Analysis: as we prepare to return to offices and schools, here's what can be done to remove the virus from the air around us
Ventilation is a key factor for reducing the spread of Covid-19 in buildings and other enclosed spaces, such as vehicles. It helps to remove the virus from the air, thereby lowering the risk of airborne transmission. Ventilation in the workplace is especially important because many people are often sharing the same air and infections can therefore spread more easily.
With schools, colleges and many offices reopening soon, people should be looking at ways to improve ventilation in the workplace (if they have not done so already) so here's a five point plan to improve ventilation in your workplace
(1) Checks and inspections
Check ventilation using this handy ventilation checklist provided by the Health and Safety Authority (HSA). Inspect your workplace and ensure that windows are not painted over or sealed shut, wall vents are fully open, fans work, dampers are set correctly and that air filters are changed regularly. Pay special attention to areas where more people congregate.
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From RTÉ Brainstorm, why clean air is key to preventing the spread of Covid-19
(2) Improve ventilation
Maximise the intake of outdoor air and use extraction fans to improve ventilation. Avoid the recirculation of indoor air as it could also recirculate the virus. For more detailed information on improving mechanical ventilation consult the Work Safely Protocol.
(3) Optimise natural ventilation
Open doors and windows opposite to each other to create a flow of fresh air across the indoor space. Open high level windows where available to provide ventilation without draughts. If possible, maintain openings throughout the day to allow a constant flow of fresh air.
(4) Monitor ventilation
Carbon dioxide (CO2) exists in exhaled air and it can indicate that ventilation is not sufficient if the amount in an indoor space builds up. A CO2 monitor with a non-dispersive infrared (NDIR) detector can help you identify poorly ventilated areas. Background outdoor levels of CO2 are around 420 ppm. If the CO2 level in a room exceeds 800 ppm, more should be done to improve the flow of fresh air.
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From RTÉ Radio 1's Drivetime, Prof John Wenger on why carbon dioxide monitors may be a key tool in the great reopening
(5) Enhance removal of the virus from poorly ventilated spaces
You can do this by using a High Efficiency Particulate Air (HEPA) filter device. Portable units that combine a HEPA filter with a powered fan system are the preferred option for additional air cleaning. Users need to select a device that can handle the volume of air in the location where it is installed. The use of ozone generators and devices based on other technologies such as ionizers, plasmas or photochemical oxidation is currently not recommended as they have a limited evidence base and may generate undesirable secondary chemical products that could lead to health effects.
Please remember that ventilation should be used along with face coverings, physical distancing and hygiene in a layered approach to minimising the spread of Covid-19. The "Swiss Cheese" model captures the layered approach very well.
The science of airborne transmission
Coronavirus is present in tiny particles emitted from the mouth when an infected person is breathing, talking, singing, coughing or sneezing. These tiny particles do not fall to the ground, but remain suspended in the air as aerosols for up to several hours. If someone breathes in virus-containing particles that are suspended in the air, they can become infected with Covid-19. This is known as airborne transmission.
Airborne transmission is very important indoors, particularly in poorly ventilated spaces where levels of the virus can spread throughout the room and build up over time. Under these conditions, there is no safe distance from an infected person and all those present are at increased risk of infection.
Because coronavirus is spread through the air, it is useful to think of the virus-containing particles acting like cigarette smoke. Ventilation will remove the virus from the air as it would cigarette smoke.
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From RTÉ Radio 1's News At One, Cian McCormack reports on calls for changes to building standards for high density and build-to-rent apartments because inadequate ventilation and crowed buildings pose an infection risk during a pandemic
Airborne transmission is by far the most plausible way in which the virus is transmitted during "superspreading events", where one infected person (frequently asymptomatic) spreads the virus to many others. Airborne transmission of the virus can be greatly reduced by ensuring that there is sufficient ventilation to clear the air.
What is ventilation?
Ventilation is the supply of outside air into a building to replace stale or polluted indoor air. It may be provided by natural or mechanical means or a combination of both.
Natural Ventilation is driven by the natural forces of wind and temperature difference and can be achieved by opening windows, doors and wall vents.
Mechanical Ventilation systems deliver outside air in a controlled way through a combination of fans and ducts.
Prof John Wenger is Chair of the Irish Government's Expert Group on the Role of Ventilation in Reducing Transmission of Covid-19.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
