Developments in a multi-tracer gas system and measurements using portable SF6 equipment.

In this paper we describe the development of a multi-tracer gas system for measuring interzonal air movement in buildings. The system consists of simple and stand-alone gas injectors and sampling units. The injectors are capable of releasing up to four perfluorocarbon tracer gases in different parts of a building. Following tracer gas injection and mixing, small samples of air are collected using automatic sampling units. Each unit consists of a 16-position valve and a group of removable stainless steel tubes packed with solid absorbent. Samples may be taken simultaneously at up to four points in space and up to 16 points in time. These samples are then stored for subsequent analysis in the laboratory using an automatic thermal desorber and gas chromatograph. In the second part of the paper, the portable sulphur hexafluoride (SF6) system is described, The system incorporates an electron capture detector gas chromatograph and operates automatically using a BBC microcomputer. Using this system the air change rates were measured in a number of recently constructed houses in the Milton Keynes area, UK. The test data of various measurements are presented together with an analysis of the results.