air quality measuring systems are considered as "black boxes" operated according to specified procedures as described in the terms of reference given by the client to the laboratory performing the tests aiming at determining performance characteristics selected by the client.