A nominal gap is not enough
Large doors, fabricated frames and removable containers rarely present one perfect clearance. Measure the perimeter in the closed operating position and record both the smallest and largest values.
Separate repeatable tolerance from faults
The seal can accommodate a designed range, but it should not be expected to correct a loose hinge, distorted door or improperly positioned container. Repair mechanical faults before sizing the seal around them.
Check the retracted envelope
The profile needs room to expand and room to withdraw. Verify the uninflated seal does not rub during the full motion of the equipment or product.
Test the worst credible combination
Prototype testing should include the largest gap, smallest gap, most demanding corner and expected temperature condition. Record the complete fixture and pressure-control settings so the result can be repeated.