We use runtime verification (RV) to check various properties in a smart apartment. The properties can be broken down into three types: behavioral correctness of the apartment sensors, detection of specific user activities (known as activities of daily living), and composition of properties of the previous types. The context of the smart apartment provides us with a complex system with a large number of components with two different hierarchies to group properties and sensors: geographically within the same room, floor or globally in the apartment, and logically following the different types of properties. We leverage a recent approach to decentralized RV of decentralized specifications, where monitors have their own specifications and communicate together to verify more general specifications. This allows us to re-use specifications, and combine them to: (1) scale beyond existing centralized RV techniques, and (2) greatly reduce computation and communication costs.Sensors and actuators are used to create "smart" environments which track the data across sensors and humanmachine interaction. One particular area of interest consists of homes (or apartments) equipped with a myriad of sensors and actuators, called smart homes [16]. Smart homes are capable of providing added services to users. These services rely on detecting the user behavior and the context of such activities [11], typically detecting activities of daily living (ADL) [41,13] from sensor information. Detecting ADL allows to optimize resource consumption (such as electricity [1]), improve the quality of life for the elderly [37] and users suffering from mild impairment [42].Relying on information from multiple sources and observing behavior is not just constrained to activities. It is also used with techniques that verify the correct behavior of systems. Runtime Verification (RV) [30,35,24,6] is a lightweight formal method which consists in verifying that a run of a system is correct wrt a specification. The specification formalizes the behavior of the system typically in logics (such as variants of Linear Temporal Logic, LTL [39]) or finite-state machines. Based on the provided specification, monitors are automatically synthesized to run alongside the system and verify whether or not the system execution complies with the specification. RV techniques have been used for instance in the context of automotive [15] and medical [36] systems. In both cases, RV is used to verify communication patterns between components and their adherence to the architecture and their formal specifications.While RV can be used to check that the devices in a smart home are performing as expected, we believe it can be extended to monitor ADL properties, and complex behavior on the activities themselves. We identify three classes of properties for applying RV to a smart home. The first class pertains to the system behavior. These properties are used to check the correct behavior of the sensors, and detect faulty sensors. Ensuring that the system is behaving correctly is what i...