There is evidence that the public can react strongly against the disturbance caused by fumes from traffic, particularly in urban areas. An initial step in an investigation into the ways of reducing vehicle exhaust odour is to develop a method of quantifying the odour levels leading to this subjective reaction; for this purpose, a research contract was let to the imperial college of science and technology for the identification of the malodorous components of exhaust gases. A method has been developed for the collection and the analysis of street air for the estimation of odour levels. The sample is collected on a polymeric adsorbent at ambient temperatures and then eluted by a standardised procedure for chromatographic and mass spectral analysis. This method leads to the detection of hydrocarbons with carbon numbers of six or more, and is particularly sensitive in the c8 to c10 region. Oxygen-, sulphur-, and nitrogen-containing compounds were not detected. The levels in street air were, on average, below the odour threshold levels, although it is probable that fluctuations do occur which exceed the threshold. Measurements were made in the ventilation system of a vehicle travelling in convoy on an urban motorway; these levels, on average, exceeded the odour threshold level. The composition of the exhaust from petrol, diesel and jet engine was analysed and it was found that the composition of the exhaust closely paralleled the composition of the fuel. Further investigation is being made into the odour problems and, in particular, the quantification of odour levels in street air at various intensities of and compositions of traffic. (Author/publisher)
Abstract