08.07.2016 change 08.07.2016

What escapes between the door and frame?

How do contaminants heavier than air flow between rooms when you open the door? Until now, this issue has not been thoroughly studied. Scientists from the Warsaw University of Technology took up the topic. The issue is not as trivial as it may seem. The research will helps to understand how to better protect operating theatres, isolation and clean rooms.

These are areas where the air must be especially protected. This includes clean rooms in biochemical laboratories, operating theatres, hospital isolation and clean rooms. To prevent that air in such rooms from mixing with the air outside, you can vary the pressure in those rooms. It does not always look the same.

Operating theatres and clean rooms need to be protected from external contamination. Therefore, the pressure in these rooms is higher than outside. As a result, when opening the door, due to the pressure equalization the air flows outside, limiting the penetration inside by, for example, dust or bacteria. Opposite solution is applied in modern hospital isolation in which patients are treated infectious diseases. To prevent dangerous microorganisms from escaping from the room with the air, the pressure in isolation is lower than on the outside. As a result, when the door opens the air flows inward, preventing the spread of pathogens. Pressure differences are not large - up to half hectopascals, but this is usually enough.

Until now, however, not much was known about the role of the motion of door opening and closing in the transfer of contaminants heavier than air between different rooms. New study conducted at the Faculty of Building Services, Hydro and Environmental Engineering, Warsaw University of Technology, sheds light on this issue. The results have been published in the journal "PLOS".

The study shows what should be taken into account when building spaces that need to be protected against the flow of contaminants and how to most effectively use the infrastructure that already exists.

The authors explained in an interview with PAP that in the study they used heavy smoke generators, which were placed in the room with the lower pressure - the one from which smoke should not escape. They checked how much smoke would enter the other room when opening the door.

"We wanted to see how contaminants heavier than air would move during the movement of the door. This has not been verified before" - the researchers explained. According to them, air movement that occurs at this point is not without significance.

In rooms with hinged doors - which are more common - air mixing at the entrance is much more intense than in the case of sliding doors. The dynamics of entering the room is also significant. "Most contaminants are transferred between the rooms separated by a hinged door - while moving the door, fast opening and closing" - they noted.

PAP - Science and Scholarship in Poland, Ludwika Tomala

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