This dataset represents hourly averaged measurements of 5 metal oxide chemical sensors embedded in an air quality chemical multisensor device. The certified analyzer was located on the field in a significantly polluted area, at road level, within an Italian city. Data were recorded from March 2004 to February 2005 (one year), representing the longest freely available recordings of on-field deployed air quality chemical sensor device responses (De Vitoet et al., 2008). Task: The dataset can be used to study causal discovery methods. Summary: Size of dataset: 9357 x 15 Task: Causal Discovery Problem Data Type: Mixed Data Dataset Scope: Standalone Dataset Ground Truth: Unknown Graph Temporal Structure: Time Series Data License: CC BY 4.0 (see https://archive.ics.uci.edu/dataset/360/air+quality) Missing Values: No Missing Values Missingness Statement: There are no missing values. Features: Date: (DD/MM/YYYY) Time: (HH.MM.SS) CO(GT): True hourly averaged concentration CO in mg/m^3 (reference analyzer) PT08.S1(CO): (tin oxide) hourly averaged sensor response (nominally CO targeted) NMHC(GT): True hourly averaged overall Non Metanic HydroCarbons concentration in microg/m^3 (reference analyzer) C6H6(GT): True hourly averaged Benzene concentration in microg/m^3 (reference analyzer) PT08.S2(NMHC): (titania) hourly averaged sensor response (nominally NMHC targeted) NOx(GT): True hourly averaged NOx concentration in ppb (reference analyzer) PT08.S3(NOx): (tungsten oxide) hourly averaged sensor response (nominally NOx targeted) NO2(GT): True hourly averaged NO2 concentration in microg/m^3 (reference analyzer) PT08.S4(NO2): (tungsten oxide) hourly averaged sensor response (nominally NO2 targeted) PT08.S5(O3): (indium oxide) hourly averaged sensor response (nominally O3 targeted) T: Temperature in °C RH: Relative Humidity (%) AH: Absolute Humidity Files: AirQuality.csv: dataset