Why care for indoor air?

Outbreak at an office

office, call center

The Office, South Korea

Following an outbreak of Covid-19 in an office in Seoul, South Korea, authorities initiated a research team to analyze the outbreak and learn more about the causes of the spread of the infection. The conclusion about the outbreak in this 19-storey office building showed that the risk of infection had increased manifold due to four key factors:

  • Closeness 
  • Long-term contact
  • Many people
  • Enclosed space 

Let’s take a closer look at the process


The outbreak was concentrated to one department. A call center on one of the floors. The staff in the department worked together in an open office landscape, where each table had 13 workplaces.

office, tested positive

On some desks, such as this one, 9 of the 13 employees tested positive

office, enclosed space

These employees were sitting inside an enclosed space with 137 workers.

office, 79 tested positive

Out of these 137 employees, 79 (57.6%) tested positive. The permanent contact within the same space over a prolonged period of time played a crucial role.

office, other employees

Far fewer of the other employees on this floor tested positive.

office, rest of building

In the rest of the building, only 3 people tested positive out of 927 who underwent checks (0.3%) despite the fact they shared lobbies, elevators and other communal areas.

Conclusions of the research report

The research report carried out by local authorities showed that almost all the people who became infected in this 19-storey building (with more than a thousand office workers) were confined to the call center. In addition, the infected people worked almost exclusively in the same room. Despite the significant contact between employees from different floors of the building, the spread of the virus was largely limited to the only space filled with employees sitting at desks. This indicates that closeness was probably the main reason for the widespread spread.

How do we minimize the spread of infection in offices and workplaces

Recommendations from researchers and health experts aim to reduce the risk by avoiding larger collections of people. We need to reduce the concentration of people and also the exposure time, i.e. the time they spend together.

How it can be avoided

  • switch to teleworking
  • use facemasks
  • don’t share material and equipment between co-workers
  • keep staff distanced by 
    • avoid large meetings 
    • keep down the number of people at entrances / exits / elevators and in dining rooms / cafeterias
    • organize workstations in a zig-zag pattern and maintain a distance of two meters between each 
  • make sure that the spaces are well ventilated and that the ventilation is kept running. WHO, ECDC and others recommend that ventilation is running two hours before and two hours after the working day for contaminants and infectious agents to be ventilated out
  • avoid recirculation of air
  • if the building doesn’t have a ventialtion system, open windows frequently for fresh air

Links to similar studies and analyzes

Interested in further dialogue?

Get in touch!


  1. El País, https://english.elpais.com/society/2020-10-28/a-room-a-bar-and-a-class-how-the-coronavirus-is-spread-through-the-air.html, https://english.elpais.com/spanish_news/2020-06-17/an-analysis-of-three-covid-19-outbreaks-how-they-happened-and-how-they-can-be-avoided.html, Authors: Javier Salas (javier@esmateria.com), Mariano Zafra
  2. US Centers for Disease Control and Prevention, Centers for Disease Control and Prevention in Guangzhou and Hangzhou, The Johns Hopkins Center for Health Security, the Spanish National Research Council’s Institute of Environmental Assessment and Water Studies (IDAEA-CSIC), European Centre for Disease Prevention and Control, International Laboratory for Air Quality & Health (WHO, Queensland), and the government of South Korea.

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