Establishing Semantic Data Requirements for Defining a 3D Spatial Data Model for Indoor Air Quality Monitoring Applications

Indoor air quality (IAQ) monitoring has become increasingly important due to its effects on occupant health, comfort, productivity, and overall indoor environmental quality. Despite advances in sensing technologies and environmental monitoring systems, there remains limited consensus on which parameters should be represented in a comprehensive monitoring framework. To address this gap, this study aims to establish semantic requirements for defining a 3D spatial data model for IAQ monitoring using the Delphi method. Candidate parameters were identified through a review of the literature on indoor environmental quality, environmental monitoring, building performance, and occupant well-being, and subsequently evaluated in a two-round Delphi study involving experts from academia, government, and industry. Consensus was assessed using predefined statistical criteria based on measures of central tendency, dispersion, and agreement. The Delphi process validated parameters grouped into five thematic categories, including physicochemical pollutant indicators, hygrothermal and comfort-related variables, spatial and operational factors, sensor and monitoring characteristics, and contextual and human-centered considerations. In addition to commonly monitored indicators such as carbon dioxide, particulate matter, temperature, and humidity, the results highlighted the importance of occupancy-related factors, ventilation characteristics, sensor metadata, structural ingress pathways, and contextual environmental influences for characterizing IAQ. The findings demonstrate that effective representation of IAQ extends beyond pollutant measurements alone and requires consideration of environmental, operational, spatial, and human-centered factors. The validated parameter set provides a structured, expert-informed foundation for future indoor environmental monitoring frameworks and for developing 3D spatial data models for IAQ monitoring applications.