## 3 Use Case: Indoor Ventilation Monitoring  
In this work, we demonstrate our approach on an indoor ventilation dataset provided by Renson. Renson is a Belgian company that produces ventilation and shading products, including the Healthbox 3.0 ventilation unit ([[https://www.renson.eu/gd-gb/productenzoeken/ventilatie/mechanische-ventilatie/units/healthbox-3-0](https://www.renson.eu/gd-gb/productenzoeken/ventilatie/mechanische-ventilatie/units/healthbox-3-0)]([https://www.renson.eu/gd-gb/productenzoeken/ventilatie/mechanische-ventilatie/units/healthbox-3-0](https://www.renson.eu/gd-gb/productenzoeken/ventilatie/mechanische-ventilatie/units/healthbox-3-0)), accessed on 13 August 2021). When installed in a domestic environment, ventilation shafts connect the unit to nearby rooms. The shaft connector contains a valve to regulate airflow and is equipped with sensors that measure various air quality metrics such as humidity, CO2 or VOC (volatile organic compounds, i.e., odours). Using these sensors, the unit estimates the air quality and regulates the airflow by positioning the valves. The air quality and operating metrics of the healthbox are also sent to cloud infrastructure, provided customers agreed to this. This allows Renson to remotely monitor the performance of the Healthboxes, so they can predict when maintenance will be required. Additionally, this allows customers to monitor and control their indoor air quality through a smartphone app. The Renson dataset used in this work was captured from a Healthbox 3.0 installed in a real house with two ventilated rooms: a bathroom and bedroom. The data contains time series for the following sensor metrics: temperature, CO2, absolute and relative humidity and VOC (bathroom only). The data were sampled at 30 s intervals and was collected for 94 days. During the first 3 days, the house was not yet in use; during the next 14 days, the house was used normally; and during the remaining 77 days, the bathroom door was kept open so temperature/humidity/VOC was easily transferred between both rooms. Figure 1 displays the absolute humidity signals present in the dataset. Large spikes in the humidity signal of the bathroom (top of the figure) are attributed to showers. Smaller increases in the humidity signal of the bedroom (bottom of the figure) often occur after a shower and capture the spreading of humidity in the bedroom when the bathroom door is opened, a so-called shower echo effect. Humidity spikes do not occur at the start of the dataset, since the house was not in use during the first three days. Please note that variance in the indoor humidity signals is also influenced by outside weather conditions. Zero values in the signals indicate missing values due to data transmission failures. Renson's smartphone app for customers overlays air quality time series data with event markers to provide insights about changes in air quality and to explain ventilation boosts taken by the Healthbox. Renson is continuously expanding the set of detectors to display more useful event markers, however, in this paper, we focus on the interplay of different detectors rather than detecting as many events as possible. Therefore, in this paper, the detected events are limited to the following humidity related events: showers (large humidity spikes occurring in the bathroom), echo effects of showers (smaller humidity increases in rooms near the bathroom after a shower) and humid weather (high humidity caused by the outside weather when doors or windows are left open). While relevant events have a limited occurrence frequency, the sheer volume of the data does make manual labeling a challenging job. Data-driven methods can be used to bootstrap the labeling process by isolating candidate relevant events. However, not all candidate events found in this manner will be correct. Luckily, asking for customer feedback at this point is straightforward, by presenting the suggested events. Customers may notice mislabeled candidate events, incorrect candidate events or even events that were not suggested.