The Transmission Of COVID Through Aerosols

The relationship between ventilation and the airborne transmission of COVID has been in the news over the last few months. Is this something that you should be considering? The simple answer is a resounding YES! A research article titled ‘A guideline to limit indoor airborne transmission of COVID-19’ says: ‘Airborne transmission arises through the inhalation of aerosol droplets exhaled by an infected person and is now thought to be the primary transmission route of COVID-19.’ ¹

We now understand more about the transmission of COVID and how it spreads via airborne particles and droplets. We know that aerosols dependent on size can remain airborne for hours and that the risk is far higher indoors, and in shared spaces, where dilution ventilation using outside air is inadequate.

Given the importance of ventilation in reducing the risk of airborne transmission, conducting a Ventilation Assessment (especially of shared indoor spaces in workplaces, entertainment venues, apartment buildings, schools and hospitals) should be high on your list of priorities.

General COVID-19 Considerations

COVID-19 is able to be transmitted through the air via aerosols or droplets being expired by one person and inhaled (or contacting the mouth, nose or eyes) of another. The generation of aerosols can be increased through coughing, sneezing, exercising or talking, with other vocal activities such as yelling and singing likely to increase the risk of aerosol generation.

Fans, air conditioning systems, people moving and natural ventilation as well as the initial force generating the aerosol will all influence an aerosol’s movement in a room.

In a COVID environment, the objective is to limit recirculation of (untreated) exhaled air as far as practicable. This will generally be best achieved by increasing the volume of fresh air entering and expired air leaving the room.

Ventilation Considerations

There are several factors to consider when deciding on the ventilation needed in shared spaces:

• How much fresh air does the space have?
  Little natural ventilation will need to be supplemented by mechanical ventilation
• Type of Current HVAC System
  Ducted HVAC or individual split systems
• How many people use or occupy the area?
  The more people who use or occupy an area, the greater the risk that an infected person is there
• How large is the area?
  The larger the area, the lower the risk
• What tasks or activities take place in the area?
  Activities that make you breathe deeper, for example physical exertion or shouting, will increase the transmission risk
• Are there any features in the workplace that affect ventilation? 
  Large machinery, equipment or pillars/posts can prevent air circulating and create pockets of stagnant air

A Ventilation Assessment

A Ventilation Assessment will establish the current state of your ventilation and identify opportunities to improve ventilation with the aim of reducing the potential COVID-19 transmission through direct and recirculated aerosol contact. It will include:

• A review of fixed heating, ventilation and air conditioning systems and arrangements
• A review of proposed administrative arrangements for occupancy and risk management
• Provision of a report detailing the findings of the investigation and recommendations to reduce the risk of airborne COVID 19 transmission including options for additional air filtration and treatment where required
• Provision of recommendations for the monitoring of the effectiveness of ventilation systems and controls following occupancy