A vehicle can emit hydrocarbons both when the engine is running and when turned off. For that reason, tank venting systems were introduced to relieve pressure in the tank (e.g., because of fuel heating in summer) by expelling emissions into the air. This also allows hydrocarbons to escape. These emissions are now restricted and must therefore be monitored. This is achieved using SHED measurements.
The SHED test cabin is an airtight room from which air samples are taken for analysis. The test specimen can either be an entire vehicle or just individual components.
