The use of tracer gas for determining ventilation efficiency.

The local ventilation efficiency of a mechanical ventilation system may in general terms be defined as "providing air in those parts of a room where it is required". In this paper different definitions of the local ventilation efficiency and methods for measuring it are discussed. Presents results from measurements of ventilation efficiency. A test room was mechanically ventilated and nitrous oxide used as a tracer gas. A number of sensors were placed in the room with the aim of determining the variations in the air change rates within the room. Results indicate that in some cases only a minor proportion of the ventilation air flow is utilized in the occupied zone. Demonstrates that it is not advisable to use the slope of the tracer gas curves in a linear logarithmic plot as a measure of the "local ventilation rate".