The measurement of air infiltration rates in large enclosures and buildings.

The paper describes work carried out as part of a research contract funded by the U.K. Department of the Environment and the Commission of the European Communities. The object of the research is to develop a validated method of measuring air infiltration rates in industrial buildings and to use the method to measure ventilation rates in some selected buildings. The following points are discussed: (a) Poor mixing in industrial buildings. implications of poor mixing for choice of measurement method and interpretation of results. (b) Review of possible measurement methods. Trials of a low cost fuel cell gas analyser designed for measuring ethanol vapour. (c) A computer-controlled multi-point tracer gas concentration measurement system using infra-red gas analysers and 'nitrous oxide as the tracer gas. (d) Preliminary results obtained with only natural venti 1 ati on. (e) Need to validate method by comparing ventilation rates measured by tracer gas method with mechanical extract or supply rates while depressurising or pressurising a test enclosure. Airtightness testing of two industrial buildings in preparation for validation work.