| Abstract
| - One hundred three in-use vehicles identified as highhydrocarbon and/or carbon monoxide emitters by remotesensing and roadside visual, underhood checks duringa 1995 South Coast Air Quality Management District programwere tested on the IM240 cycle using a transportabledynamometer. Seventy-one of these vehicles wererepairedas part of the program and were retested. Seventeenvehicles in the fleet initially emitted visible smoke fromthetailpipe and were classified as “smokers”. Thefleetranged in age from 6 to 22 years, with a median age of12.3years. Exhaust HC, CO, NOx, and particulateemissions (PM-10) were measured. PM-10 mass and the elemental andcarbonaceous composition of the particulate matter weredetermined. The average fleet PM-10 emission rate was0.138 g/mi, while the average emission rate for smokerswas 0.395 g/mi. It was concluded that the casualobservationof smoking vehicles was not very successful in identifyinghigh PM-10 emitting vehicles. The particulate mattercomposition was primarily carbonaceous, with a variabledistribution between the elemental and organic carbonfractions, and showed no significant difference in thepercentorganic carbon fraction between smokers and non-smokers.The PM composition differed, on average, betweenpre-repair and post-repair samples. The effect of theCalifornia Smog Check repair program on PM emission ratescould not be evaluated due to concerns regarding theeffect of vehicle conditioning on these measurements.
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