Method of designing a fuel vapor pressure management apparatus

A fuel vapor pressure management apparatus of a fuel system supplying fuel to an internal combustion engine, the fuel vapor pressure management apparatus performing leak detection on a headspace of the fuel system, the apparatus comprising:

• a housing defining an interior chamber;
• a pressure operable device separating the interior chamber into first and second portions, the pressure operable device including a seal and a poppet cooperatively engaging the seal with a contact force, the seal includes a first effective area equal to a difference between a first area defined by a major perimeter and a second area defined by a minor perimeter, and the poppet is movable along an axis and includes a second effective area defined by the minor perimeter of the seal;
• and
• a switch positioned in the second portion of the interior chamber, the switch requiring an activation force to actuate the switch;
• wherein a first pressure level at which excess negative pressure is relieved is calculated by dividing the contact force by the first effective area, and a second pressure level at which excess positive pressure is relieved is calculated by dividing the activation force by the second effective area.