Apparatus and method for determining evaporative emissions

摘要

A sealed housing evaporative determination (SHED) apparatus and method for practically zero emission vehicles (PZEV) provides periodic sampling of ambient air within a substantially air-tight testing structure enclosing a vehicle under test. Pressure drops within the testing structure are compensated by injecting air substantially free of hydrocarbons into the testing structure. Pressure increases within the testing structure are reduced by withdrawing ambient air from the testing structure. Hydrocarbon content of any withdrawn ambient air is determined from the latest sample, and cumulative evaporative emissions are adjusted accordingly.