Background: Among hospitals-related health risks, environmental factors play a key-role; this accounting for different rooms' specific use, patients' vulnerability and risk of overcrowding. For these reasons, air control in hospitals and in healthcare facilities in general deserves scientific attention. Objective: Assessing of the quality of indoor air ventilation in critical care department hospitals and its effect on the incidence of hospital acquired infections in order to optimize the ventilation methods in hospitals. Patients and methods: Our study was performed in Egypt by correlating the examined 70 air samples, from the Intensive Care Unit (ICU), Cardiac Care Unit (CCU) and Neonatal Intensive Care Unit (NICU) in one of the General Organization of Teaching Hospitals and Institute, for presence of bacterial and fungal contamination with the concomitant infection of 70 patients admitted in these units during the period from November 2019 to January 2020. Results: We had 59 (84.2%) positive air samples in comparison to 21 (30%) positive endotracheal tube (ETT) fluid culture and 19 (27.1%) positive blood cultures in the completely selected air sampling areas and in the selected patients during the included sampling period. This suggested a strong relation between the contamination between the indoor airs either by bacterial or fungal organisms, and between the concomitant presence of the same organism in the ETT fluid samples and to lesser extent in the blood cultures. Conclusion: This study has fortified the hypothesis that achieving an optimal level of indoor air quality is related to applying the infection control rules, application of approved air filters and strict adherence to hand hygiene.