This guideline deals with the assessment of technical density of flange connections for fluid and gaseous media for emission control requirements refering to the Technical Instructions on Air Quality Control TA Luft. The guideline is valid for metal flanges, e.g. materials refering to DIN EN 1092-1 to -4 from steel, cast iron, copper and aluminium up to a maximum operating temperature of 400 °C. It applies to flange connections for piping, machines and valves of all sectors of industry, especially to chemical, petrochemical and oil processing industry. The guideline does not apply to boltless pipe and flange connections and so called consolidated flange joints without seal or with liquid seals. The guideline has the objective to specify the state of the art of emission control for flange connections in the legal sense of the TA Luft and especially referring to TA Luft No. 126.96.36.199 in view of the requirements for technically tight flange connections. The required leak tightness classes for the design of a technically tight flange connection as required by TA Luft are defined. Components of the guideline are normative references that are necessary for the application of this guideline and the basis for design and calculation of flanged connections and instructions for assembling. Furthermore the guideline gives explanations for the selection of sealing constants as well as additional informations for the calculation of flange connections.