Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for monitoring air quality with multiple sensing devices. The methods, systems, and apparatus include actions of: obtaining first sensor data from a sensor that is not an air quality sensor, determining that the first sensor data satisfy a first air quality criterion, in response to determining that the first sensor data satisfy the first air quality criterion, obtaining second sensor data from an air quality sensor, determining that the second sensor data satisfy a second air quality criterion, and based on a determination that the second sensor data satisfy the second air quality criterion, activating an air quality device.

Abstract: Example techniques relate to playback queue subscriptions. An example implementation involves a computing system receiving, from a first computing device associated with a first user account, an instruction to enable subscription to a first playback queue associated with a first media playback system. In response to the instruction, the computing system enables second user accounts to subscribe to the first playback queue. The second user accounts are registered with respective second media playback systems in respective second household. The computing system receives, from a particular second media playback system, a request to subscribe to the first playback queue; and in response, sends one or more messages that update a control interface of the first control device to display a subscriber indication and (ii) sends one or more messages that populate a second playback queue of the particular second media playback system with audio tracks of the first playback queue.