Primary objective of air-conditioning is to create an indoor air quality and thermal condition of comfort suitable for persons / patients, with minimum energy cost. In air-conditioning system, ventilation airflow rate is the amount of fresh outdoor air introduced into the room to dilute CO2, contaminants and odours etc. Numerical model solves mass, momentum and energy equations. The contaminated particle (infection) which is simulated with a Lagrangian particle tracking model and the same has been carried out by simulation. This is usually a small part of the supply airflow rate which is introduced and distributed into the room at proper flow rate, velocity, temperature and relative humidity so as to remove the thermal loads and obtain conditions of thermal comfort. This is filtered to remove contaminants, mixed with ventilation air and conditioned by cooling / heating and humidifying / dehumidifying before introduction into the room. The study concerns about the health risk of the airborne diseases (bacteria, fungus, viruses etc.) from the patient to the other people in the ICU of hospital. By observing the movement of contaminated particle, it is advisable to keep the nurse-station and health care staff near the inlet to keep them healthy.