Background and Objectives:
Indoor air quality (IAQ) is a significant determinant of health and well-being. Most people spend 90% of their time inside, so maintaining a high level of IAQ is essential. As primary healthcare facilities serve large populations and have many employees, it is especially critical to characterise their IAQ. However, scant research has been done on this topic, and there is no specific legislation regarding IAQ in these locals. In this study protocol, it is proposed to determine what factors contribute to poor IAQ at Amadora Primary Health Care Center (PHCC).

Methods:
Using the environmental monitor EVM-7, PM2.5, PM10, CO2, total volatile organic compounds, temperature, and relative humidity will be measured in the treatment rooms, waiting rooms, and consultation rooms of the functional units of the PHCC of Amadora. Buildings and rooms will be characterised according to their architectural features, surroundings, and occupation, utilising the form explicitly developed for this purpose. IAQ will be described by referring to Portuguese IAQ legislation. Using the statistical analysis software Stata® 17, multilevel regression models will identify statistically significant associations between the variables.

Results:
Results are expected to provide insight into how buildings, facilities, and occupant behaviour affect IAQ at PHCC of Amadora. Additionally, they will enable the development of recommendations designed to protect patients and workers health, quality of life, and well-being.

Conclusion:
IAQ in PHCC has not been sufficiently studied, and research has been primarily focused on the hospital context and microbiological parameters. This protocol will identify architectural infrastructure and human occupation as determinants of poor IAQ in PHCCs and stimulate discussion on the need to revise Portugals air quality legislation. A collaborative approach is emphasised between the public health sector and engineering, architectural, and occupational health.