b a modest elevation change of 1000 feet e g from birmingham to new orleans will result in an atmospheric pressure difference of 0 5 psia or 13 8 inches of water c an elevation change of 3000 feet e g from los angeles to san jose will result in an atmospheric pressure difference of 1 5 psia or 41 4 inches of water d a significant elevation difference of 4000 feet e g from el paso to houston will result in an atmospheric pressure difference of 2 0 psia or 55 2 inches of water and e an even more significant but entirely possible elevation difference of 5000 feet e g from albuquerque to phoenix will only result in an atmospheric pressure difference of 2 5 psia or 69 0 inches of water therefore a pressure variation of about 2 5 psia or less is the source of the problems with air cell growth and rupture that is leading to the shrinkage problems it is clear that a pressure variation of 2 5 psia during shipping is far too extreme and must be reduced significantly one embodiment of a proposed solution to this problem may be understood by way of an example to start the analysis assume that the gases involved obey the ideal gas law pv mrt m where p pressure v total volume m mass r universal gas constant t temperature m molecular weight therefore if everything remains constant except for the pressure and the molecular weight the volume would be next assume a maximum elevation change of 2000 feet occurs during transportation then assume that the frozen dessert is manufactured at the point of lowest elevation and that.