Evaporative Emissions Standards

Evaporative emissions from motor vehicles account for approximately half of the reactive organic gas (ROG) motor vehicle emission inventory in the state, and are classified into three types - running loss, hot soak and diurnal emissions.

• Running loss emissions occur when the vehicle is driven.
• Hot soak emissions occur immediately after a fully-warmed up vehicle is stationary with the engine turned off.
• Diurnal (daily, happening every day) emissions occur when a vehicle is parked and are caused by daily ambient temperature changes. Most of these emissions result during increasing ambient temperatures which cause an expansion of the vapor in the fuel tank.