Why indoor air quality matters even more now

by | 21 Aug 2020 | Products

Did you know that air quality indoors can be 2-5 times worse than outdoors?

Now that the summer season is in full swing and businesses and restaurants are slowly reopening after the corona crisis, it is especially important to pay attention to indoor air quality. Ventilation systems and an adequate air-exchange rate can help to clean indoor environments from contaminants – including viruses.

A single sneeze or cough can contain up to 200 million viral particles. In a short time, those exposed to it can receive a thousand virions, which is enough to lead to an infection. The viral load of an infected person can vary. The largest and heaviest drops fall to the ground almost immediately, while the others can remain suspended in the air, spreading more easily in indoor environments and reaching every point of the room*.

The use of ventilation systems in spaces such as hotels, restaurants, bars, shops, offices and gyms, has been demonstrated to be an effective solution to protect people from the spread of SARS-CoV-2 during this pandemic. Business owners should therefore consider ventilation as a preventive measure to protect both their business and their customers.

It is important to understand that ventilation systems need to be operated and maintained correctly, in order for them to be effective. To get the most out of your ventilation system, it is important to carry out regular maintenance activities including filter and duct cleaning.

Ventilation systems need to be properly designed and sized in order to guarantee the adequate air-exchange rate in the indoor environment and properly clean the air. Using highly efficient filters and regular maintenance of the installed systems (incl. filter replacement & duct cleaning) will help to ensure the highest level of air filtration and optimal ventilation system performance.

Another important aspect is related to the level of filtration of the outdoor air that the systems can guarantee. Since we do not want to introduce outdoor contaminants into indoor environments during the air exchange process, it is important that ventilation systems can adequately filter and clean the outdoor air using highly efficient filters.

Air-exchange is another key factor to be considered when checking ventilation system performance.

There is a close correlation between the ventilation-rate and infection possibility. That means the higher the ventilation rate per hour is in a room, the lower is the possibility of infection for the occupants.

This has been clearly demonstrated by a US study**, which indicates that, once an asymptomatic infector who has not been identified as confirmed COVID-19 patient enters a public confined space, there is a 2% probability of infection at the common ventilation rate (500-2500 m3 /h). If we consider the case of a restaurant for example were people usually spend from 2 to 4 hours, for instance, we know that to keep the probability of infection between occupants at 1%, we need 2.4 ACH (/h) (air change per hour) if occupants are not wearing masks, while 0.6 ACH (/h) is enough if occupants are wearing masks. Of course, to keep the probability of infection even lower, a higher ACH is needed.

So, once an asymptomatic infector enters a public confined space, the risk of infection for other occupants is quite high if there is no adequate ventilation rate in the building, or there is no ventilation at all. Therefore, it is fundamental to make sure that the ventilation system is properly sized and can provide the right exchange rate per hour.


*The Risks – Know Them – Avoid Them”, https://www.erinbromage.com/post/the-risks-know-them-avoid-them

**Association of infected probability of COVID-19 with ventilation rates in confined spaces: A Wells-Riley equation-based investigation” https://www.medrxiv.org/content/10.1101/2020.04.21.20072397v1

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  • Dawn Studler
  • [email protected]
  • Daikin Central Europe
  • Did you know that air quality indoors can be 2-5 times worse than outdoors?