The cough-jets of an infected person expels droplets that fall within a short distance and aerosol plumes that could follow the airflow streamlines generated by the AC . The path can be altered by moving objects, including doctors and patients, leading to unpredictable spread of the viral-laden particles. 

Model #1: Aerosol and Droplet Behavior in Healthcare Center

Ceiling fans provide local mechanical ventilation, and by the process of convection, warm air (and virus-laden particles expelled by infected patients) travels upwards. However, without adequate openings to allow the virus-laden particles to exit the building, others become more susceptible to infection.

Model #2: Aerosol and Droplet Behavior in Healthcare Center

- Model #1

- Model #2

(The numbering does not indicate prioritization)

Smith College

- cabin of airplane

- interior space of car

- dormitory-type space of healthcare or isolation center

Effect of Confined Space on SARS-CoV-2-laden Aerosol and Droplet Behavior

Airflow model in Healthcare Center with AC on and all openings closed

Aerodynamics in Healthcare Center (AC + no opening)

Examples of medical procedures that cause aerosol transmission:
- endotracheal intubation

- bronchoscopy

- open suctioning

- administration of nebulized treatment
 
- manual ventilation before intubation

- turning the patient to the prone position

- disconnecting the patient from the ventilator

- non-invasive positive-pressure ventilation

- tracheotomy

- cardiopulmonary resuscitation


Aerosol Transmission via Medical Procedures

Airflow model in Healthcare Center with ceiling fans and all openings closed;


Air travels downward, sweeping against people and objects. Through convection, warm air moves up towards the ceiling.

Aerodynamics in Healthcare Center (ceiling fans + no opening)

A cough expelled at 10 m/s can cause droplets to travel four to five seats ahead and one seat behind. This experiment predicts that 5-10 people could get infected due to droplet spread with an infected person on board. Aerosol  plumes may affect far more but the extent to which aerosol plumes can infect susceptible hosts is still poorly understood. 

Aerosol and Droplet Behavior in Cabin of Airplane

Aerosol and Droplet Behavior in Car Interior Space

Aerosol and Droplet Behavior in Healthcare Setting

Noninvasive ventilators are generally discouraged for critically ill patients with acute respiratory distress syndrome (ARDS) due to COVID-19. Non-invasive positive-pressure ventilation increases the risk of droplet spread due to inappropriate mask fitting. 
They are based on the bag valve mask design based on manual tidal volume adjusted for patient use.

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