Q&A – Can the coronavirus spread through ventilation or air conditioning?
Suppose an employee is unconsciously infected with coronavirus and has no symptoms. In case of a sudden cough or sneeze, infected droplets are released. Can a ventilation or climate control system such as air conditioning spread those droplets throughout your company building? The odds are slim, although you should follow a few guidelines.
Important: for health institutions (e.g. hospitals, residential care centres) other measures apply.
In addition to touching infected surfaces or hands, the coronavirus is mainly transmitted when a person breathes in saliva droplets directly from an infected person. The known measures- keeping your distance and hand hygiene - usually protect employees adequately. That's because most droplets are so heavy that they fall to the ground straight away.
Aerosols: potential danger
But minuscule contaminated droplets - also called aerosols - can remain in the air for hours in an indoor climate. Do ventilation or climate control systems such as air conditioning not spread those droplets throughout buildings? That's unlikely, scientists now conclude. But the airflow that is created can blow contaminated aerosols further. It's not an important means of transfer, they say.
Four points for attention
In order to further minimise this limited risk, the Superior Health Council has formulated four guidelines.
- Switch off recirculation
Avoid the re-use of filtered indoor air. Virus particles circulating in the exhaust air ducts can re-enter the supply air circuit via recirculation. This is why it is better to switch the complete system to pure fresh air (see point 2) and switch off the recirculation valves.
- Provide maximum fresh air
Open windows as much as possible and - if possible - use mechanical ventilation systems. Make sure that the incoming outside air is sourced from a location where the degree of contamination of the air is as low as possible.
- Let ventilation systems run for longer
Switch on the mechanical ventilation system at least 2 hours before employees enter the workspace and allow it to work for up to 2 hours after they leave.
An individual fan is not recommended because it does not supply fresh air, but redistributes 'used' air. If such a device proves necessary, it must be aimed at an opening such as a door, not at people.
- Provide regular maintenance
Clean the ventilation and climate control system on time, install and replace filters correctly, do not skip maintenance and checks... Careful maintenance is more vital than ever.
What about parking garages?
The above guidelines also apply in parking garages. Some form of ventilation is necessary at all times.
If the supply of fresh air is impossible, recirculation is allowed. After all, the risk of CO remaining in the air in garages outweighs any possible corona contamination. Important: employees must not stay there longer than the time needed to pick up or park their vehicle.
Extra attention for sanitary facilities
Flushing the toilet, taps and sprinklers, hot air blowers... Aerosols are constantly forming in sanitary facilities. Moreover, the spaces are often small, enclosed and limited in terms of ventilation.
In order to stop the spread of covid-19, the Superior Health Council has issued three advisory reports:
- Switch off the hot air dryers and replace them with disposable paper towels.
- Ask employees to close the toilet lid before flushing.
- In closed washrooms, increase ventilation and let the ventilation work continuously. At night and during the weekend, this can be done at reduced power. For sanitary facilities with windows, continuous ventilation through the windows is sufficient.
Avoid the spread of covid-19 in the workplace
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