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GreenFlag certification: the foundation

GreenFlag Association research is based on top rated global science that shows the importance of ventilation in public spaces to peoples’ health and safety. We assess all the “barriers” in the defence system against pathogens, such as the COVID-19 virus, but emphasise that ventilation is the key area.

Our assessments involve measuring carbon dioxide concentrations in a specific area as it has been shown that the concentration of carbon dioxide levels can be used as a proxy for the levels of other possible contaminants in the air.

Proper ventilation is one of the most important tools to ensure the circulation of clean air in a space, thereby clearing out possible pollutants.

GreenFlag certification will not be issued if ventilation controls are inadequate.

Why use ventilation as the cornerstone criteria for GreenFlag certification?

  • Ventilation is the most neglected barrier to the spread of disease
  • 25% of COVID-19 infections are linked to the fomite route
  • Studies show lower transmission infections attributed to the fomite route (about 16%)
  • Aerosol transmission of COVID-19 is probably the most important route of transmission
  • Virus-laden aerosols frequently infect susceptible contacts at close proximity where they are most concentrated — like smoke
  • The main “universal” barriers to transmission in public spaces now importantly include ventilation

CO2 as a surrogate gas for estimating Covid-19 Infectious Dose in an occupied space

Green Flag CO2
  • Studies have correlated high CO2 levels to poor indoor air quality, increased absenteeism, loss of productivity and poor decision making

  • 800 parts per million CO2 roughly equates to 15 liters per second per person

  • A CO2 value maintained as <400ppm above ambient (outside) air limits viral transmission (99.9% risk reduction)

  • CO2 is considered a surrogate gas that represents poor ventilation

  • Any additional CO2 is generated by occupants

  • Ambient (outside) CO2 concentrations vary according to the environment. Approximate reference values are: Rural areas = 350ppm, small towns = 400ppm, city centers = 450ppm)32.

Air change rates required to maintain a given CO2 concentration in a typical office with 20 people breathing normally

CO2 Concentration
CO2 Concentration