Minimizing the spread of virus indoors

Autumn is here, temperature is dropping, storms are coming back which means that we will spend much more time indoors again. In addition to all the cozy things it brings (read – candles are lit and you have crawled up in the sofa under a blanket watching your favourite film), a boring aspect comes into the picture as well. The risk of virus spread increases.

Virus spread

Do you know that every cold origins from one of hundreds of different flu viruses? One word that has been difficult to avoid in recent times is droplets. The primary route of transmission is the inhalation of small respiratory droplets from an infected person. The droplets usually do not reach more than an arm’s distance before falling to the floor. However, smaller respiratory ‘nuclei’ from sneezing (aerosolized) can travel distances greater than 1m. Most studied viruses have a diameter between 0.01 and 0.4µm (micrometers). To put it in relation to something, a human hair is 60-120 micrometers.

This video illustrates virus spread in a good way.

What can be done to minimize the spread of virus?

Most of us have heard the guidelines of our national Public Health Agencies more or less daily since March, while other recommendations haven’t been communicated to the same degree. In our industry for example, the advice and recommendations from the organizations REHVA and Eurovent are not commonly known. Therefore, we now take the opportunity to explain them in a slightly simpler way.

Industry recommendations

As previously mentioned, viruses can be found in droplets that are so small that they remain in the air long enough to follow when the air moves indoors. Therefore, efforts should be made to keep the concentration of airborne droplets down.

To reduce the risk of the spread of virus in premises, our European industry associations recommend the following measures:

  • Maintain effective ventilation and ensure airflows. I.e. make sure that the ventilation system works according to specification. The right amount of fresh air must be supplied and bad air must be discharged via the exhaust air system.
  • Switch off any return air, so that all supply air, if possible, consists of outdoor air. Outdoor air = fresh air. That is, do not reuse and recirculate the bad air.
  • Run the ventilation in continuous operation. Alternatively, start the ventilation two hours before the room is used and continue to run two hours after the period of stay.
  • Check that the units are adjusted with the correct pressure balance and that service is performed according to the manufacturer’s instructions.
  • Change the filter as usual, i.e. when the calendar or monitoring system indicates that it is time. Follow good general practice when changing filters, so make sure that the staff use the usual protective measures: full clothing, gloves, respirator and goggles. Put the old filter in a plastic bag and seal it.

So far there are no specific recommendations for homes, but in general the same applies as for premises. That is, make sure the ventilation running, change the filter according to recommendations and ventilate extra if necessary. We can also recommend this article, which describes in a simple way how ventilation can be key to minimize the risk of spread.

If you are not sure about the right airflows into your room, you can measure the CO2 or eCO2 level as a good indicator (see blog post “How does carbon dioxide indoors affect us?”) “. Ask your ventilation installer to check the balancing of the system or install ultrasonic measurement units inside the supply ducts to check the delivered airflow. As a rule of thumb you should receive 30 to 50 m³ outdoor air per hour and person. 

Relevant links

https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub

https://www.rehva.eu/activities/covid-19-guidance

https://eurovent.eu/?q=covid19