Despite the existence of legislation, confined spaces continue to be a concern for industries. The aim of this article is to investigate atmospheric risks in confined spaces at construction sites and condominiums during the construction process, as well as during cleaning, maintenance, and repair interventions. To this end, a research questionnaire was applied to characterize confined spaces, a checklist was used to assess how risks are being monitored and controlled, and measurements were taken with fast-response sensors to analyze the presence of atmospheric risks. The research revealed deficiencies in meeting the minimum requirements of the legislation, such as the absence of safety procedures, registries, trained rescue teams, as well as the lack of atmosphere evaluation and ventilation and/or exhaust systems. Measurements of oxygen concentrations and levels analyzed gases O2, CO, CO2, H2S, and LEL. It can be concluded that despite the measured atmospheres not showing significant alterations, additional risks and surroundings should be considered, such as falls from height, which pose a danger to the health or life of workers during confined space activities.