7. What are the Key Environmental Factors that determine the Risk of Transmission?

• Ventilation: Inadequate ventilation results in failure of air dilution or removal of infectious droplet nuclei thereby increasing the risk of transmission.
• Duration of exposure: Spending eight continuous hours with an infectious person poses a higher risk than two hours or occasional contact.
• Concentration of the droplet nuclei: The risk of transmission is higher if the concentration of the droplet nuclei in the air is high.
• Space: The risk is higher in a small enclosed space.
• Air circulation: Recirculation of air poses a risk when it contains infectious droplets.