Laser sheet imaging as an inexpensive technique for in-situ ventilation testing

Abstract

Analyzing airflow within a room is crucial in understanding the short- and long-range transmission of aerosols. Its behavior can be influenced by several factors such as room layout, presence of furniture, air conditioning, and position of intake and exhaust vents. Current methods of determining airflow in a room rely on fog machines or CO₂ sensors, which are either expensive or lack the necessary resolution for effectiveness. We utilize the technique of laser sheet imaging to visualize the flow of the aerosol plume released from a commercially-available humidifier. Our results show that the velocity of the aerosol plume can be measured by calculating the slope of the distribution plot over time. We have also shown that the change in the plume velocity can be measured even when the source is placed at greater distances from the air purifier. Our technique can also highlight how certain types of ventilation produce spatial variations in aerosol velocity throughout the room. An exponential decay model of the decrease in intensity after the humidifier is turned off gives a time constant τ of 1.20 s. These findings suggest that this technique serves as a low-cost alternative for characterizing airflow patterns and evaluating the effectiveness of indoor ventilation systems.