Abstract
Exhaled contaminants transported in the air can result in the transmission of many airborne infectious diseases in indoor environments. When the exhaled air from the infected person directly enters the breathing zone of another person, direct exposure occurs. When the exhaled contaminants disperse in the room and then are inhaled by another person, indirect exposure occurs. This investigation developed a method for differentiating the direct and indirect exposure to exhaled contaminants in indoor environments with mechanical ventilation. A literature review was conducted to collect experimental data for 191 person-to-person contaminant transport cases. With the analysis of the database, a mathematical method was developed to differentiate direct and indirect exposure in rooms with mixing and displacement ventilation systems. The proposed method correctly differentiated direct and indirect exposure for 120 out of the 133 mixing ventilation cases and 47 out of the 58 displacement ventilation cases. It can be used at the early design stage to quickly assess whether there will be direct exposure to exhaled contaminants in a room with mechanical ventilation systems.
Highlights
The airborne transmission of infectious diseases in indoor environments has been become a major public health concern worldwide [1]
An infected person can exhale particles carrying infectious viruses which can be transported to the breathing zone of other persons via the air and cause cross infection
Indirect exposure occurs when contaminants disperse in the room and are inhaled by the target person
Summary
The airborne transmission of infectious diseases in indoor environments has been become a major public health concern worldwide [1]. An infected person can exhale particles carrying infectious viruses which can be transported to the breathing zone of other persons via the air and cause cross infection. Many outbreaks of airborne infectious diseases have occurred indoors through this transmission route. It is crucial to investigate the indoor exposure to exhaled contaminants in mechanically ventilated rooms to improve air distribution design and reduce the risk of infection. Direct exposure occurs when the exhaled jet carrying contaminants from the source person directly enters the breathing zone of the target person. Direct exposure is determined primarily by the impact scope of the exhaled air [5]. Indirect exposure occurs when contaminants disperse in the room and are inhaled by the target person. Indirect exposure is determined primarily by the ventilation in the room
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