Integral analysis of indoor environmental quality in a hemodialysis unit: Indoor air quality and airborne diseases relative risk

• Monitoring the indoor environment is vital for health in hemodialysis units. • HCHO, C 6 H 6 , O 3 , PM, CO 2 , Ta and RH were analyzed under two ventilation modes. • Mechanical ventilation kept CO₂ below 800 ppm, reducing airborne transmission risk. • Optimized ventilation balances air quality and thermal comfort. • Mechanical ventilation, RH control, and masks mitigate virus spread in HD unit. Monitoring indoor environmental quality (IEQ) is essential in healthcare facilities, particularly in hemodialysis (HD) units where vulnerable patients remain for 4–5 h per session several times per week. This study conducted an integrated assessment of hygrothermal comfort, indoor air quality (IAQ), and airborne infection risk in an HD unit under two scenarios: natural ventilation and controlled mechanical ventilation (CMV). IAQ was evaluated through CO 2 , benzene, formaldehyde, ozone, and particulate matter (PM 0.3 , PM 2.5 , PM 10 ), while hygrothermal comfort was monitored via air temperature and humidity, Relative infection risk was estimated using CO₂-based modeling adapted from the Wells–Riley approach. Results showed that CMV maintained CO₂ below 800 ppm, meeting Spanish regulatory standards, whereas natural ventilation was insufficient despite high envelope permeability. PM 2.5 and PM 10 remained within WHO guidelines, but peaks of PM 0.3 were observed, emphasizing the need for finer particle control. Infection risk was strongly influenced by activity level and mask use, with healthcare workers posing greater risk than patients. Deficient filter maintenance compromised pollutant removal, occasionally increasing PM during CMV operation. These findings highlight the necessity of optimized and well-maintained ventilation systems to balance air quality, comfort, and infection control in HD environments, offering methodological insights extendable to other healthcare settings.