Maintaining optimal CO2 levels in patient wards is crucial for ensuring the health and safety of patients and healthcare staffs. This paper explores the various factors that influence CO2 levels in critical patient wards such as ICUs, burn wards, and operating theatres of Behala Balananda Brahmachari Hospital and Research Centre in Kolkata (India). Factors such as ventilation, patient density, the presence of indoor plants, room occupancy, and design are discussed. Additionally, permissible CO2 levels are examined based on guidelines from the World Health Organization (WHO), Occupational Safety and Health Administration (OSHA), and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Effective strategies for monitoring and managing CO2 levels are also outlined. The present paper has great significance as CO2 level within the healthcare units impacts the health and wellbeing of the patients.