A portable unit for measuring ventilation efficiency

A computerised portable unit for measuring the ventilation efficiency by the tracer gas technique is described. The hardware of the unit is designed from readily available equipment. The software of the unit is menu-driven to be operated by computer non-experts. The software include several analytical models of ventilation processes and in the present study, age analysis and the air exchange efficiency are discussed. In a field study the ventilation process of a non-occupied lecture hall was characterised by the portable unit, and in case of almost isothermal conditions the measured air exchange efficiency was 54% indicating mixing. It is emphasised that the portable unit may also be used for characterising the indoor air pollution.