Contamination risks evaluated with the lr-method in unidirectional airflow at different air velocities
Journal article, 2019

Operating rooms for patients undergoing infection-prone surgery often have unidirectional flow supply air systems. Many systems installed in Europe have low air velocities, i.e. equal and below 0.3 m/s, while other supply air systems have velocities about 0.4 m/s. The velocity, given by the supplier, is mostly the inlet air velocity just below the filter screen of the unidirectional flow system. The purpose of this paper is to describe contamination risks in unidirectional airflow without obstacles at different air velocities. To evaluate contamination risks, the method for limitation of risks, the LR-Method, has been used. The results show that the convection flows and arm movements from a person standing in the unidirectional airflow system have a great impact on the contamination risks at air velocities below 0.4 m/s and that the air velocity should at least be 0.4 m/s to achieve a good protection efficacy.

Air velocity

Unidirectional airflow

Risk assessment



Bengt Ljungqvist

Chalmers, Architecture and Civil Engineering, Building Services Engineering

Johan Nordenadler

Karolinska University Hospital

Berit Reinmüller

Chalmers, Architecture and Civil Engineering, Building Services Engineering

European Journal of Parenteral and Pharmaceutical Sciences

09644679 (ISSN) 17406277 (eISSN)

Vol. 24 2 44-48

Subject Categories

Energy Engineering

Building Technologies

More information

Latest update