We discuss quality control of environmental measurement data. Typically, environmental data is used to compute some specific indicators based on models, historical data, and the most recent measurement data. For such a computation to produce reliable results, the data must be of sufficient quality. The reality is, however, that environmental measurement data has a huge variation in quality. Therefore, we study the use of quality flagging as a means to perform both real-time and off-line quality control of environmental measurement data. We propose the adoption of the quality flagging scheme introduced by the Nordic meteorological institutes. As the main contribution, we present both a uniform interpretation for the quality flag values and a scalable Enterprise Service Bus based architecture for implementing the quality flagging. We exemplify the use of the quality flagging and the architecture with a case study for monitoring of built environment.