Indoor Air Quality Modelling: Challenges and Opportunities

Indoor air quality (IAQ) has become a critical focus of research due to the substantial amount of time people spend indoors, where a significant proportion of air pollution exposure occurs. However, understanding how time and activity dependent sources, as well as built environment characteristics, influence pollutant emissions and distributions remains very limited.This presentation will provide an overview of recent developments on indoor air quality modelling outlining the latest capabilities of the tools initially developed in the MetOffice/Strategic Priorities Fund (SPF) project "Indoor Air Quality Emissions & Modelling System (IAQ-EMS)". Specific focus will be the opportunities and challenges associated with contrasting modelling approaches such as ChemFlow3D (Liu et al., 2025; doi.org/10.1063/5.0270416) with high spatial and temporal resolution and multi-box flexible (MBM-Flex) modelling which allows the incorporation of a wide range of chemical schemes and tracking concentration gradients across complex buildings and at the indoor-outdoor interface while assuming well-mixed conditions in each box. Development opportunities and use cases will also be discussed. We have also developed, InAPI — an Excel-based Indoor Air Pollution Inventory tool — using data synthesised from reviewing UK indoor air pollution research (Mazzeo et al., 2025; doi.org/10.5194/egusphere-2025-783). For the development of the InAPI tool, we have categorised existing literature by pollutant types, indoor environments, and activities, identifying significant knowledge gaps and offering an open-access database of typical pollutant concentrations and emission rates (Mazzeo et al., 2025; doi.org/10.1039/D4EA00121D). Despite the fragmented methodologies in historical IAQ research and the underrepresentation of key sources, pollutants, and environment-specific characteristics (in particular ventilation and occupant behaviour), InAPI consolidates this evidence into a practical and easy-to-use tool.By providing a robust platform for understanding indoor air pollutant dynamics, our work aims to advance IAQ research in the UK and beyond given the transferability of the approach, and thus support efforts to mitigate indoor air pollution and inform policy initiatives nationally and globally.