Sealed housing for evaporative determination

This rule is justified by the need to limit the benzene emissions from evaporation (Tims, 1983) Figure 5.25 shows that emissions increase linearly with the benzene content of the fuel. It is noteworthy that current legislation limits the measured evaporation to 2 g per test conducted in accordance with a standard procedure (Sealed Housing for Evaporative Determination, or SHED). Yet for a fuel containing 5% benzene, an evaporation of 0.7 g benzene /test is observed. 

SHED = Sealed Housing for Evaporative Determination. Gasoline vehicles only. 

California law prescribes a limit of 0.5 g/test for the sum of evaporative emissions from a motor vehicle beginning with model year 2004. Compliance with the limits must be confirmed by defined testing methods. In the 3-day diurnal test, for example, evaporative emissions from the entire vehicle are measured over a 3-day period in a SHED (Sealed Housing for Evaporative Determination) test chamber subjected to a predefined, 24-h temperature stress program (from 18.3 to 40.6 °C). After each 24-h period, the concentration of hydrocarbons (HC in ppm) is measured and converted into HC equivalents (in grams). The highest of the three measured values is then the test result. 

Legislation has also imposed increased demands on the elastomers used for automobile sealants. Most notable has been environmental legislation to reduce primary pollutants. The US Sealed Housing for Evaporative Determination and the European Euro 2000 legislative projects, which called for dramatic reductions in fugitive emissions, are two examples of this. 

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