instrumentation

Describes a photo-electric technique for instant determination of contaminant concentration in wind tunnel studies of stack gas dispersion. A roving sensor is used to measure the light scattered by the particles of oily aerosol representing theprototype stack effluent. The minature probe has a noise level of only one hundred thousandth of the full linear range of the output signal for a time constant of 5s. Device is also suitablefor measurement of fluctuating flow properties, such as turbulence, where a high frequency response is required.

Describes the basis of operation of electron absorption detector and the nature and causes of the erroneous and anomalous responses it may generate. Suggests pulse sampling technique asan alternative method of analysis. This retains the sensitivity of the simple low potential ion chamber method, but is substantially free of errors and anomolous responses. Describes the basis of this improved method and gives an account of the technique for its use in quantitative and qualitative analysis.

Gives formula for calculating air-change-rate from decay rate of a tracer gas. Discusses different tracer gases and detecting instruments. Describes portable meter used to measure the concentration of helium. Discusses its performance and describes the experimental procedure.

Describes a pressure transducer which was specially developed to measure wind pressures exerted in buildings. The instrument, which gives an electrical output, is suitable for measuring pressure in the range of 1200 n/m2. The frequency response enables pressure fluctuations lasting only 0.1 s to be recorded.

Reports project to measure wind pressures on low-rise buildings. Describes site and houses in the estate selected for investigation. Gives details of an associated experimental building. Outlines positioning of the pressure transducers andgives details of the cabling and the reference pressure system. describes velocity measurement, recording equipment and methods of calibration, processing and analysis. Gives details of records taken in tabular form.

Describes instrumentation used to measure wind pressure on two tall buildings in central London. Describes pressure transducer which gives an electrical output suitable for use in conjunction with standard types of commercial recording equipment. Describes site installation and recording equipment which produces multi-channel records in ultra-violet sensitive photographic paper. The records are processed and digitised and several computer programs have been written to analyse this data.

Gives theoretical justification for the use of tracer gas method for measuring air infiltration. Describes automated instrumentation system using sulphur hexafluoride as a tracer gas. The system consists of an electron capture detector, an automation unit, an SF6 storage and injection panel, a cassette recorder and corresponding plumbing and tanks. Gives examples of field use of system.

Describes a system which measures the rate of air infiltration in buildings using sulphur hexafluoride as a tracer gas. Discusses two methods for evaluating the infiltration rate,the decay method and the constant concentration method. The system automatically operates a portable electron capture detector /chromatograph and samples air on a one-minute cycle. In the decay method the slope of concentration vs time on a semilogarithmic plot can be used to compute infiltration rate.

Reviews use of tracer compounds to demonstrate the transfer of pollutants from one local area or city to another. A study of gaseous compounds resulted in the selection of three suitable materials:sulphur hexafluoride, bromotrifluoromethan andOctafluorocyclobutane. These materials are all non-toxic, rare in the atmosphere and can be readily dispersed from tanks.Describes two systems developed to detect tracer gases. Sensitivity of 10-5 p.p.m. was achieved for sulphur hexafluoride without concentration of the sample. Gives method for collectingair samples and analysing them.

Describes operation of thermal imaging cameras with a display monitor detecting infra-red radiation. Since temperature differentials of 0.20C are significant for insulation of buildings, camera must be used to limits of its sensitivity and monitoring procedure must be carefully chosen. Treats measurement limitations in field of building. Uses details of thermographic surveys to illustrate some difficulties of measurement and analysis. Emphasises importance of correct inspection procedures for particular situation.