The document describes the basic principles of the processes in landfill sites and the factors which affect landfill gas formation and composition. Additionally, it details the essential features of landfill gas measurements and measurement planning as well as the necessary sampling and measurement methods for the various measurement objectives. Target compounds are primarily the permanent gases carbon dioxide (CO2), methane (CH4), oxygen (O2) und nitrogen (N2) which constitute the main components of landfill gas. Reference is made to minor components such as hydrogen sulphide (H2S) and ammonia (NH3) and trace components such as LCHC, BTEX and organic silicon compounds.