The transmission of an explosion of a plant component into another can be prevented, if both are separated by a sufficiently narrow gap.
according to BG Chemie R 003 6/2000
The standard gap is determined as the largest width of a gap with a length of 25 mm between two parts of a calibration set-up.
Under prescribed conditions the inflammations of the gas mixture inside present does not lead to inflammation of the gas mixture outside present.
It has to be validated for all concentration ranges of the examined gas or steam in air.
The standard gap is very important for the ignition protection class of the pressure resistant packaging and for the interpretation of flame barriers.