BRE has developed a new technique for measuring time-averaged ventilation rates in occupied buildings using a perfluorocarbon tracer gas. It was conceived as a way of solving the problems which arise when conventional tracer gas techniques are used in large or multi-roomed buildings. Potentially, the new technique will allow routine performance monitoring of both natural ventilation and forced air supply systems, thereby helping users to save energy and to meet the health, safety and comfort requirements of the building's occupants.
With the improvement of thermal building Insulation the percentage of energy losses due to air exchange becomes an increasingly· important factor in building energy demand. In order to optimize infiltration and ventilation and to minimize the energy demand of low energy buildings, it is necessary to install an appropriate mechanical ventilation system. Different ventilation strategies can be used: Extract ventilation and supply I extract ventilation systems for buildings as well as single-zone ventilation units with or without heat recovery.
Trouble shooting air distribution problems in mechanically ventilated offices often has to be carriedout in limited "after hours" periods. The method of applying a pulse of tracer to the fresh air supplyhas been found to be too time consuming to map the local mean age of air over complex floor plans.In response an automated gas chromatograph has been developed to make air change efficiencymeasurements in real time using the method of homogeneous emission.
A passive tracer gas technique - the homogenous emission technique was utilised formeasuring the air distribution in a part of an office building with displacement ventilation.Measurements were made during one winter period and one summer period. During thewinter period the ventilation was run continuously, while on/off regulation was used duringthe summer period.
The use of the laboratory fume hood as the primary containment device in the laboratory has been a standard practice for almost half a century. Quantitative testing of the performance of these devices, however; is a more recent discipline. The use of the ANSI/ASHRAE 110-1995, Method of Testing Performance of Laboratory Fume Hoods (ASH RAE 1995) is becoming a standard specification in the purchase of new fume hoods, the commissioning of new laboratory facilities, and benchmarking fume hoods in existing facilities.
This paper reports on the ventilation measurements in a cinema using the tracer-gas technique. Both the local and room air exchange efficiencies were measured. The two tracer-gas methods, "step-up" and "step-down (decay)", were used alternately when the cinema was in use to enable a continuous measurement of air-exchange efficiencies under various occupancies. The air exchange efficiencies were found to be very close to that for a perfect mixing, with little influence from the occupants. This might be due to that the cinema had a downward mixing ventilation with a large air change rate.
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