## 5 Conclusions  
The outcomes of this investigation illuminate the atmospheric conditions within the Hospital Universitario Central de Asturias (HUCA) underground parking, specifically in parking level -2. They offer crucial insights into the potential health risks associated with exposure to NO and NO\({}_{2}\). The conclusions from data analysis collected across various dates and times are pivotal in shaping targeted recommendations for occupational and general user groups. The study reveals a general adherence to occupational exposure limits for NO and NO\({}_{2}\) in the hospital parking facility. However, occasional instances approached 20% of the occupational exposure limit values (OELVs), signaling the need for nuanced considerations. Environmental assessments uncovered significant concerns, with around 75% of sampled days surpassing 70% of the World Health Organization's (WHO) recommended values for maximum one-hour NO\({}_{2}\) concentrations. These environmental challenges emphasize addressing air quality concerns within healthcare parking facilities. The unique characteristics of healthcare parking facilities, catering to a diverse user base that includes vulnerable patients and children, prompt a reconsideration of current exposure limit standards designed for occupational settings. The study underscores the need for standards that better align with the varied composition of users in healthcare parking facilities. Temporal patterns in NO\({}_{2}\) concentrations, especially during peak hours, raise health concerns, particularly for individuals with respiratory conditions. The dynamic nature of NO\({}_{2}\) levels during peak hours suggests potential health risks for vulnerable populations. This underscores the importance of tailored mitigation strategies to protect users' health. Recommendations for mitigation include implementing an Enhanced Ventilation System during peak hours to reduce pollutant concentrations rapidly. Encouraging outdoor parking for vulnerable groups, especially those with respiratory issues, is crucial to mitigate exposure to harmful emissions. Introducing an Emission-Based Access Control policy during peak hours can minimize NOx accumulation. Strategic signage and awareness campaigns are proposed to inform users about health risks and discourage the use of underground parking as a waiting space. Routine monitoring and publication of findings are essential for compliance with continuous health and safety standards. Using environmental NOx values to design underground car park ventilation systems, at least in hospital facilities, is highly recommended. The study's relevance extends beyond the specific parking facility studied, as data from other hospitals with similar traffic patterns underline the importance of addressing air quality concerns, especially during heightened vehicular activity. This broader perspective emphasizes the need for comprehensive strategies to manage air quality in hospital parking facilities, contributing to the ongoing discourse on indoor air quality in healthcare settings. [PERSON] and [PERSON]; methodology, [PERSON]; validation, [PERSON], [PERSON], and [PERSON]; formal analysis, [PERSON] and [PERSON]; investigation, [PERSON], [PERSON], and [PERSON]; resources, [PERSON]; data curation, [PERSON] and [PERSON]; writing--original draft preparation, [PERSON]; writing--review and editing, all; visualization, all; supervision, all; project administration, [PERSON]; funding acquisition, [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript. This research was funded by Fundacion Prevent. Not applicable. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to confidentiality reasons. The realization of this research and the preparation of this paper were made possible through the invaluable support and collaboration of the Instituto Nacional de Silicosis.