During the pandemic period, the hybrid work model was implemented by most companies. During the hybrid work model, we can reduce the number of employees in the office at the same time and thus reduce the risk of Covid, but not completely eliminate it.

Exposure to infected air in open offices, where most hours of the day are spent, is risky for our health. Adequate circulation of the air in the environment must be ensured. Ashrae Standards specify that the air in the office should be circulated 2-3 times per hour for a healthy working environment (Ashrae 62.2 Standard). Circulation can be achieved with natural ventilation, but the placement of the items in the environment (table, chair, bookcase, etc.) affects the circulation of the air indirectly. Uncirculated air will cause insufficient ventilation (in other words, aged air) at partial locations in the room. The risk increases in this dead zone with aged air. One of the most effective ways to eliminate this situation is to use an indoor air purifiers. Thanks to hepa filter air purifiers, which can be supplied for a few hundred dollars, the air in the environment will be cleaned and the risk of breeding infected air will be minimized.

In this study, we chose a day when our guest who came to our open office (Pazue) in Amsterdam was Covid positive, 8 people were working at the same time in the office and the weather was cold. With the cold weather, it is obvious that we will experience energy loss due to the heating requirement while circulating the air in the room with natural ventilation. For this reason, we have accepted that there are HEPA filtered air purifiers in our open office and natural ventilation cannot be used. The most important criterion here is how many times the air purifiers pass the air through its own filter and ensure this without allowing the air to age in the corner areas.

Our open Office has an area of 130m^2 and a height of approximately 2.5m. For a healthy working environment, air purifiers were used to change the air of the open office with a volume of 130m^2 x2.5m=760m^3, 2 times per hour and provide total flow rate of 325 m^3 x2=650 m^3⁄hours. Some of the infected particles coming out of our guest’s mouth will remain on the mask, some will spread to the environment as droplets, and a very small part will spread by hanging in the air. Since the weight of the CO2 gas emitted from the human mouth is heavier than the air, it mostly moves from the ground. Particles emitted from the mouth of our guest will firstly spread around themselves with the effect of body temperature. The natural convection that occurs in the environment with the effect of the body temperatures of the people in the environment, the heat coming from the glass and walls and the fresh air (leakage) coming from the stairs and under the door activates the spread in the room. As a result of natural convection movements, it shows a risky distribution in a Covid-positive environment after approximately 1 hour (Figure 2).

The operation of HEPA filtered air purifier that we place in the office will minimize the covid risky situation in the environment. In order to prevent the risky situation in the environment, we placed 2 air purifier, each with a flow rate of 380 m^3⁄hour. We compared their performance for the presence and absence of air purifiers. In order to clean the ambient air with performance, the front of the suction and blowing vents must be open. It is made possible by simulation technology to determine the placement so that the air circulation in the room is homogeneous at every point. We have positioned the air purifiers in such a way that they can absorb the polluted air in the room homogeneously and close to the areas where aged air is present.

Dirty particles emitted from the mouth of our covid positive guest coming to our open office will be minimized by air purifiers with hepa filters. Thus, the risk of Covid for others in the indoor environment is reduced.

The use of masks shows high performance in eliminating viruses that are likely to spread with droplets. However, the importance of HEPA filter air purifier is different. The density of infected particles that cannot be prevented by the mask and spread by mixing with the ambient air is diluted to a minimum by air purifiers. Thus, the amount of contamination is reduced and the air in the environment is in accordance with the standards. We can watch the condition of the air purifiers before and after the operation in the video below.