**5. Conclusions**

This paper (1) proposed a framework for an AQDSS and (2) developed an IoT application based on this framework. The feasibility of the IoT application in measuring PAPE was evaluated through a case study. In comparison to mobile sensors that were used in previous studies, this IoT application has higher scalability, because it involves minimal cost and intrusion to the individual. This pilot case study also presents evidence that PAPE can be estimated by employing indoor monitors and e-beacon technologies that have not been used previously in similar studies.

Using our proposed framework as a general guideline, the IoT application that we developed can be further extended to include prediction models that will allow an individual to make smart decisions when it comes to PAPE risk. Furthermore, PAPE data obtained from the application can be used in air quality policy development as well as in epidemiological studies to explore the correlations of PAPE with certain diseases.

We faced difficulties during the extraction and integration of data from multiple devices, which highlights the importance of choosing the right technologies to use when developing such IoT applications. There was an observed variance among the different devices, which can be attributed to device calibration and the measurement techniques used. Future research should, therefore, explore these issues and identify emerging technologies that permit seamless data integration and more accurate PAPE measurements.

**Author Contributions:** The conceptual framework was carried out by B.G. and J.O.-M., while implementation of software was carried out by B.G. Technical writing was carried out mainly by K.A.G.A. and S.S. Funding acquisition was done mainly by J.O.-M.

**Funding:** Financial support for this research was granted by China Scholarship Council and the European Commission through the EU funded project under the RFCS program with project number 793505 4.0 Lean system integrating workers and processes (WISEST).

**Acknowledgments:** The authors would like to acknowledge the City Hall of Madrid for the public data on air quality. Indeed, additional acknowledge is due to the Spanish Agencia Estatal de Investigacion, through the research project with code RTI2018-094614-B-I00 into the "Programa Estatal de I+D+i Orientada a los Retos de la Sociedad".

**Conflicts of Interest:** The authors declare no conflict of interest.
