Electrical wiring accessory having an indicator for the ambient air quality, • having a flush-mounted accessory frame, a central sensor part and a covering frame, • wherein the flush-mounted accessory frame has a power supply unit whose primary side is connectable via a supply connection to an AC power supply and whose secondary side is connectable via a contact-connection to the central sensor part, • wherein the central sensor part has ventilation slots for a through-flow of ambient air, • wherein the central sensor part has a CO2-determining ambient air quality sensor, a colour-display light-emitting indicator and a control unit actuating the latter, and these structural components are powerable by the power supply unit via the contact-connection, • wherein the ambient air quality sensor detects not only CO2 but also odorous gases and instances of outgassing and calculates a CO2-equivalent signal from the measured gases and the volumes thereof. • wherein the control unit evaluates the sensor signal of the ambient air quality sensor by means of a sensor signal evaluation unit and actuates the colour-display light-emitting indicator on the basis of the result of this evaluation using a threshold value logic unit and by means of a colour-display actuating unit, • wherein the central sensor part has a touch area that applies pressure to a switching element connectable via the contact-connection to a load switching element, arranged in the flush-mounted accessory frame, that uses a switching output to switch an electrical load, a room illumination, on/off, and • the touch area of the central sensor part applies pressure to a further switching element, which is connectable via the contact-connection to a further load switching element, arranged in the flush-mounted accessory frame, that uses a further switching output to switch a further electrical load, a fan, on/off. • having a flush-mounted accessory frame, a central sensor part and a covering frame, • wherein the flush-mounted accessory frame has a power supply unit whose primary side is connectable via a supply connection to an AC power supply and whose secondary side is connectable via a contact-connection to the central sensor part, • wherein the central sensor part has ventilation slots for a through-flow of ambient air, • wherein the central sensor part has a CO2-determining ambient air quality sensor, a colour-display light-emitting indicator and a control unit actuating the latter, and these structural components are powerable by the power supply unit via the contact-connection, • wherein the ambient air quality sensor detects not only CO2 but also odorous gases and instances of outgassing and calculates a CO2-equivalent signal from the measured gases and the volumes thereof. • wherein the control unit evaluates the sensor signal of the ambient air quality sensor by means of a sensor signal evaluation unit and actuates the colour-display light-emitting indicator on the basis of the result of this evaluation using a threshold value logic unit and by means of a colour-display actuating unit, • wherein the central sensor part has a touch area that applies pressure to a switching element connectable via the contact-connection to a load switching element, arranged in the flush-mounted accessory frame, that uses a switching output to switch an electrical load, a room illumination, on/off, and • the touch area of the central sensor part applies pressure to a further switching element, which is connectable via the contact-connection to a further load switching element, arranged in the flush-mounted accessory frame, that uses a further switching output to switch a further electrical load, a fan, on/off.