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? This is highly unlikely provided you follow a few important 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 a distance, face masks, coughing and sneezing into the crook of the elbow or preferably a paper tissue (and then discarding it) 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. Ventilation and climate control systems create airflow that can further spread the contaminated aerosols.
5 points for attention
In order to stop the spread of aerosols, the Superior Health Council has issued four guidelines.
- Provide maximum fresh air
Supplying fresh, uncontaminated air lowers the concentration of virus particles in the air.
The use of mechanical ventilation systems is preferable and should enable 100% fresh air. 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. The ventilation flow rate should be at least 50 m³, and preferably 80 m³, of fresh air per hour per person.
If mechanical ventilation is not an option, keep the windows and doors on one side of the room open at all times. This is the only way to obtain a higher ventilation rate. To further increase the circulation of fresh air, you can open windows on different walls. However, avoid uncontrolled airflow between different rooms, especially from rooms with potentially high concentrations of virus particles, such as sanitary facilities, to ’cleaner’ rooms like offices.
It is essential to limit the number of persons in a room so that the CO2 concentration remains under 800 ppm (CO indicates the degree to which the air quality in a closed space is influenced by the number of persons present who may be a carrier of the coronavirus).
- 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 bestto switch the complete system to pure fresh air and switch off the recirculation valves.
If this is not possible, ensure the filtration of therecirculated air. The best option is to purify the circulation air through central filtration. If possible, use HEPA filters and electrostatic precipitators. Other disinfection methods (UV-C, ozone, etc.) are not recommended due to, among other reasons, possible health risks for people.
Circulation air filtration can by no means replace proper ventilation. It only partly compensates for insufficient ventilation at best.
- Let ventilation systems run for longer
Switch on the mechanical ventilation system at least two hours before employees enter the workspace and allow it to work for up to two hours after they leave.
- Ensure regular maintenance
Clean the ventilation and climate control system regularly, install and replace filters correctly, do not skip maintenance and inspections, and so on. Careful maintenance is more vital than ever.
Read our tips for optimal maintenance of air conditioning in the workplace here.
- Avoid other air movement systems
Air movement systems other than ventilation systems increase the risk of spreading aerosols. The Superior Health Council advises against their use. If this is unavoidable, increase the supply of fresh outside air and make sure that the air from the system is not directed at the people working in the space.
- An individual ventilator must be placed close to an open window to ensure that this fresh outside air is blown into the room. When it comes to hot air blowers or air heaters, it is recommended to increase the supply of fresh air by opening windows and doors and to keep the warm airflow from blowing directly on people.
- Jet hand dryers should be avoided at all cost, as they contribute to the production of aerosols. Do not allow them to be used and replace them with paper towels. (see also: sanitary supplies)
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 coronavirus 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, etc. 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 the coronavirus, 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 run 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
A question? Contact us on +32 2 549 71 00 or mail us. We are happy to help.