Evaluation of infection risk by coughed air in a medical examination room: Part 1. Measurement of infection risk using tracer gas

The objective of this research is to evaluate the infection risk by the aerosol dispersion due to human cough in a medical examination room. The experiments were conducted in a full-scale test room simulated as a medical examination room. Two types of manikins were employed. One was a "Coughing Manikin," which could simulate human cough airflow using carbon dioxide (CO₂) as a tracer gas. The other was a "Thermal Manikin," which was used as a medical doctor. The thermoregulation and the breathing operation of this manikin were controlled. Seventeen conditions were examined by varying the manikin positions, airflow patterns using a push-pull ventilation system (PPVS), and other conditions. Fo r the evaluation of the infection risk, both CO₂ concentration in Thermal Manikin's breathing area and the capture efficiency of CO₂ were used. The capture efficiency was defined as the ratio of the amount of PPVS-collected CO₂ within two minutes to the total amount of CO₂ that was exchanged by Coughing Manikin. It was concluded that the PPVS influenced the decrease in the infection risk depending on the CO₂ concentration and the capture efficiency. Further, it was revealed that the PPVS arrangement is an important concern.