Developing an Indoor Air Pollution Inventory Tool to Visualise Activity-based Indoor Concentrations of Pollutants and Their Emission Rates for the Wider Community.

Indoor air quality is key due to the amount of time people spend indoors (approximately 80–90 % of their lives). However, understanding how time and activity dependent sources, as well as built environment characteristics, influence pollutant emissions and distributions remains very limited. Addressing these challenges, InAPI — an Indoor Air Pollution Inventory tool — has been developed using data synthesised from a comprehensive review of 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). InAPI leverages this database to enable users to visualise indoor pollutant levels and emission characteristics across varied indoor settings. InAPI consolidates this evidence into a practical and easy-to-use tool which facilitates standardisation of IAQ measurement protocols and the creation of activity-based indoor emission inventories. By providing a robust platform for understanding indoor air pollutant dynamics, InAPI represents a significant step forward in advancing IAQ research given the transferability of the approach, supporting efforts to mitigate indoor air pollution with potential to inform policy initiatives. A key challenge to overcome is how to make this tool attractive and usable for non-experts and to ensure that the information is presented in a way that it can and will be used by policy makers and practitioners.