The air flow in a doorway is governed by density difference caused by temperature difference and pressure difference caused by mechanical ventilation. Tests have been carried out in a unique indoor test house where the room to room to temperature difference could be controlled very accurately with a new control system. In addition to these tests some tests were carried out in a scale model with water as the operating fluid. Two main criteria of unidirectional flow in a doorway have been explored:
- The recorded mean velocity is unidirectional
- The neutral height is equal to the height of the door
- Unidirectional flow in the sense that there is no transfer of contaminant from one room to another.
To explore condition one the velocity profile in the doorway have been recorded by transversing the door opening. Condition two has been explored by using tracer gas technique.