Abstract
The statistical treatment was pursued for determination of average emission rates of polynuclear aromatic hydrocarbons (PAH) from a single automobile. Intermittent sampling (20 samples at random intervals) from the same car gave a broad distribution for PAHemission rate, while continual sampling (20 successive samples during a continuous run ofthe car) gave a narrow distribution. The average of PAH emission rates from the intermittent sampling will reflect the average emission rate characteristic of an individual automobile. A linear relation between the standard deviation and the mean of PAH emission rates was obtained for each sampling method, and the quasi-constancy of the standard deviation of the logarithm of PAH emission rate was observed regardless of the difference of cars, operating conditions, mileages and species of PAH. The sampling errors for the average determined from n intermittent samples were estimated as follows. n=5:±17%, n=12% and n=20:±8%. The broad distribution of PAH emission rate by the intermittent sampling seems to result from the fluctuations of the consumption rate of engine oil.
